diff options
| -rw-r--r-- | Documentation/spi/spi-summary | 416 | ||||
| -rw-r--r-- | arch/arm/Kconfig | 2 | ||||
| -rw-r--r-- | drivers/Kconfig | 2 | ||||
| -rw-r--r-- | drivers/Makefile | 1 | ||||
| -rw-r--r-- | drivers/spi/Kconfig | 76 | ||||
| -rw-r--r-- | drivers/spi/Makefile | 23 | ||||
| -rw-r--r-- | drivers/spi/spi.c | 568 | ||||
| -rw-r--r-- | include/linux/spi/spi.h | 542 |
8 files changed, 1630 insertions, 0 deletions
diff --git a/Documentation/spi/spi-summary b/Documentation/spi/spi-summary new file mode 100644 index 0000000..00497f9 --- /dev/null +++ b/Documentation/spi/spi-summary @@ -0,0 +1,416 @@ +Overview of Linux kernel SPI support +==================================== + +22-Nov-2005 + +What is SPI? +------------ +The "Serial Peripheral Interface" (SPI) is a four-wire point-to-point +serial link used to connect microcontrollers to sensors and memory. + +The three signal wires hold a clock (SCLK, often on the order of 10 MHz), +and parallel data lines with "Master Out, Slave In" (MOSI) or "Master In, +Slave Out" (MISO) signals. (Other names are also used.) There are four +clocking modes through which data is exchanged; mode-0 and mode-3 are most +commonly used. + +SPI masters may use a "chip select" line to activate a given SPI slave +device, so those three signal wires may be connected to several chips +in parallel. All SPI slaves support chipselects. Some devices have +other signals, often including an interrupt to the master. + +Unlike serial busses like USB or SMBUS, even low level protocols for +SPI slave functions are usually not interoperable between vendors +(except for cases like SPI memory chips). + + - SPI may be used for request/response style device protocols, as with + touchscreen sensors and memory chips. + + - It may also be used to stream data in either direction (half duplex), + or both of them at the same time (full duplex). + + - Some devices may use eight bit words. Others may different word + lengths, such as streams of 12-bit or 20-bit digital samples. + +In the same way, SPI slaves will only rarely support any kind of automatic +discovery/enumeration protocol. The tree of slave devices accessible from +a given SPI master will normally be set up manually, with configuration +tables. + +SPI is only one of the names used by such four-wire protocols, and +most controllers have no problem handling "MicroWire" (think of it as +half-duplex SPI, for request/response protocols), SSP ("Synchronous +Serial Protocol"), PSP ("Programmable Serial Protocol"), and other +related protocols. + +Microcontrollers often support both master and slave sides of the SPI +protocol. This document (and Linux) currently only supports the master +side of SPI interactions. + + +Who uses it? On what kinds of systems? +--------------------------------------- +Linux developers using SPI are probably writing device drivers for embedded +systems boards. SPI is used to control external chips, and it is also a +protocol supported by every MMC or SD memory card. (The older "DataFlash" +cards, predating MMC cards but using the same connectors and card shape, +support only SPI.) Some PC hardware uses SPI flash for BIOS code. + +SPI slave chips range from digital/analog converters used for analog +sensors and codecs, to memory, to peripherals like USB controllers +or Ethernet adapters; and more. + +Most systems using SPI will integrate a few devices on a mainboard. +Some provide SPI links on expansion connectors; in cases where no +dedicated SPI controller exists, GPIO pins can be used to create a +low speed "bitbanging" adapter. Very few systems will "hotplug" an SPI +controller; the reasons to use SPI focus on low cost and simple operation, +and if dynamic reconfiguration is important, USB will often be a more +appropriate low-pincount peripheral bus. + +Many microcontrollers that can run Linux integrate one or more I/O +interfaces with SPI modes. Given SPI support, they could use MMC or SD +cards without needing a special purpose MMC/SD/SDIO controller. + + +How do these driver programming interfaces work? +------------------------------------------------ +The <linux/spi/spi.h> header file includes kerneldoc, as does the +main source code, and you should certainly read that. This is just +an overview, so you get the big picture before the details. + +There are two types of SPI driver, here called: + + Controller drivers ... these are often built in to System-On-Chip + processors, and often support both Master and Slave roles. + These drivers touch hardware registers and may use DMA. + + Protocol drivers ... these pass messages through the controller + driver to communicate with a Slave or Master device on the + other side of an SPI link. + +So for example one protocol driver might talk to the MTD layer to export +data to filesystems stored on SPI flash like DataFlash; and others might +control audio interfaces, present touchscreen sensors as input interfaces, +or monitor temperature and voltage levels during industrial processing. +And those might all be sharing the same controller driver. + +A "struct spi_device" encapsulates the master-side interface between +those two types of driver. At this writing, Linux has no slave side +programming interface. + +There is a minimal core of SPI programming interfaces, focussing on +using driver model to connect controller and protocol drivers using +device tables provided by board specific initialization code. SPI +shows up in sysfs in several locations: + + /sys/devices/.../CTLR/spiB.C ... spi_device for on bus "B", + chipselect C, accessed through CTLR. + + /sys/bus/spi/devices/spiB.C ... symlink to the physical + spiB-C device + + /sys/bus/spi/drivers/D ... driver for one or more spi*.* devices + + /sys/class/spi_master/spiB ... class device for the controller + managing bus "B". All the spiB.* devices share the same + physical SPI bus segment, with SCLK, MOSI, and MISO. + +The basic I/O primitive submits an asynchronous message to an I/O queue +maintained by the controller driver. A completion callback is issued +asynchronously when the data transfer(s) in that message completes. +There are also some simple synchronous wrappers for those calls. + + +How does board-specific init code declare SPI devices? +------------------------------------------------------ +Linux needs several kinds of information to properly configure SPI devices. +That information is normally provided by board-specific code, even for +chips that do support some of automated discovery/enumeration. + +DECLARE CONTROLLERS + +The first kind of information is a list of what SPI controllers exist. +For System-on-Chip (SOC) based boards, these will usually be platform +devices, and the controller may need some platform_data in order to +operate properly. The "struct platform_device" will include resources +like the physical address of the controller's first register and its IRQ. + +Platforms will often abstract the "register SPI controller" operation, +maybe coupling it with code to initialize pin configurations, so that +the arch/.../mach-*/board-*.c files for several boards can all share the +same basic controller setup code. This is because most SOCs have several +SPI-capable controllers, and only the ones actually usable on a given +board should normally be set up and registered. + +So for example arch/.../mach-*/board-*.c files might have code like: + + #include <asm/arch/spi.h> /* for mysoc_spi_data */ + + /* if your mach-* infrastructure doesn't support kernels that can + * run on multiple boards, pdata wouldn't benefit from "__init". + */ + static struct mysoc_spi_data __init pdata = { ... }; + + static __init board_init(void) + { + ... + /* this board only uses SPI controller #2 */ + mysoc_register_spi(2, &pdata); + ... + } + +And SOC-specific utility code might look something like: + + #include <asm/arch/spi.h> + + static struct platform_device spi2 = { ... }; + + void mysoc_register_spi(unsigned n, struct mysoc_spi_data *pdata) + { + struct mysoc_spi_data *pdata2; + + pdata2 = kmalloc(sizeof *pdata2, GFP_KERNEL); + *pdata2 = pdata; + ... + if (n == 2) { + spi2->dev.platform_data = pdata2; + register_platform_device(&spi2); + + /* also: set up pin modes so the spi2 signals are + * visible on the relevant pins ... bootloaders on + * production boards may already have done this, but + * developer boards will often need Linux to do it. + */ + } + ... + } + +Notice how the platform_data for boards may be different, even if the +same SOC controller is used. For example, on one board SPI might use +an external clock, where another derives the SPI clock from current +settings of some master clock. + + +DECLARE SLAVE DEVICES + +The second kind of information is a list of what SPI slave devices exist +on the target board, often with some board-specific data needed for the +driver to work correctly. + +Normally your arch/.../mach-*/board-*.c files would provide a small table +listing the SPI devices on each board. (This would typically be only a +small handful.) That might look like: + + static struct ads7846_platform_data ads_info = { + .vref_delay_usecs = 100, + .x_plate_ohms = 580, + .y_plate_ohms = 410, + }; + + static struct spi_board_info spi_board_info[] __initdata = { + { + .modalias = "ads7846", + .platform_data = &ads_info, + .mode = SPI_MODE_0, + .irq = GPIO_IRQ(31), + .max_speed_hz = 120000 /* max sample rate at 3V */ * 16, + .bus_num = 1, + .chip_select = 0, + }, + }; + +Again, notice how board-specific information is provided; each chip may need +several types. This example shows generic constraints like the fastest SPI +clock to allow (a function of board voltage in this case) or how an IRQ pin +is wired, plus chip-specific constraints like an important delay that's +changed by the capacitance at one pin. + +(There's also "controller_data", information that may be useful to the +controller driver. An example would be peripheral-specific DMA tuning +data or chipselect callbacks. This is stored in spi_device later.) + +The board_info should provide enough information to let the system work +without the chip's driver being loaded. The most troublesome aspect of +that is likely the SPI_CS_HIGH bit in the spi_device.mode field, since +sharing a bus with a device that interprets chipselect "backwards" is +not possible. + +Then your board initialization code would register that table with the SPI +infrastructure, so that it's available later when the SPI master controller +driver is registered: + + spi_register_board_info(spi_board_info, ARRAY_SIZE(spi_board_info)); + +Like with other static board-specific setup, you won't unregister those. + + +NON-STATIC CONFIGURATIONS + +Developer boards often play by different rules than product boards, and one +example is the potential need to hotplug SPI devices and/or controllers. + +For those cases you might need to use use spi_busnum_to_master() to look +up the spi bus master, and will likely need spi_new_device() to provide the +board info based on the board that was hotplugged. Of course, you'd later +call at least spi_unregister_device() when that board is removed. + + +How do I write an "SPI Protocol Driver"? +---------------------------------------- +All SPI drivers are currently kernel drivers. A userspace driver API +would just be another kernel driver, probably offering some lowlevel +access through aio_read(), aio_write(), and ioctl() calls and using the +standard userspace sysfs mechanisms to bind to a given SPI device. + +SPI protocol drivers are normal device drivers, with no more wrapper +than needed by platform devices: + + static struct device_driver CHIP_driver = { + .name = "CHIP", + .bus = &spi_bus_type, + .probe = CHIP_probe, + .remove = __exit_p(CHIP_remove), + .suspend = CHIP_suspend, + .resume = CHIP_resume, + }; + +The SPI core will autmatically attempt to bind this driver to any SPI +device whose board_info gave a modalias of "CHIP". Your probe() code +might look like this unless you're creating a class_device: + + static int __init CHIP_probe(struct device *dev) + { + struct spi_device *spi = to_spi_device(dev); + struct CHIP *chip; + struct CHIP_platform_data *pdata = dev->platform_data; + + /* get memory for driver's per-chip state */ + chip = kzalloc(sizeof *chip, GFP_KERNEL); + if (!chip) + return -ENOMEM; + dev_set_drvdata(dev, chip); + + ... etc + return 0; + } + +As soon as it enters probe(), the driver may issue I/O requests to +the SPI device using "struct spi_message". When remove() returns, +the driver guarantees that it won't submit any more such messages. + + - An spi_message is a sequence of of protocol operations, executed + as one atomic sequence. SPI driver controls include: + + + when bidirectional reads and writes start ... by how its + sequence of spi_transfer requests is arranged; + + + optionally defining short delays after transfers ... using + the spi_transfer.delay_usecs setting; + + + whether the chipselect becomes inactive after a transfer and + any delay ... by using the spi_transfer.cs_change flag; + + + hinting whether the next message is likely to go to this same + device ... using the spi_transfer.cs_change flag on the last + transfer in that atomic group, and potentially saving costs + for chip deselect and select operations. + + - Follow standard kernel rules, and provide DMA-safe buffers in + your messages. That way controller drivers using DMA aren't forced + to make extra copies unless the hardware requires it (e.g. working + around hardware errata that force the use of bounce buffering). + + If standard dma_map_single() handling of these buffers is inappropriate, + you can use spi_message.is_dma_mapped to tell the controller driver + that you've already provided the relevant DMA addresses. + + - The basic I/O primitive is spi_async(). Async requests may be + issued in any context (irq handler, task, etc) and completion + is reported using a callback provided with the message. + + - There are also synchronous wrappers like spi_sync(), and wrappers + like spi_read(), spi_write(), and spi_write_then_read(). These + may be issued only in contexts that may sleep, and they're all + clean (and small, and "optional") layers over spi_async(). + + - The spi_write_then_read() call, and convenience wrappers around + it, should only be used with small amounts of data where the + cost of an extra copy may be ignored. It's designed to support + common RPC-style requests, such as writing an eight bit command + and reading a sixteen bit response -- spi_w8r16() being one its + wrappers, doing exactly that. + +Some drivers may need to modify spi_device characteristics like the +transfer mode, wordsize, or clock rate. This is done with spi_setup(), +which would normally be called from probe() before the first I/O is +done to the device. + +While "spi_device" would be the bottom boundary of the driver, the +upper boundaries might include sysfs (especially for sensor readings), +the input layer, ALSA, networking, MTD, the character device framework, +or other Linux subsystems. + + +How do I write an "SPI Master Controller Driver"? +------------------------------------------------- +An SPI controller will probably be registered on the platform_bus; write +a driver to bind to the device, whichever bus is involved. + +The main task of this type of driver is to provide an "spi_master". +Use spi_alloc_master() to allocate the master, and class_get_devdata() +to get the driver-private data allocated for that device. + + struct spi_master *master; + struct CONTROLLER *c; + + master = spi_alloc_master(dev, sizeof *c); + if (!master) + return -ENODEV; + + c = class_get_devdata(&master->cdev); + +The driver will initialize the fields of that spi_master, including the +bus number (maybe the same as the platform device ID) and three methods +used to interact with the SPI core and SPI protocol drivers. It will +also initialize its own internal state. + + master->setup(struct spi_device *spi) + This sets up the device clock rate, SPI mode, and word sizes. + Drivers may change the defaults provided by board_info, and then + call spi_setup(spi) to invoke this routine. It may sleep. + + master->transfer(struct spi_device *spi, struct spi_message *message) + This must not sleep. Its responsibility is arrange that the + transfer happens and its complete() callback is issued; the two + will normally happen later, after other transfers complete. + + master->cleanup(struct spi_device *spi) + Your controller driver may use spi_device.controller_state to hold + state it dynamically associates with that device. If you do that, + be sure to provide the cleanup() method to free that state. + +The bulk of the driver will be managing the I/O queue fed by transfer(). + +That queue could be purely conceptual. For example, a driver used only +for low-frequency sensor acess might be fine using synchronous PIO. + +But the queue will probably be very real, using message->queue, PIO, +often DMA (especially if the root filesystem is in SPI flash), and +execution contexts like IRQ handlers, tasklets, or workqueues (such +as keventd). Your driver can be as fancy, or as simple, as you need. + + +THANKS TO +--------- +Contributors to Linux-SPI discussions include (in alphabetical order, +by last name): + +David Brownell +Russell King +Dmitry Pervushin +Stephen Street +Mark Underwood +Andrew Victor +Vitaly Wool + diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 50b9afa..3cfd82a 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -729,6 +729,8 @@ source "drivers/char/Kconfig" source "drivers/i2c/Kconfig" +source "drivers/spi/Kconfig" + source "drivers/hwmon/Kconfig" #source "drivers/l3/Kconfig" diff --git a/drivers/Kconfig b/drivers/Kconfig index 48f446d..283c089 100644 --- a/drivers/Kconfig +++ b/drivers/Kconfig @@ -44,6 +44,8 @@ source "drivers/char/Kconfig" source "drivers/i2c/Kconfig" +source "drivers/spi/Kconfig" + source "drivers/w1/Kconfig" source "drivers/hwmon/Kconfig" diff --git a/drivers/Makefile b/drivers/Makefile index 7fc3f0f..7c45050 100644 --- a/drivers/Makefile +++ b/drivers/Makefile @@ -41,6 +41,7 @@ obj-$(CONFIG_FUSION) += message/ obj-$(CONFIG_IEEE1394) += ieee1394/ obj-y += cdrom/ obj-$(CONFIG_MTD) += mtd/ +obj-$(CONFIG_SPI) += spi/ obj-$(CONFIG_PCCARD) += pcmcia/ obj-$(CONFIG_DIO) += dio/ obj-$(CONFIG_SBUS) += sbus/ diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig new file mode 100644 index 0000000..d310510 --- /dev/null +++ b/drivers/spi/Kconfig @@ -0,0 +1,76 @@ +# +# SPI driver configuration +# +# NOTE: the reason this doesn't show SPI slave support is mostly that +# nobody's needed a slave side API yet. The master-role API is not +# fully appropriate there, so it'd need some thought to do well. +# +menu "SPI support" + +config SPI + bool "SPI support" + help + The "Serial Peripheral Interface" is a low level synchronous + protocol. Chips that support SPI can have data transfer rates + up to several tens of Mbit/sec. Chips are addressed with a + controller and a chipselect. Most SPI slaves don't support + dynamic device discovery; some are even write-only or read-only. + + SPI is widely used by microcontollers to talk with sensors, + eeprom and flash memory, codecs and various other controller + chips, analog to digital (and d-to-a) converters, and more. + MMC and SD cards can be accessed using SPI protocol; and for + DataFlash cards used in MMC sockets, SPI must always be used. + + SPI is one of a family of similar protocols using a four wire + interface (select, clock, data in, data out) including Microwire + (half duplex), SSP, SSI, and PSP. This driver framework should + work with most such devices and controllers. + +config SPI_DEBUG + boolean "Debug support for SPI drivers" + depends on SPI && DEBUG_KERNEL + help + Say "yes" to enable debug messaging (like dev_dbg and pr_debug), + sysfs, and debugfs support in SPI controller and protocol drivers. + +# +# MASTER side ... talking to discrete SPI slave chips including microcontrollers +# + +config SPI_MASTER +# boolean "SPI Master Support" + boolean + default SPI + help + If your system has an master-capable SPI controller (which + provides the clock and chipselect), you can enable that + controller and the protocol drivers for the SPI slave chips + that are connected. + +comment "SPI Master Controller Drivers" + depends on SPI_MASTER + + +# +# Add new SPI master controllers in alphabetical order above this line +# + + +# +# There are lots of SPI device types, with sensors and memory +# being probably the most widely used ones. +# +comment "SPI Protocol Masters" + depends on SPI_MASTER + + +# +# Add new SPI protocol masters in alphabetical order above this line +# + + +# (slave support would go here) + +endmenu # "SPI support" + diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile new file mode 100644 index 0000000..afd2321 --- /dev/null +++ b/drivers/spi/Makefile @@ -0,0 +1,23 @@ +# +# Makefile for kernel SPI drivers. +# + +ifeq ($(CONFIG_SPI_DEBUG),y) +EXTRA_CFLAGS += -DDEBUG +endif + +# small core, mostly translating board-specific +# config declarations into driver model code +obj-$(CONFIG_SPI_MASTER) += spi.o + +# SPI master controller drivers (bus) +# ... add above this line ... + +# SPI protocol drivers (device/link on bus) +# ... add above this line ... + +# SPI slave controller drivers (upstream link) +# ... add above this line ... + +# SPI slave drivers (protocol for that link) +# ... add above this line ... diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c new file mode 100644 index 0000000..7cd356b --- /dev/null +++ b/drivers/spi/spi.c @@ -0,0 +1,568 @@ +/* + * spi.c - SPI init/core code + * + * Copyright (C) 2005 David Brownell + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#include <linux/autoconf.h> +#include <linux/kernel.h> +#include <linux/device.h> +#include <linux/init.h> +#include <linux/cache.h> +#include <linux/spi/spi.h> + + +/* SPI bustype and spi_master class are registered during early boot, + * usually before board init code provides the SPI device tables, and + * are available later when driver init code needs them. + * + * Drivers for SPI devices started out like those for platform bus + * devices. But both have changed in 2.6.15; maybe this should get + * an "spi_driver" structure at some point (not currently needed) + */ +static void spidev_release(struct device *dev) +{ + const struct spi_device *spi = to_spi_device(dev); + + /* spi masters may cleanup for released devices */ + if (spi->master->cleanup) + spi->master->cleanup(spi); + + class_device_put(&spi->master->cdev); + kfree(dev); +} + +static ssize_t +modalias_show(struct device *dev, struct device_attribute *a, char *buf) +{ + const struct spi_device *spi = to_spi_device(dev); + + return snprintf(buf, BUS_ID_SIZE + 1, "%s\n", spi->modalias); +} + +static struct device_attribute spi_dev_attrs[] = { + __ATTR_RO(modalias), + __ATTR_NULL, +}; + +/* modalias support makes "modprobe $MODALIAS" new-style hotplug work, + * and the sysfs version makes coldplug work too. + */ + +static int spi_match_device(struct device *dev, struct device_driver *drv) +{ + const struct spi_device *spi = to_spi_device(dev); + + return strncmp(spi->modalias, drv->name, BUS_ID_SIZE) == 0; +} + +static int spi_uevent(struct device *dev, char **envp, int num_envp, + char *buffer, int buffer_size) +{ + const struct spi_device *spi = to_spi_device(dev); + + envp[0] = buffer; + snprintf(buffer, buffer_size, "MODALIAS=%s", spi->modalias); + envp[1] = NULL; + return 0; +} + +#ifdef CONFIG_PM + +/* Suspend/resume in "struct device_driver" don't really need that + * strange third parameter, so we just make it a constant and expect + * SPI drivers to ignore it just like most platform drivers do. + * + * NOTE: the suspend() method for an spi_master controller driver + * should verify that all its child devices are marked as suspended; + * suspend requests delivered through sysfs power/state files don't + * enforce such constraints. + */ +static int spi_suspend(struct device *dev, pm_message_t message) +{ + int value; + + if (!dev->driver || !dev->driver->suspend) + return 0; + + /* suspend will stop irqs and dma; no more i/o */ + value = dev->driver->suspend(dev, message); + if (value == 0) + dev->power.power_state = message; + return value; +} + +static int spi_resume(struct device *dev) +{ + int value; + + if (!dev->driver || !dev->driver->resume) + return 0; + + /* resume may restart the i/o queue */ + value = dev->driver->resume(dev); + if (value == 0) + dev->power.power_state = PMSG_ON; + return value; +} + +#else +#define spi_suspend NULL +#define spi_resume NULL +#endif + +struct bus_type spi_bus_type = { + .name = "spi", + .dev_attrs = spi_dev_attrs, + .match = spi_match_device, + .uevent = spi_uevent, + .suspend = spi_suspend, + .resume = spi_resume, +}; +EXPORT_SYMBOL_GPL(spi_bus_type); + +/*-------------------------------------------------------------------------*/ + +/* SPI devices should normally not be created by SPI device drivers; that + * would make them board-specific. Similarly with SPI master drivers. + * Device registration normally goes into like arch/.../mach.../board-YYY.c + * with other readonly (flashable) information about mainboard devices. + */ + +struct boardinfo { + struct list_head list; + unsigned n_board_info; + struct spi_board_info board_info[0]; +}; + +static LIST_HEAD(board_list); +static DECLARE_MUTEX(board_lock); + + +/* On typical mainboards, this is purely internal; and it's not needed + * after board init creates the hard-wired devices. Some development + * platforms may not be able to use spi_register_board_info though, and + * this is exported so that for example a USB or parport based adapter + * driver could add devices (which it would learn about out-of-band). + */ +struct spi_device *__init_or_module +spi_new_device(struct spi_master *master, struct spi_board_info *chip) +{ + struct spi_device *proxy; + struct device *dev = master->cdev.dev; + int status; + + /* NOTE: caller did any chip->bus_num checks necessary */ + + if (!class_device_get(&master->cdev)) + return NULL; + + proxy = kzalloc(sizeof *proxy, GFP_KERNEL); + if (!proxy) { + dev_err(dev, "can't alloc dev for cs%d\n", + chip->chip_select); + goto fail; + } + proxy->master = master; + proxy->chip_select = chip->chip_select; + proxy->max_speed_hz = chip->max_speed_hz; + proxy->irq = chip->irq; + proxy->modalias = chip->modalias; + + snprintf(proxy->dev.bus_id, sizeof proxy->dev.bus_id, + "%s.%u", master->cdev.class_id, + chip->chip_select); + proxy->dev.parent = dev; + proxy->dev.bus = &spi_bus_type; + proxy->dev.platform_data = (void *) chip->platform_data; + proxy->controller_data = chip->controller_data; + proxy->controller_state = NULL; + proxy->dev.release = spidev_release; + + /* drivers may modify this default i/o setup */ + status = master->setup(proxy); + if (status < 0) { + dev_dbg(dev, "can't %s %s, status %d\n", + "setup", proxy->dev.bus_id, status); + goto fail; + } + + /* driver core catches callers that misbehave by defining + * devices that already exist. + */ + status = device_register(&proxy->dev); + if (status < 0) { + dev_dbg(dev, "can't %s %s, status %d\n", + "add", proxy->dev.bus_id, status); +fail: + class_device_put(&master->cdev); + kfree(proxy); + return NULL; + } + dev_dbg(dev, "registered child %s\n", proxy->dev.bus_id); + return proxy; +} +EXPORT_SYMBOL_GPL(spi_new_device); + +/* + * Board-specific early init code calls this (probably during arch_initcall) + * with segments of the SPI device table. Any device nodes are created later, + * after the relevant parent SPI controller (bus_num) is defined. We keep + * this table of devices forever, so that reloading a controller driver will + * not make Linux forget about these hard-wired devices. + * + * Other code can also call this, e.g. a particular add-on board might provide + * SPI devices through its expansion connector, so code initializing that board + * would naturally declare its SPI devices. + * + * The board info passed can safely be __initdata ... but be careful of + * any embedded pointers (platform_data, etc), they're copied as-is. + */ +int __init +spi_register_board_info(struct spi_board_info const *info, unsigned n) +{ + struct boardinfo *bi; + + bi = kmalloc (sizeof (*bi) + n * sizeof (*info), GFP_KERNEL); + if (!bi) + return -ENOMEM; + bi->n_board_info = n; + memcpy(bi->board_info, info, n * sizeof (*info)); + + down(&board_lock); + list_add_tail(&bi->list, &board_list); + up(&board_lock); + return 0; +} +EXPORT_SYMBOL_GPL(spi_register_board_info); + +/* FIXME someone should add support for a __setup("spi", ...) that + * creates board info from kernel command lines + */ + +static void __init_or_module +scan_boardinfo(struct spi_master *master) +{ + struct boardinfo *bi; + struct device *dev = master->cdev.dev; + + down(&board_lock); + list_for_each_entry(bi, &board_list, list) { + struct spi_board_info *chip = bi->board_info; + unsigned n; + + for (n = bi->n_board_info; n > 0; n--, chip++) { + if (chip->bus_num != master->bus_num) + continue; + /* some controllers only have one chip, so they + * might not use chipselects. otherwise, the + * chipselects are numbered 0..max. + */ + if (chip->chip_select >= master->num_chipselect + && master->num_chipselect) { + dev_dbg(dev, "cs%d > max %d\n", + chip->chip_select, + master->num_chipselect); + continue; + } + (void) spi_new_device(master, chip); + } + } + up(&board_lock); +} + +/*-------------------------------------------------------------------------*/ + +static void spi_master_release(struct class_device *cdev) +{ + struct spi_master *master; + + master = container_of(cdev, struct spi_master, cdev); + put_device(master->cdev.dev); + master->cdev.dev = NULL; + kfree(master); +} + +static struct class spi_master_class = { + .name = "spi_master", + .owner = THIS_MODULE, + .release = spi_master_release, +}; + + +/** + * spi_alloc_master - allocate SPI master controller + * @dev: the controller, possibly using the platform_bus + * @size: how much driver-private data to preallocate; a pointer to this + * memory in the class_data field of the returned class_device + * + * This call is used only by SPI master controller drivers, which are the + * only ones directly touching chip registers. It's how they allocate + * an spi_master structure, prior to calling spi_add_master(). + * + * This must be called from context that can sleep. It returns the SPI + * master structure on success, else NULL. + * + * The caller is responsible for assigning the bus number and initializing + * the master's methods before calling spi_add_master(), or else (on error) + * calling class_device_put() to prevent a memory leak. + */ +struct spi_master * __init_or_module +spi_alloc_master(struct device *dev, unsigned size) +{ + struct spi_master *master; + + master = kzalloc(size + sizeof *master, SLAB_KERNEL); + if (!master) + return NULL; + + master->cdev.class = &spi_master_class; + master->cdev.dev = get_device(dev); + class_set_devdata(&master->cdev, &master[1]); + + return master; +} +EXPORT_SYMBOL_GPL(spi_alloc_master); + +/** + * spi_register_master - register SPI master controller + * @master: initialized master, originally from spi_alloc_master() + * + * SPI master controllers connect to their drivers using some non-SPI bus, + * such as the platform bus. The final stage of probe() in that code + * includes calling spi_register_master() to hook up to this SPI bus glue. + * + * SPI controllers use board specific (often SOC specific) bus numbers, + * and board-specific addressing for SPI devices combines those numbers + * with chip select numbers. Since SPI does not directly support dynamic + * device identification, boards need configuration tables telling which + * chip is at which address. + * + * This must be called from context that can sleep. It returns zero on + * success, else a negative error code (dropping the master's refcount). + */ +int __init_or_module +spi_register_master(struct spi_master *master) +{ + static atomic_t dyn_bus_id = ATOMIC_INIT(0); + struct device *dev = master->cdev.dev; + int status = -ENODEV; + int dynamic = 0; + + /* convention: dynamically assigned bus IDs count down from the max */ + if (master->bus_num == 0) { + master->bus_num = atomic_dec_return(&dyn_bus_id); + dynamic = 0; + } + + /* register the device, then userspace will see it. + * registration fails if the bus ID is in use. + */ + snprintf(master->cdev.class_id, sizeof master->cdev.class_id, + "spi%u", master->bus_num); + status = class_device_register(&master->cdev); + if (status < 0) { + class_device_put(&master->cdev); + goto done; + } + dev_dbg(dev, "registered master %s%s\n", master->cdev.class_id, + dynamic ? " (dynamic)" : ""); + + /* populate children from any spi device tables */ + scan_boardinfo(master); + status = 0; +done: + return status; +} +EXPORT_SYMBOL_GPL(spi_register_master); + + +static int __unregister(struct device *dev, void *unused) +{ + /* note: before about 2.6.14-rc1 this would corrupt memory: */ + device_unregister(dev); + return 0; +} + +/** + * spi_unregister_master - unregister SPI master controller + * @master: the master being unregistered + * + * This call is used only by SPI master controller drivers, which are the + * only ones directly touching chip registers. + * + * This must be called from context that can sleep. + */ +void spi_unregister_master(struct spi_master *master) +{ + class_device_unregister(&master->cdev); + (void) device_for_each_child(master->cdev.dev, NULL, __unregister); +} +EXPORT_SYMBOL_GPL(spi_unregister_master); + +/** + * spi_busnum_to_master - look up master associated with bus_num + * @bus_num: the master's bus number + * + * This call may be used with devices that are registered after + * arch init time. It returns a refcounted pointer to the relevant + * spi_master (which the caller must release), or NULL if there is + * no such master registered. + */ +struct spi_master *spi_busnum_to_master(u16 bus_num) +{ + if (bus_num) { + char name[8]; + struct kobject *bus; + + snprintf(name, sizeof name, "spi%u", bus_num); + bus = kset_find_obj(&spi_master_class.subsys.kset, name); + if (bus) + return container_of(bus, struct spi_master, cdev.kobj); + } + return NULL; +} +EXPORT_SYMBOL_GPL(spi_busnum_to_master); + + +/*-------------------------------------------------------------------------*/ + +/** + * spi_sync - blocking/synchronous SPI data transfers + * @spi: device with which data will be exchanged + * @message: describes the data transfers + * + * This call may only be used from a context that may sleep. The sleep + * is non-interruptible, and has no timeout. Low-overhead controller + * drivers may DMA directly into and out of the message buffers. + * + * Note that the SPI device's chip select is active during the message, + * and then is normally disabled between messages. Drivers for some + * frequently-used devices may want to minimize costs of selecting a chip, + * by leaving it selected in anticipation that the next message will go + * to the same chip. (That may increase power usage.) + * + * The return value is a negative error code if the message could not be + * submitted, else zero. When the value is zero, then message->status is + * also defined: it's the completion code for the transfer, either zero + * or a negative error code from the controller driver. + */ +int spi_sync(struct spi_device *spi, struct spi_message *message) +{ + DECLARE_COMPLETION(done); + int status; + + message->complete = (void (*)(void *)) complete; + message->context = &done; + status = spi_async(spi, message); + if (status == 0) + wait_for_completion(&done); + message->context = NULL; + return status; +} +EXPORT_SYMBOL_GPL(spi_sync); + +#define SPI_BUFSIZ (SMP_CACHE_BYTES) + +static u8 *buf; + +/** + * spi_write_then_read - SPI synchronous write followed by read + * @spi: device with which data will be exchanged + * @txbuf: data to be written (need not be dma-safe) + * @n_tx: size of txbuf, in bytes + * @rxbuf: buffer into which data will be read + * @n_rx: size of rxbuf, in bytes (need not be dma-safe) + * + * This performs a half duplex MicroWire style transaction with the + * device, sending txbuf and then reading rxbuf. The return value + * is zero for success, else a negative errno status code. + * + * Parameters to this routine are always copied using a small buffer, + * large transfers should use use spi_{async,sync}() calls with + * dma-safe buffers. + */ +int spi_write_then_read(struct spi_device *spi, + const u8 *txbuf, unsigned n_tx, + u8 *rxbuf, unsigned n_rx) +{ + static DECLARE_MUTEX(lock); + + int status; + struct spi_message message; + struct spi_transfer x[2]; + u8 *local_buf; + + /* Use preallocated DMA-safe buffer. We can't avoid copying here, + * (as a pure convenience thing), but we can keep heap costs + * out of the hot path ... + */ + if ((n_tx + n_rx) > SPI_BUFSIZ) + return -EINVAL; + + /* ... unless someone else is using the pre-allocated buffer */ + if (down_trylock(&lock)) { + local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL); + if (!local_buf) + return -ENOMEM; + } else + local_buf = buf; + + memset(x, 0, sizeof x); + + memcpy(local_buf, txbuf, n_tx); + x[0].tx_buf = local_buf; + x[0].len = n_tx; + + x[1].rx_buf = local_buf + n_tx; + x[1].len = n_rx; + + /* do the i/o */ + message.transfers = x; + message.n_transfer = ARRAY_SIZE(x); + status = spi_sync(spi, &message); + if (status == 0) { + memcpy(rxbuf, x[1].rx_buf, n_rx); + status = message.status; + } + + if (x[0].tx_buf == buf) + up(&lock); + else + kfree(local_buf); + + return status; +} +EXPORT_SYMBOL_GPL(spi_write_then_read); + +/*-------------------------------------------------------------------------*/ + +static int __init spi_init(void) +{ + buf = kmalloc(SPI_BUFSIZ, SLAB_KERNEL); + if (!buf) + return -ENOMEM; + + bus_register(&spi_bus_type); + class_register(&spi_master_class); + return 0; +} +/* board_info is normally registered in arch_initcall(), + * but even essential drivers wait till later + */ +subsys_initcall(spi_init); + diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h new file mode 100644 index 0000000..51a6769 --- /dev/null +++ b/include/linux/spi/spi.h @@ -0,0 +1,542 @@ +/* + * Copyright (C) 2005 David Brownell + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#ifndef __LINUX_SPI_H +#define __LINUX_SPI_H + +/* + * INTERFACES between SPI master drivers and infrastructure + * (There's no SPI slave support for Linux yet...) + * + * A "struct device_driver" for an spi_device uses "spi_bus_type" and + * needs no special API wrappers (much like platform_bus). These drivers + * are bound to devices based on their names (much like platform_bus), + * and are available in dev->driver. + */ +extern struct bus_type spi_bus_type; + +/** + * struct spi_device - Master side proxy for an SPI slave device + * @dev: Driver model representation of the device. + * @master: SPI controller used with the device. + * @max_speed_hz: Maximum clock rate to be used with this chip + * (on this board); may be changed by the device's driver. + * @chip-select: Chipselect, distinguishing chips handled by "master". + * @mode: The spi mode defines how data is clocked out and in. + * This may be changed by the device's driver. + * @bits_per_word: Data transfers involve one or more words; word sizes + * like eight or 12 bits are common. In-memory wordsizes are + * powers of two bytes (e.g. 20 bit samples use 32 bits). + * This may be changed by the device's driver. + * @irq: Negative, or the number passed to request_irq() to receive + * interrupts from this device. + * @controller_state: Controller's runtime state + * @controller_data: Static board-specific definitions for controller, such + * as FIFO initialization parameters; from board_info.controller_data + * + * An spi_device is used to interchange data between an SPI slave + * (usually a discrete chip) and CPU memory. + * + * In "dev", the platform_data is used to hold information about this + * device that's meaningful to the device's protocol driver, but not + * to its controller. One example might be an identifier for a chip + * variant with slightly different functionality. + */ +struct spi_device { + struct device dev; + struct spi_master *master; + u32 max_speed_hz; + u8 chip_select; + u8 mode; +#define SPI_CPHA 0x01 /* clock phase */ +#define SPI_CPOL 0x02 /* clock polarity */ +#define SPI_MODE_0 (0|0) +#define SPI_MODE_1 (0|SPI_CPHA) +#define SPI_MODE_2 (SPI_CPOL|0) +#define SPI_MODE_3 (SPI_CPOL|SPI_CPHA) +#define SPI_CS_HIGH 0x04 /* chipselect active high? */ + u8 bits_per_word; + int irq; + void *controller_state; + const void *controller_data; + const char *modalias; + + // likely need more hooks for more protocol options affecting how + // the controller talks to its chips, like: + // - bit order (default is wordwise msb-first) + // - memory packing (12 bit samples into low bits, others zeroed) + // - priority + // - chipselect delays + // - ... +}; + +static inline struct spi_device *to_spi_device(struct device *dev) +{ + return container_of(dev, struct spi_device, dev); +} + +/* most drivers won't need to care about device refcounting */ +static inline struct spi_device *spi_dev_get(struct spi_device *spi) +{ + return (spi && get_device(&spi->dev)) ? spi : NULL; +} + +static inline void spi_dev_put(struct spi_device *spi) +{ + if (spi) + put_device(&spi->dev); +} + +/* ctldata is for the bus_master driver's runtime state */ +static inline void *spi_get_ctldata(struct spi_device *spi) +{ + return spi->controller_state; +} + +static inline void spi_set_ctldata(struct spi_device *spi, void *state) +{ + spi->controller_state = state; +} + + +struct spi_message; + + +/** + * struct spi_master - interface to SPI master controller + * @cdev: class interface to this driver + * @bus_num: board-specific (and often SOC-specific) identifier for a + * given SPI controller. + * @num_chipselects: chipselects are used to distinguish individual + * SPI slaves, and are numbered from zero to num_chipselects. + * each slave has a chipselect signal, but it's common that not + * every chipselect is connected to a slave. + * @setup: updates the device mode and clocking records used by a + * device's SPI controller; protocol code may call this. + * @transfer: adds a message to the controller's transfer queue. + * @cleanup: frees controller-specific state + * + * Each SPI master controller can communicate with one or more spi_device + * children. These make a small bus, sharing MOSI, MISO and SCK signals + * but not chip select signals. Each device may be configured to use a + * different clock rate, since those shared signals are ignored unless + * the chip is selected. + * + * The driver for an SPI controller manages access to those devices through + * a queue of spi_message transactions, copyin data between CPU memory and + * an SPI slave device). For each such message it queues, it calls the + * message's completion function when the transaction completes. + */ +struct spi_master { + struct class_device cdev; + + /* other than zero (== assign one dynamically), bus_num is fully + * board-specific. usually that simplifies to being SOC-specific. + * example: one SOC has three SPI controllers, numbered 1..3, + * and one board's schematics might show it using SPI-2. software + * would normally use bus_num=2 for that controller. + */ + u16 bus_num; + + /* chipselects will be integral to many controllers; some others + * might use board-specific GPIOs. + */ + u16 num_chipselect; + + /* setup mode and clock, etc (spi driver may call many times) */ + int (*setup)(struct spi_device *spi); + + /* bidirectional bulk transfers + * + * + The transfer() method may not sleep; its main role is + * just to add the message to the queue. + * + For now there's no remove-from-queue operation, or + * any other request management + * + To a given spi_device, message queueing is pure fifo + * + * + The master's main job is to process its message queue, + * selecting a chip then transferring data + * + If there are multiple spi_device children, the i/o queue + * arbitration algorithm is unspecified (round robin, fifo, + * priority, reservations, preemption, etc) + * + * + Chipselect stays active during the entire message + * (unless modified by spi_transfer.cs_change != 0). + * + The message transfers use clock and SPI mode parameters + * previously established by setup() for this device + */ + int (*transfer)(struct spi_device *spi, + struct spi_message *mesg); + + /* called on release() to free memory provided by spi_master */ + void (*cleanup)(const struct spi_device *spi); +}; + +/* the spi driver core manages memory for the spi_master classdev */ +extern struct spi_master * +spi_alloc_master(struct device *host, unsigned size); + +extern int spi_register_master(struct spi_master *master); +extern void spi_unregister_master(struct spi_master *master); + +extern struct spi_master *spi_busnum_to_master(u16 busnum); + +/*---------------------------------------------------------------------------*/ + +/* + * I/O INTERFACE between SPI controller and protocol drivers + * + * Protocol drivers use a queue of spi_messages, each transferring data + * between the controller and memory buffers. + * + * The spi_messages themselves consist of a series of read+write transfer + * segments. Those segments always read the same number of bits as they + * write; but one or the other is easily ignored by passing a null buffer + * pointer. (This is unlike most types of I/O API, because SPI hardware + * is full duplex.) + * + * NOTE: Allocation of spi_transfer and spi_message memory is entirely + * up to the protocol driver, which guarantees the integrity of both (as + * well as the data buffers) for as long as the message is queued. + */ + +/** + * struct spi_transfer - a read/write buffer pair + * @tx_buf: data to be written (dma-safe address), or NULL + * @rx_buf: data to be read (dma-safe address), or NULL + * @tx_dma: DMA address of buffer, if spi_message.is_dma_mapped + * @rx_dma: DMA address of buffer, if spi_message.is_dma_mapped + * @len: size of rx and tx buffers (in bytes) + * @cs_change: affects chipselect after this transfer completes + * @delay_usecs: microseconds to delay after this transfer before + * (optionally) changing the chipselect status, then starting + * the next transfer or completing this spi_message. + * + * SPI transfers always write the same number of bytes as they read. + * Protocol drivers should always provide rx_buf and/or tx_buf. + * In some cases, they may also want to provide DMA addresses for + * the data being transferred; that may reduce overhead, when the + * underlying driver uses dma. + * + * All SPI transfers start with the relevant chipselect active. Drivers + * can change behavior of the chipselect after the transfer finishes + * (including any mandatory delay). The normal behavior is to leave it + * selected, except for the last transfer in a message. Setting cs_change + * allows two additional behavior options: + * + * (i) If the transfer isn't the last one in the message, this flag is + * used to make the chipselect briefly go inactive in the middle of the + * message. Toggling chipselect in this way may be needed to terminate + * a chip command, letting a single spi_message perform all of group of + * chip transactions together. + * + * (ii) When the transfer is the last one in the message, the chip may + * stay selected until the next transfer. This is purely a performance + * hint; the controller driver may need to select a different device + * for the next message. + */ +struct spi_transfer { + /* it's ok if tx_buf == rx_buf (right?) + * for MicroWire, one buffer must be null + * buffers must work with dma_*map_single() calls + */ + const void *tx_buf; + void *rx_buf; + unsigned len; + + dma_addr_t tx_dma; + dma_addr_t rx_dma; + + unsigned cs_change:1; + u16 delay_usecs; +}; + +/** + * struct spi_message - one multi-segment SPI transaction + * @transfers: the segements of the transaction + * @n_transfer: how many segments + * @spi: SPI device to which the transaction is queued + * @is_dma_mapped: if true, the caller provided both dma and cpu virtual + * addresses for each transfer buffer + * @complete: called to report transaction completions + * @context: the argument to complete() when it's called + * @actual_length: how many bytes were transferd + * @status: zero for success, else negative errno + * @queue: for use by whichever driver currently owns the message + * @state: for use by whichever driver currently owns the message + */ +struct spi_message { + struct spi_transfer *transfers; + unsigned n_transfer; + + struct spi_device *spi; + + unsigned is_dma_mapped:1; + + /* REVISIT: we might want a flag affecting the behavior of the + * last transfer ... allowing things like "read 16 bit length L" + * immediately followed by "read L bytes". Basically imposing + * a specific message scheduling algorithm. + * + * Some controller drivers (message-at-a-time queue processing) + * could provide that as their default scheduling algorithm. But + * others (with multi-message pipelines) would need a flag to + * tell them about such special cases. + */ + + /* completion is reported through a callback */ + void FASTCALL((*complete)(void *context)); + void *context; + unsigned actual_length; + int status; + + /* for optional use by whatever driver currently owns the + * spi_message ... between calls to spi_async and then later + * complete(), that's the spi_master controller driver. + */ + struct list_head queue; + void *state; +}; + +/** + * spi_setup -- setup SPI mode and clock rate + * @spi: the device whose settings are being modified + * + * SPI protocol drivers may need to update the transfer mode if the + * device doesn't work with the mode 0 default. They may likewise need + * to update clock rates or word sizes from initial values. This function + * changes those settings, and must be called from a context that can sleep. + */ +static inline int +spi_setup(struct spi_device *spi) +{ + return spi->master->setup(spi); +} + + +/** + * spi_async -- asynchronous SPI transfer + * @spi: device with which data will be exchanged + * @message: describes the data transfers, including completion callback + * + * This call may be used in_irq and other contexts which can't sleep, + * as well as from task contexts which can sleep. + * + * The completion callback is invoked in a context which can't sleep. + * Before that invocation, the value of message->status is undefined. + * When the callback is issued, message->status holds either zero (to + * indicate complete success) or a negative error code. + * + * Note that although all messages to a spi_device are handled in + * FIFO order, messages may go to different devices in other orders. + * Some device might be higher priority, or have various "hard" access + * time requirements, for example. + */ +static inline int +spi_async(struct spi_device *spi, struct spi_message *message) +{ + message->spi = spi; + return spi->master->transfer(spi, message); +} + +/*---------------------------------------------------------------------------*/ + +/* All these synchronous SPI transfer routines are utilities layered + * over the core async transfer primitive. Here, "synchronous" means + * they will sleep uninterruptibly until the async transfer completes. + */ + +extern int spi_sync(struct spi_device *spi, struct spi_message *message); + +/** + * spi_write - SPI synchronous write + * @spi: device to which data will be written + * @buf: data buffer + * @len: data buffer size + * + * This writes the buffer and returns zero or a negative error code. + * Callable only from contexts that can sleep. + */ +static inline int +spi_write(struct spi_device *spi, const u8 *buf, size_t len) +{ + struct spi_transfer t = { + .tx_buf = buf, + .rx_buf = NULL, + .len = len, + .cs_change = 0, + }; + struct spi_message m = { + .transfers = &t, + .n_transfer = 1, + }; + + return spi_sync(spi, &m); +} + +/** + * spi_read - SPI synchronous read + * @spi: device from which data will be read + * @buf: data buffer + * @len: data buffer size + * + * This writes the buffer and returns zero or a negative error code. + * Callable only from contexts that can sleep. + */ +static inline int +spi_read(struct spi_device *spi, u8 *buf, size_t len) +{ + struct spi_transfer t = { + .tx_buf = NULL, + .rx_buf = buf, + .len = len, + .cs_change = 0, + }; + struct spi_message m = { + .transfers = &t, + .n_transfer = 1, + }; + + return spi_sync(spi, &m); +} + +extern int spi_write_then_read(struct spi_device *spi, + const u8 *txbuf, unsigned n_tx, + u8 *rxbuf, unsigned n_rx); + +/** + * spi_w8r8 - SPI synchronous 8 bit write followed by 8 bit read + * @spi: device with which data will be exchanged + * @cmd: command to be written before data is read back + * + * This returns the (unsigned) eight bit number returned by the + * device, or else a negative error code. Callable only from + * contexts that can sleep. + */ +static inline ssize_t spi_w8r8(struct spi_device *spi, u8 cmd) +{ + ssize_t status; + u8 result; + + status = spi_write_then_read(spi, &cmd, 1, &result, 1); + + /* return negative errno or unsigned value */ + return (status < 0) ? status : result; +} + +/** + * spi_w8r16 - SPI synchronous 8 bit write followed by 16 bit read + * @spi: device with which data will be exchanged + * @cmd: command to be written before data is read back + * + * This returns the (unsigned) sixteen bit number returned by the + * device, or else a negative error code. Callable only from + * contexts that can sleep. + * + * The number is returned in wire-order, which is at least sometimes + * big-endian. + */ +static inline ssize_t spi_w8r16(struct spi_device *spi, u8 cmd) +{ + ssize_t status; + u16 result; + + status = spi_write_then_read(spi, &cmd, 1, (u8 *) &result, 2); + + /* return negative errno or unsigned value */ + return (status < 0) ? status : result; +} + +/*---------------------------------------------------------------------------*/ + +/* + * INTERFACE between board init code and SPI infrastructure. + * + * No SPI driver ever sees these SPI device table segments, but + * it's how the SPI core (or adapters that get hotplugged) grows + * the driver model tree. + * + * As a rule, SPI devices can't be probed. Instead, board init code + * provides a table listing the devices which are present, with enough + * information to bind and set up the device's driver. There's basic + * support for nonstatic configurations too; enough to handle adding + * parport adapters, or microcontrollers acting as USB-to-SPI bridges. + */ + +/* board-specific information about each SPI device */ +struct spi_board_info { + /* the device name and module name are coupled, like platform_bus; + * "modalias" is normally the driver name. + * + * platform_data goes to spi_device.dev.platform_data, + * controller_data goes to spi_device.platform_data, + * irq is copied too + */ + char modalias[KOBJ_NAME_LEN]; + const void *platform_data; + const void *controller_data; + int irq; + + /* slower signaling on noisy or low voltage boards */ + u32 max_speed_hz; + + + /* bus_num is board specific and matches the bus_num of some + * spi_master that will probably be registered later. + * + * chip_select reflects how this chip is wired to that master; + * it's less than num_chipselect. + */ + u16 bus_num; + u16 chip_select; + + /* ... may need additional spi_device chip config data here. + * avoid stuff protocol drivers can set; but include stuff + * needed to behave without being bound to a driver: + * - chipselect polarity + * - quirks like clock rate mattering when not selected + */ +}; + +#ifdef CONFIG_SPI +extern int +spi_register_board_info(struct spi_board_info const *info, unsigned n); +#else +/* board init code may ignore whether SPI is configured or not */ +static inline int +spi_register_board_info(struct spi_board_info const *info, unsigned n) + { return 0; } +#endif + + +/* If you're hotplugging an adapter with devices (parport, usb, etc) + * use spi_new_device() to describe each device. You can also call + * spi_unregister_device() to get start making that device vanish, + * but normally that would be handled by spi_unregister_master(). + */ +extern struct spi_device * +spi_new_device(struct spi_master *, struct spi_board_info *); + +static inline void +spi_unregister_device(struct spi_device *spi) +{ + if (spi) + device_unregister(&spi->dev); +} + +#endif /* __LINUX_SPI_H */ |
