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Diffstat (limited to 'Documentation/i2c')
| -rw-r--r-- | Documentation/i2c/porting-clients | 160 |
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diff --git a/Documentation/i2c/porting-clients b/Documentation/i2c/porting-clients deleted file mode 100644 index 7bf82c0..0000000 --- a/Documentation/i2c/porting-clients +++ /dev/null @@ -1,160 +0,0 @@ -Revision 7, 2007-04-19 -Jean Delvare <khali@linux-fr.org> -Greg KH <greg@kroah.com> - -This is a guide on how to convert I2C chip drivers from Linux 2.4 to -Linux 2.6. I have been using existing drivers (lm75, lm78) as examples. -Then I converted a driver myself (lm83) and updated this document. -Note that this guide is strongly oriented towards hardware monitoring -drivers. Many points are still valid for other type of drivers, but -others may be irrelevant. - -There are two sets of points below. The first set concerns technical -changes. The second set concerns coding policy. Both are mandatory. - -Although reading this guide will help you porting drivers, I suggest -you keep an eye on an already ported driver while porting your own -driver. This will help you a lot understanding what this guide -exactly means. Choose the chip driver that is the more similar to -yours for best results. - -Technical changes: - -* [Driver type] Any driver that was relying on i2c-isa has to be - converted to a proper isa, platform or pci driver. This is not - covered by this guide. - -* [Includes] Get rid of "version.h" and <linux/i2c-proc.h>. - Includes typically look like that: - #include <linux/module.h> - #include <linux/init.h> - #include <linux/slab.h> - #include <linux/jiffies.h> - #include <linux/i2c.h> - #include <linux/hwmon.h> /* for hardware monitoring drivers */ - #include <linux/hwmon-sysfs.h> - #include <linux/hwmon-vid.h> /* if you need VRM support */ - #include <linux/err.h> /* for class registration */ - Please respect this inclusion order. Some extra headers may be - required for a given driver (e.g. "lm75.h"). - -* [Addresses] SENSORS_I2C_END becomes I2C_CLIENT_END, ISA addresses - are no more handled by the i2c core. Address ranges are no more - supported either, define each individual address separately. - SENSORS_INSMOD_<n> becomes I2C_CLIENT_INSMOD_<n>. - -* [Client data] Get rid of sysctl_id. Try using standard names for - register values (for example, temp_os becomes temp_max). You're - still relatively free here, but you *have* to follow the standard - names for sysfs files (see the Sysctl section below). - -* [Function prototypes] The detect functions loses its flags - parameter. Sysctl (e.g. lm75_temp) and miscellaneous functions - are off the list of prototypes. This usually leaves five - prototypes: - static int lm75_attach_adapter(struct i2c_adapter *adapter); - static int lm75_detect(struct i2c_adapter *adapter, int address, - int kind); - static void lm75_init_client(struct i2c_client *client); - static int lm75_detach_client(struct i2c_client *client); - static struct lm75_data lm75_update_device(struct device *dev); - -* [Sysctl] All sysctl stuff is of course gone (defines, ctl_table - and functions). Instead, you have to define show and set functions for - each sysfs file. Only define set for writable values. Take a look at an - existing 2.6 driver for details (it87 for example). Don't forget - to define the attributes for each file (this is that step that - links callback functions). Use the file names specified in - Documentation/hwmon/sysfs-interface for the individual files. Also - convert the units these files read and write to the specified ones. - If you need to add a new type of file, please discuss it on the - sensors mailing list <lm-sensors@lm-sensors.org> by providing a - patch to the Documentation/hwmon/sysfs-interface file. - -* [Attach] The attach function should make sure that the adapter's - class has I2C_CLASS_HWMON (or whatever class is suitable for your - driver), using the following construct: - if (!(adapter->class & I2C_CLASS_HWMON)) - return 0; - Call i2c_probe() instead of i2c_detect(). - -* [Detect] As mentioned earlier, the flags parameter is gone. - The type_name and client_name strings are replaced by a single - name string, which will be filled with a lowercase, short string. - The labels used for error paths are reduced to the number needed. - It is advised that the labels are given descriptive names such as - exit and exit_free. Don't forget to properly set err before - jumping to error labels. By the way, labels should be left-aligned. - Use kzalloc instead of kmalloc. - Use i2c_set_clientdata to set the client data (as opposed to - a direct access to client->data). - Use strlcpy instead of strcpy or snprintf to copy the client name. - Replace the sysctl directory registration by calls to - device_create_file. Move the driver initialization before any - sysfs file creation. - Register the client with the hwmon class (using hwmon_device_register) - if applicable. - Drop client->id. - Drop any 24RF08 corruption prevention you find, as this is now done - at the i2c-core level, and doing it twice voids it. - Don't add I2C_CLIENT_ALLOW_USE to client->flags, it's the default now. - -* [Init] Limits must not be set by the driver (can be done later in - user-space). Chip should not be reset default (although a module - parameter may be used to force it), and initialization should be - limited to the strictly necessary steps. - -* [Detach] Remove the call to i2c_deregister_entry. Do not log an - error message if i2c_detach_client fails, as i2c-core will now do - it for you. - Unregister from the hwmon class if applicable. - -* [Update] The function prototype changed, it is now - passed a device structure, which you have to convert to a client - using to_i2c_client(dev). The update function should return a - pointer to the client data. - Don't access client->data directly, use i2c_get_clientdata(client) - instead. - Use time_after() instead of direct jiffies comparison. - -* [Interface] Make sure there is a MODULE_LICENSE() line, at the bottom - of the file (after MODULE_AUTHOR() and MODULE_DESCRIPTION(), in this - order). - -* [Driver] The flags field of the i2c_driver structure is gone. - I2C_DF_NOTIFY is now the default behavior. - The i2c_driver structure has a driver member, which is itself a - structure, those name member should be initialized to a driver name - string. i2c_driver itself has no name member anymore. - -* [Driver model] Instead of shutdown or reboot notifiers, provide a - shutdown() method in your driver. - -* [Power management] Use the driver model suspend() and resume() - callbacks instead of the obsolete pm_register() calls. - -Coding policy: - -* [Copyright] Use (C), not (c), for copyright. - -* [Debug/log] Get rid of #ifdef DEBUG/#endif constructs whenever you - can. Calls to printk for debugging purposes are replaced by calls to - dev_dbg where possible, else to pr_debug. Here is an example of how - to call it (taken from lm75_detect): - dev_dbg(&client->dev, "Starting lm75 update\n"); - Replace other printk calls with the dev_info, dev_err or dev_warn - function, as appropriate. - -* [Constants] Constants defines (registers, conversions) should be - aligned. This greatly improves readability. - Alignments are achieved by the means of tabs, not spaces. Remember - that tabs are set to 8 in the Linux kernel code. - -* [Layout] Avoid extra empty lines between comments and what they - comment. Respect the coding style (see Documentation/CodingStyle), - in particular when it comes to placing curly braces. - -* [Comments] Make sure that no comment refers to a file that isn't - part of the Linux source tree (typically doc/chips/<chip name>), - and that remaining comments still match the code. Merging comment - lines when possible is encouraged. |
