[PATCH] USB: drivers/usb/storage/libusual

This patch adds a shim driver libusual, which routes devices between
usb-storage and ub according to the common table, based on unusual_devs.h.
The help and example syntax is in Kconfig.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 266 insertions, 0 deletions

diff --git a/drivers/usb/storage/libusual.c b/drivers/usb/storage/libusual.c
new file mode 100644
index 0000000..61f73d8
--- /dev/null
+++ b/drivers/usb/storage/libusual.c
@@ -0,0 +1,266 @@
+/*
+ * libusual
+ *
+ * The libusual contains the table of devices common for ub and usb-storage.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb_usual.h>
+#include <linux/vmalloc.h>
+
+/*
+ */
+#define USU_MOD_FL_THREAD   1	/* Thread is running */
+#define USU_MOD_FL_PRESENT  2	/* The module is loaded */
+
+struct mod_status {
+	unsigned long fls;
+};
+
+static struct mod_status stat[3];
+static DEFINE_SPINLOCK(usu_lock);
+
+/*
+ */
+#define USB_US_DEFAULT_BIAS	USB_US_TYPE_STOR
+
+#define BIAS_NAME_SIZE  (sizeof("usb-storage"))
+static char bias[BIAS_NAME_SIZE];
+static int usb_usual_bias;
+static const char *bias_names[3] = { "none", "usb-storage", "ub" };
+
+static DECLARE_MUTEX_LOCKED(usu_init_notify);
+static DECLARE_COMPLETION(usu_end_notify);
+static atomic_t total_threads = ATOMIC_INIT(0);
+
+static int usu_probe_thread(void *arg);
+static int parse_bias(const char *bias_s);
+
+/*
+ * The table.
+ */
+#define UNUSUAL_DEV(id_vendor, id_product, bcdDeviceMin, bcdDeviceMax, \
+		    vendorName, productName,useProtocol, useTransport, \
+		    initFunction, flags) \
+{ USB_DEVICE_VER(id_vendor, id_product, bcdDeviceMin,bcdDeviceMax), \
+  .driver_info = (flags)|(USB_US_TYPE_STOR<<24) }
+
+#define USUAL_DEV(useProto, useTrans, useType) \
+{ USB_INTERFACE_INFO(USB_CLASS_MASS_STORAGE, useProto, useTrans), \
+  .driver_info = ((useType)<<24) }
+
+struct usb_device_id storage_usb_ids [] = {
+#	include "unusual_devs.h"
+	{ } /* Terminating entry */
+};
+
+#undef USUAL_DEV
+#undef UNUSUAL_DEV
+
+MODULE_DEVICE_TABLE(usb, storage_usb_ids);
+EXPORT_SYMBOL_GPL(storage_usb_ids);
+
+/*
+ * @type: the module type as an integer
+ */
+void usb_usual_set_present(int type)
+{
+	struct mod_status *st;
+	unsigned long flags;
+
+	if (type <= 0 || type >= 3)
+		return;
+	st = &stat[type];
+	spin_lock_irqsave(&usu_lock, flags);
+	st->fls |= USU_MOD_FL_PRESENT;
+	spin_unlock_irqrestore(&usu_lock, flags);
+}
+EXPORT_SYMBOL_GPL(usb_usual_set_present);
+
+void usb_usual_clear_present(int type)
+{
+	struct mod_status *st;
+	unsigned long flags;
+
+	if (type <= 0 || type >= 3)
+		return;
+	st = &stat[type];
+	spin_lock_irqsave(&usu_lock, flags);
+	st->fls &= ~USU_MOD_FL_PRESENT;
+	spin_unlock_irqrestore(&usu_lock, flags);
+}
+EXPORT_SYMBOL_GPL(usb_usual_clear_present);
+
+/*
+ * Match the calling driver type against the table.
+ * Returns: 0 if the device matches.
+ */
+int usb_usual_check_type(const struct usb_device_id *id, int caller_type)
+{
+	int id_type = USB_US_TYPE(id->driver_info);
+
+	if (caller_type <= 0 || caller_type >= 3)
+		return -EINVAL;
+
+	/* Drivers grab fixed assignment devices */
+	if (id_type == caller_type)
+		return 0;
+	/* Drivers grab devices biased to them */
+	if (id_type == USB_US_TYPE_NONE && caller_type == usb_usual_bias)
+		return 0;
+	return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(usb_usual_check_type);
+
+/*
+ */
+static int usu_probe(struct usb_interface *intf,
+			 const struct usb_device_id *id)
+{
+	int type;
+	int rc;
+	unsigned long flags;
+
+	type = USB_US_TYPE(id->driver_info);
+	if (type == 0)
+		type = usb_usual_bias;
+
+	spin_lock_irqsave(&usu_lock, flags);
+	if ((stat[type].fls & (USU_MOD_FL_THREAD|USU_MOD_FL_PRESENT)) != 0) {
+		spin_unlock_irqrestore(&usu_lock, flags);
+		return -ENXIO;
+	}
+	stat[type].fls |= USU_MOD_FL_THREAD;
+	spin_unlock_irqrestore(&usu_lock, flags);
+
+	rc = kernel_thread(usu_probe_thread, (void*)type, CLONE_VM);
+	if (rc < 0) {
+		printk(KERN_WARNING "libusual: "
+		    "Unable to start the thread for %s: %d\n",
+		    bias_names[type], rc);
+		spin_lock_irqsave(&usu_lock, flags);
+		stat[type].fls &= ~USU_MOD_FL_THREAD;
+		spin_unlock_irqrestore(&usu_lock, flags);
+		return rc;	/* Not being -ENXIO causes a message printed */
+	}
+	atomic_inc(&total_threads);
+
+	return -ENXIO;
+}
+
+static void usu_disconnect(struct usb_interface *intf)
+{
+	;	/* We should not be here. */
+}
+
+static struct usb_driver usu_driver = {
+	.owner =	THIS_MODULE,
+	.name =		"libusual",
+	.probe =	usu_probe,
+	.disconnect =	usu_disconnect,
+	.id_table =	storage_usb_ids,
+};
+
+/*
+ * A whole new thread for a purpose of request_module seems quite stupid.
+ * The request_module forks once inside again. However, if we attempt
+ * to load a storage module from our own modprobe thread, that module
+ * references our symbols, which cannot be resolved until our module is
+ * initialized. I wish there was a way to wait for the end of initialization.
+ * The module notifier reports MODULE_STATE_COMING only.
+ * So, we wait until module->init ends as the next best thing.
+ */
+static int usu_probe_thread(void *arg)
+{
+	int type = (unsigned long) arg;
+	struct mod_status *st = &stat[type];
+	int rc;
+	unsigned long flags;
+
+	daemonize("libusual_%d", type);	/* "usb-storage" is kinda too long */
+
+	/* A completion does not work here because it's counted. */
+	down(&usu_init_notify);
+	up(&usu_init_notify);
+
+	rc = request_module(bias_names[type]);
+	spin_lock_irqsave(&usu_lock, flags);
+	if (rc == 0 && (st->fls & USU_MOD_FL_PRESENT) == 0) {
+		/*
+		 * This should not happen, but let us keep tabs on it.
+		 */
+		printk(KERN_NOTICE "libusual: "
+		    "modprobe for %s succeeded, but module is not present\n",
+		    bias_names[type]);
+	}
+	st->fls &= ~USU_MOD_FL_THREAD;
+	spin_unlock_irqrestore(&usu_lock, flags);
+
+	complete_and_exit(&usu_end_notify, 0);
+}
+
+/*
+ */
+static int __init usb_usual_init(void)
+{
+	int rc;
+
+	bias[BIAS_NAME_SIZE-1] = 0;
+	usb_usual_bias = parse_bias(bias);
+
+	rc = usb_register(&usu_driver);
+	up(&usu_init_notify);
+	return rc;
+}
+
+static void __exit usb_usual_exit(void)
+{
+	/*
+	 * We do not check for any drivers present, because
+	 * they keep us pinned with symbol references.
+	 */
+
+	usb_deregister(&usu_driver);
+
+	while (atomic_read(&total_threads) > 0) {
+		wait_for_completion(&usu_end_notify);
+		atomic_dec(&total_threads);
+	}
+}
+
+/*
+ * Validate and accept the bias parameter.
+ * Maybe make an sysfs method later. XXX
+ */
+static int parse_bias(const char *bias_s)
+{
+	int i;
+	int bias_n = 0;
+
+	if (bias_s[0] == 0 || bias_s[0] == ' ') {
+		bias_n = USB_US_DEFAULT_BIAS;
+	} else {
+		for (i = 1; i < 3; i++) {
+			if (strcmp(bias_s, bias_names[i]) == 0) {
+				bias_n = i;
+				break;
+			}
+		}
+		if (bias_n == 0) {
+			bias_n = USB_US_DEFAULT_BIAS;
+			printk(KERN_INFO
+			    "libusual: unknown bias \"%s\", using \"%s\"\n",
+			    bias_s, bias_names[bias_n]);
+		}
+	}
+	return bias_n;
+}
+
+module_init(usb_usual_init);
+module_exit(usb_usual_exit);
+
+module_param_string(bias, bias, BIAS_NAME_SIZE,  S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(bias, "Bias to usb-storage or ub");
+
+MODULE_LICENSE("GPL");