HID: Add device group to modalias

HID devices are only partially presented to userland.  Hotplugged
devices emit events containing a modalias based on the basic bus,
vendor and product entities. However, in practise a hid device can
depend on details such as a single usb interface or a particular item
in a report descriptor.

This patch adds a device group to the hid device id, and broadcasts it
using uevent and the device modalias.  The module alias generation is
modified to match. As a consequence, a device with a non-zero group
will be processed by the corresponding group driver instead of by the
generic hid driver.
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Acked-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-core.c

@@ -1222,6 +1222,7 @@ static bool hid_match_one_id(struct hid_device *hdev,
 		const struct hid_device_id *id)
 {
 	return id->bus == hdev->bus &&
+		(id->group == HID_GROUP_ANY || id->group == hdev->group) &&
 		(id->vendor == HID_ANY_ID || id->vendor == hdev->vendor) &&
 		(id->product == HID_ANY_ID || id->product == hdev->product);
 }
@@ -1694,6 +1695,7 @@ static ssize_t store_new_id(struct device_driver *drv, const char *buf,
 		return -ENOMEM;
 
 	dynid->id.bus = bus;
+	dynid->id.group = HID_GROUP_ANY;
 	dynid->id.vendor = vendor;
 	dynid->id.product = product;
 	dynid->id.driver_data = driver_data;
@@ -1817,6 +1819,23 @@ static int hid_device_remove(struct device *dev)
 	return 0;
 }
 
+static ssize_t modalias_show(struct device *dev, struct device_attribute *a,
+			     char *buf)
+{
+	struct hid_device *hdev = container_of(dev, struct hid_device, dev);
+	int len;
+
+	len = snprintf(buf, PAGE_SIZE, "hid:b%04Xg%04Xv%08Xp%08X\n",
+		       hdev->bus, hdev->group, hdev->vendor, hdev->product);
+
+	return (len >= PAGE_SIZE) ? (PAGE_SIZE - 1) : len;
+}
+
+static struct device_attribute hid_dev_attrs[] = {
+	__ATTR_RO(modalias),
+	__ATTR_NULL,
+};
+
 static int hid_uevent(struct device *dev, struct kobj_uevent_env *env)
 {
 	struct hid_device *hdev = container_of(dev, struct hid_device, dev);
@@ -1834,8 +1853,8 @@ static int hid_uevent(struct device *dev, struct kobj_uevent_env *env)
 	if (add_uevent_var(env, "HID_UNIQ=%s", hdev->uniq))
 		return -ENOMEM;
 
-	if (add_uevent_var(env, "MODALIAS=hid:b%04Xv%08Xp%08X",
-			hdev->bus, hdev->vendor, hdev->product))
+	if (add_uevent_var(env, "MODALIAS=hid:b%04Xg%04Xv%08Xp%08X",
+			   hdev->bus, hdev->group, hdev->vendor, hdev->product))
 		return -ENOMEM;
 
 	return 0;
@@ -1843,6 +1862,7 @@ static int hid_uevent(struct device *dev, struct kobj_uevent_env *env)
 
 static struct bus_type hid_bus_type = {
 	.name		= "hid",
+	.dev_attrs	= hid_dev_attrs,
 	.match		= hid_bus_match,
 	.probe		= hid_device_probe,
 	.remove		= hid_device_remove,

include/linux/hid.h

@@ -476,6 +476,7 @@ struct hid_device {							/* device report descriptor */
 	unsigned maxcollection;						/* Number of parsed collections */
 	unsigned maxapplication;					/* Number of applications */
 	__u16 bus;							/* BUS ID */
+	__u16 group;							/* Report group */
 	__u32 vendor;							/* Vendor ID */
 	__u32 product;							/* Product ID */
 	__u32 version;							/* HID version */

include/linux/mod_devicetable.h

@@ -132,10 +132,11 @@ struct usb_device_id {
 #define USB_DEVICE_ID_MATCH_INT_PROTOCOL	0x0200
 
 #define HID_ANY_ID				(~0)
+#define HID_GROUP_ANY				0x0000
 
 struct hid_device_id {
 	__u16 bus;
-	__u16 pad1;
+	__u16 group;
 	__u32 vendor;
 	__u32 product;
 	kernel_ulong_t driver_data

scripts/mod/file2alias.c

@@ -336,10 +336,12 @@ static int do_hid_entry(const char *filename,
 			     struct hid_device_id *id, char *alias)
 {
 	id->bus = TO_NATIVE(id->bus);
+	id->group = TO_NATIVE(id->group);
 	id->vendor = TO_NATIVE(id->vendor);
 	id->product = TO_NATIVE(id->product);
 
 	sprintf(alias, "hid:b%04X", id->bus);
+	ADD(alias, "g", id->group != HID_GROUP_ANY, id->group);
 	ADD(alias, "v", id->vendor != HID_ANY_ID, id->vendor);
 	ADD(alias, "p", id->product != HID_ANY_ID, id->product);