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[PATCH v2] HID: autoload hid-multitouch as needed

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From: Benjamin Tissoires <benjamin.tissoires@xxxxxxx>

When the generic hid parsing of the report descriptors in hid-core
detects that the device contains the field ContactID, the device should
be handled by hid-multitouch, and hid-core should release it.
This patch implements a temporary fix for hid-core to automatically
call the loading of hid-multitouch. A better solution would involve
userspace.

The code is inspired from what is done in the bttv module.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxx>
---

Hi guys,

I finally managed to find some time to resend this patch.

Cheers,
Benjamin

 drivers/hid/hid-core.c |   33 ++++++++++++++++++++++++++++++++-
 include/linux/hid.h    |    8 ++++++++
 2 files changed, 40 insertions(+), 1 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 990fe19..a84221e 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1210,6 +1210,31 @@ static struct bin_attribute dev_bin_attr_report_desc = {
 	.size = HID_MAX_DESCRIPTOR_SIZE,
 };
 
+#if defined(CONFIG_MODULES) && defined(MODULE)
+/* Loading of hid_multitouch. This is done from the kernel until we come up
+ * with a more robust solution. */
+static void hid_request_hid_mt_module_async(struct work_struct *work)
+{
+	request_module("hid-multitouch");
+}
+
+static void hid_request_hid_mt_module(struct hid_device *dev)
+{
+	dev->request_hid_mt_module = 1;
+	INIT_WORK(&dev->request_hid_mt_module_wk,
+		hid_request_hid_mt_module_async);
+	schedule_work(&dev->request_hid_mt_module_wk);
+}
+
+static void hid_flush_request_modules(struct hid_device *dev)
+{
+	flush_work_sync(&dev->request_hid_mt_module_wk);
+}
+#else
+#define hid_request_hid_mt_module(dev)
+#define hid_flush_request_modules(dev)
+#endif /* CONFIG_MODULES */
+
 int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
 {
 	static const char *types[] = { "Device", "Pointer", "Mouse", "Device",
@@ -1235,7 +1260,9 @@ int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
 				connect_mask & HID_CONNECT_HIDINPUT_FORCE))
 		hdev->claimed |= HID_CLAIMED_INPUT;
 	if (hdev->quirks & HID_QUIRK_MULTITOUCH) {
-		/* this device should be handled by hid-multitouch, skip it */
+		/* this device should be handled by hid-multitouch, request
+		 * for hid-multitouch to be loaded and leave the device to it */
+		hid_request_hid_mt_module(hdev);
 		return -ENODEV;
 	}
 
@@ -2107,6 +2134,8 @@ struct hid_device *hid_allocate_device(void)
 	INIT_LIST_HEAD(&hdev->debug_list);
 	sema_init(&hdev->driver_lock, 1);
 
+	hdev->request_hid_mt_module = 0;
+
 	return hdev;
 err:
 	put_device(&hdev->dev);
@@ -2121,6 +2150,8 @@ static void hid_remove_device(struct hid_device *hdev)
 		hid_debug_unregister(hdev);
 		hdev->status &= ~HID_STAT_ADDED;
 	}
+	if (hdev->request_hid_mt_module)
+		hid_flush_request_modules(hdev);
 }
 
 /**
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 3a95da6..0058ca9 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -538,6 +538,14 @@ struct hid_device {							/* device report descriptor */
 	struct dentry *debug_events;
 	struct list_head debug_list;
 	wait_queue_head_t debug_wait;
+
+	/* This is a temporary fix to make hid-multitouch loadable from
+	 * the kernel before we come up with more robust solution
+	 * (with userspace involvement).
+	 * In case we detect a multitouch device through the parsing of
+	 * hid-core, we request for hid-multitouch to be loaded. */
+	struct work_struct request_hid_mt_module_wk;
+	bool request_hid_mt_module;
 };
 
 static inline void *hid_get_drvdata(struct hid_device *hdev)
-- 
1.7.7.6

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