[linux-uvc-devel] [PATCH] uvcvideo: Add quirk for Quanta NL3 laptop camera

[Daniel Drake]

The Quanta NL3 laptop has a UVC camera which the descriptor says
comes from Realtek: https://gist.github.com/dsd/9a6567baa53c747fd306

Probe fails, because the output terminal (ID 3) references a
non-existent source with ID 6. Fixing it to add itself onto the
end of the chain makes the camera work.

Signed-off-by: Daniel Drake <***@endlessm.com>
---
drivers/media/usb/uvc/uvc_driver.c | 36 ++++++++++++++++++++++++++++++++++++
drivers/media/usb/uvc/uvcvideo.h | 1 +
2 files changed, 37 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index cf27006..3cb4be3 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1575,6 +1575,30 @@ static const char *uvc_print_chain(struct uvc_video_chain *chain)
}

/*
+ * This Realtek camera has a broken descriptor. The output terminal
+ * references a non-existent source. The rest of the simple chain is
+ * fine. Fix the OT to chain on to the end.
+ */
+static void uvc_handle_rtl57a7(struct uvc_device *dev)
+{
+ struct uvc_entity *term;
+
+ term = uvc_entity_by_id(dev, 3);
+ if (!term) {
+ uvc_printk(KERN_INFO, "RTL57A7: no entity with id 3\n");
+ return;
+ }
+
+ if (!UVC_ENTITY_IS_OTERM(term)) {
+ uvc_printk(KERN_INFO, "RTL57A7: entity 3 is not OT\n");
+ return;
+ }
+
+ term->baSourceID[0] = 4;
+ uvc_printk(KERN_INFO, "Applied RTL57A7 chain quirk.\n");
+}
+
+/*
* Scan the device for video chains and register video devices.
*
* Chains are scanned starting at their output terminals and walked backwards.
@@ -1584,6 +1608,9 @@ static int uvc_scan_device(struct uvc_device *dev)
struct uvc_video_chain *chain;
struct uvc_entity *term;

+ if (dev->quirks & UVC_QUIRK_RTL57A7)
+ uvc_handle_rtl57a7(dev);
+
list_for_each_entry(term, &dev->entities, list) {
if (!UVC_ENTITY_IS_OTERM(term))
continue;
@@ -2351,6 +2378,15 @@ static struct usb_device_id uvc_ids[] = {
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
+ /* Realtek camera in Quanta NL3 laptop */
+ { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
+ | USB_DEVICE_ID_MATCH_INT_INFO,
+ .idVendor = 0x0bda,
+ .idProduct = 0x57a7,
+ .bInterfaceClass = USB_CLASS_VIDEO,
+ .bInterfaceSubClass = 1,
+ .bInterfaceProtocol = 0,
+ .driver_info = UVC_QUIRK_RTL57A7 },
/* MT6227 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index c63e5b5..710e480 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -152,6 +152,7 @@
#define UVC_QUIRK_RESTRICT_FRAME_RATE 0x00000200
#define UVC_QUIRK_RESTORE_CTRLS_ON_INIT 0x00000400
#define UVC_QUIRK_FORCE_Y8 0x00000800
+#define UVC_QUIRK_RTL57A7 0x00001000

/* Format flags */
#define UVC_FMT_FLAG_COMPRESSED 0x00000001

[Laurent Pinchart]

Hi Daniel,

Thank you for the patch and sorry for the late response.

Post by Daniel Drake
The Quanta NL3 laptop has a UVC camera which the descriptor says
comes from Realtek: https://gist.github.com/dsd/9a6567baa53c747fd306
Probe fails, because the output terminal (ID 3) references a
non-existent source with ID 6. Fixing it to add itself onto the
end of the chain makes the camera work.

I knew a device with broken descriptors would come one day. It actually took
much longer than I expected.

I'm not sure that adding a device-specific quirk is the bast way to handle
this problem, as it wouldn't really scale if other devices expose buggy
descriptors. A more generic way to patch or override descriptors might be
better, with a single quirk and a pointer to a patch function. This would
require refactoring the quirks system to store a structure pointer instead of
a bitfield in the driver_info field.

What's your opinion ?

Post by Daniel Drake
---
drivers/media/usb/uvc/uvc_driver.c | 36 +++++++++++++++++++++++++++++++++++
drivers/media/usb/uvc/uvcvideo.h | 1 +
2 files changed, 37 insertions(+)
diff --git a/drivers/media/usb/uvc/uvc_driver.c
b/drivers/media/usb/uvc/uvc_driver.c index cf27006..3cb4be3 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1575,6 +1575,30 @@ static const char *uvc_print_chain(struct
uvc_video_chain *chain) }
/*
+ * This Realtek camera has a broken descriptor. The output terminal
+ * references a non-existent source. The rest of the simple chain is
+ * fine. Fix the OT to chain on to the end.
+ */
+static void uvc_handle_rtl57a7(struct uvc_device *dev)
+{
+ struct uvc_entity *term;
+
+ term = uvc_entity_by_id(dev, 3);
+ if (!term) {
+ uvc_printk(KERN_INFO, "RTL57A7: no entity with id 3\n");
+ return;
+ }
+
+ if (!UVC_ENTITY_IS_OTERM(term)) {
+ uvc_printk(KERN_INFO, "RTL57A7: entity 3 is not OT\n");
+ return;
+ }
+
+ term->baSourceID[0] = 4;
+ uvc_printk(KERN_INFO, "Applied RTL57A7 chain quirk.\n");
+}
+
+/*
* Scan the device for video chains and register video devices.
*
* Chains are scanned starting at their output terminals and walked
uvc_device *dev) struct uvc_video_chain *chain;
struct uvc_entity *term;
+ if (dev->quirks & UVC_QUIRK_RTL57A7)
+ uvc_handle_rtl57a7(dev);
+
list_for_each_entry(term, &dev->entities, list) {
if (!UVC_ENTITY_IS_OTERM(term))
continue;
@@ -2351,6 +2378,15 @@ static struct usb_device_id uvc_ids[] = {
.bInterfaceSubClass = 1,
.bInterfaceProtocol = 0,
.driver_info = UVC_QUIRK_PROBE_MINMAX },
+ /* Realtek camera in Quanta NL3 laptop */
+ { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
+ | USB_DEVICE_ID_MATCH_INT_INFO,
+ .idVendor = 0x0bda,
+ .idProduct = 0x57a7,
+ .bInterfaceClass = USB_CLASS_VIDEO,
+ .bInterfaceSubClass = 1,
+ .bInterfaceProtocol = 0,
+ .driver_info = UVC_QUIRK_RTL57A7 },
/* MT6227 */
{ .match_flags = USB_DEVICE_ID_MATCH_DEVICE
| USB_DEVICE_ID_MATCH_INT_INFO,
diff --git a/drivers/media/usb/uvc/uvcvideo.h
b/drivers/media/usb/uvc/uvcvideo.h index c63e5b5..710e480 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -152,6 +152,7 @@
#define UVC_QUIRK_RESTRICT_FRAME_RATE 0x00000200
#define UVC_QUIRK_RESTORE_CTRLS_ON_INIT 0x00000400
#define UVC_QUIRK_FORCE_Y8 0x00000800
+#define UVC_QUIRK_RTL57A7 0x00001000
/* Format flags */
#define UVC_FMT_FLAG_COMPRESSED 0x00000001

[Daniel Drake]

Hi Laurent,

On Sat, Apr 4, 2015 at 3:44 PM, Laurent Pinchart

Post by Laurent Pinchart
I'm not sure that adding a device-specific quirk is the bast way to handle
this problem, as it wouldn't really scale if other devices expose buggy
descriptors. A more generic way to patch or override descriptors might be
better, with a single quirk and a pointer to a patch function. This would
require refactoring the quirks system to store a structure pointer instead of
a bitfield in the driver_info field.

I agree, but I don't currently have time to work on a more advanced approach.

I think that's OK for everyone, as I can work with this patch for the
time being, and if nobody else has broken descriptors, there's no
particular rush.

Thanks,
Daniel