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-rw-r--r--drivers/media/usb/uvc/uvc_video.c27
1 files changed, 27 insertions, 0 deletions
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index a777b389a66e..e16464606b14 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -127,10 +127,37 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
struct uvc_streaming_control *ctrl)
{
+ static const struct usb_device_id elgato_cam_link_4k = {
+ USB_DEVICE(0x0fd9, 0x0066)
+ };
struct uvc_format *format = NULL;
struct uvc_frame *frame = NULL;
unsigned int i;
+ /*
+ * The response of the Elgato Cam Link 4K is incorrect: The second byte
+ * contains bFormatIndex (instead of being the second byte of bmHint).
+ * The first byte is always zero. The third byte is always 1.
+ *
+ * The UVC 1.5 class specification defines the first five bits in the
+ * bmHint bitfield. The remaining bits are reserved and should be zero.
+ * Therefore a valid bmHint will be less than 32.
+ *
+ * Latest Elgato Cam Link 4K firmware as of 2021-03-23 needs this fix.
+ * MCU: 20.02.19, FPGA: 67
+ */
+ if (usb_match_one_id(stream->dev->intf, &elgato_cam_link_4k) &&
+ ctrl->bmHint > 255) {
+ u8 corrected_format_index = ctrl->bmHint >> 8;
+
+ uvc_dbg(stream->dev, VIDEO,
+ "Correct USB video probe response from {bmHint: 0x%04x, bFormatIndex: %u} to {bmHint: 0x%04x, bFormatIndex: %u}\n",
+ ctrl->bmHint, ctrl->bFormatIndex,
+ 1, corrected_format_index);
+ ctrl->bmHint = 1;
+ ctrl->bFormatIndex = corrected_format_index;
+ }
+
for (i = 0; i < stream->nformats; ++i) {
if (stream->format[i].index == ctrl->bFormatIndex) {
format = &stream->format[i];

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