2 files changed, 50 insertions, 11 deletions

diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 154f5bd45940..049d664e94f0 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -866,8 +866,8 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input)
 {
 	struct uvc_fh *handle = fh;
 	struct uvc_video_chain *chain = handle->chain;
+	u8 *buf;
 	int ret;
-	u8 i;
 
 	if (chain->selector == NULL ||
 	    (chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
@@ -875,22 +875,27 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input)
 		return 0;
 	}
 
+	buf = kmalloc(1, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
 	ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, chain->selector->id,
 			     chain->dev->intfnum,  UVC_SU_INPUT_SELECT_CONTROL,
-			     &i, 1);
-	if (ret < 0)
-		return ret;
+			     buf, 1);
+	if (!ret)
+		*input = *buf - 1;
 
-	*input = i - 1;
-	return 0;
+	kfree(buf);
+
+	return ret;
 }
 
 static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input)
 {
 	struct uvc_fh *handle = fh;
 	struct uvc_video_chain *chain = handle->chain;
+	u8 *buf;
 	int ret;
-	u32 i;
 
 	ret = uvc_acquire_privileges(handle);
 	if (ret < 0)
@@ -906,10 +911,17 @@ static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input)
 	if (input >= chain->selector->bNrInPins)
 		return -EINVAL;
 
-	i = input + 1;
-	return uvc_query_ctrl(chain->dev, UVC_SET_CUR, chain->selector->id,
-			      chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
-			      &i, 1);
+	buf = kmalloc(1, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	*buf = input + 1;
+	ret = uvc_query_ctrl(chain->dev, UVC_SET_CUR, chain->selector->id,
+			     chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
+			     buf, 1);
+	kfree(buf);
+
+	return ret;
 }
 
 static int uvc_ioctl_queryctrl(struct file *file, void *fh,
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index a550dbe36dc5..3fae3bfb2bdd 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -89,10 +89,37 @@ 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];