Hi Laurent
On Sat, 6 May 2023 at 09:14, Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
>
> The intervals pointer is incremented for each interval when parsing the
> format descriptor. This doesn't cause any issue as such, but gets in the
> way of constifying some pointers. Modify the parsing code to index the
> intervals pointer as an array and increment it in one go at end of
> parsing.
>
> Careful readers will notice that the maxIntervalIndex variable is set to
> 1 instead of n - 2 when bFrameIntervalType has a zero value. This is
> functionally equivalent, as n is equal to 3 in that case.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Reviewed-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
> drivers/media/usb/uvc/uvc_driver.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 446bd8ff128c..11e4fa007f3f 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -370,6 +370,8 @@ static int uvc_parse_format(struct uvc_device *dev,
> */
> while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE &&
> buffer[2] == ftype) {
> + unsigned int maxIntervalIndex;
> +
> frame = &format->frames[format->nframes];
> if (ftype != UVC_VS_FRAME_FRAME_BASED)
> n = buflen > 25 ? buffer[25] : 0;
> @@ -418,7 +420,7 @@ static int uvc_parse_format(struct uvc_device *dev,
>
> for (i = 0; i < n; ++i) {
> interval = get_unaligned_le32(&buffer[26+4*i]);
> - *(*intervals)++ = interval ? interval : 1;
> + (*intervals)[i] = interval ? interval : 1;
> }
>
> /*
> @@ -440,11 +442,11 @@ static int uvc_parse_format(struct uvc_device *dev,
> * frame->wWidth * frame->wHeight / 8;
>
> /* Clamp the default frame interval to the boundaries. */
> - n -= frame->bFrameIntervalType ? 1 : 2;
> + maxIntervalIndex = frame->bFrameIntervalType ? n - 1 : 1;
Maybe it is worth mentioning that bFrameIntervalType == 0 is a
continuous interval. idex 0 is min and 1 is max.
> frame->dwDefaultFrameInterval =
> clamp(frame->dwDefaultFrameInterval,
> frame->dwFrameInterval[0],
> - frame->dwFrameInterval[n]);
> + frame->dwFrameInterval[maxIntervalIndex]);
>
> /*
> * Some devices report frame intervals that are not functional.
> @@ -463,6 +465,8 @@ static int uvc_parse_format(struct uvc_device *dev,
> (100000000 / frame->dwDefaultFrameInterval) % 10);
>
> format->nframes++;
> + *intervals += n;
> +
> buflen -= buffer[0];
> buffer += buffer[0];
> }
> --
> Regards,
>
> Laurent Pinchart
>
--
Ricardo Ribalda
