Hi, Hans.
>-----Original Message-----
>From: Hans Verkuil <hverkuil@xxxxxxxxx>
>Sent: Thursday, May 30, 2024 7:32 PM
>To: Nas Chung <nas.chung@xxxxxxxxxxxxxxx>; mchehab@xxxxxxxxxx; linux-
>media@xxxxxxxxxxxxxxx; sebastian.fricke@xxxxxxxxxxxxx;
>m.tretter@xxxxxxxxxxxxxx
>Cc: linux-kernel@xxxxxxxxxxxxxxx
>Subject: Re: [PATCH v2] media: uapi: v4l: Change V4L2_TYPE_IS_CAPTURE
>condition
>
>On 28/05/2024 04:04, Nas Chung wrote:
>> Explicitly compare a buffer type only with valid buffer types,
>> to avoid matching the buffer type outside of valid buffer
>> type set.
>>
>> Signed-off-by: Nas Chung <nas.chung@xxxxxxxxxxxxxxx>
>> ---
>> include/uapi/linux/videodev2.h | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/uapi/linux/videodev2.h
>b/include/uapi/linux/videodev2.h
>> index fe6b67e83751..fa2b7086e480 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -157,6 +157,10 @@ enum v4l2_buf_type {
>> V4L2_BUF_TYPE_PRIVATE = 0x80,
>> };
>>
>> +#define V4L2_TYPE_IS_VALID(type) \
>> + ((type) >= V4L2_BUF_TYPE_VIDEO_CAPTURE \
>> + && (type) <= V4L2_BUF_TYPE_META_OUTPUT)
>> +
>> #define V4L2_TYPE_IS_MULTIPLANAR(type) \
>> ((type) == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE \
>> || (type) == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE)
>> @@ -171,7 +175,8 @@ enum v4l2_buf_type {
>> || (type) == V4L2_BUF_TYPE_SDR_OUTPUT \
>> || (type) == V4L2_BUF_TYPE_META_OUTPUT)
>>
>> -#define V4L2_TYPE_IS_CAPTURE(type) (!V4L2_TYPE_IS_OUTPUT(type))
>> +#define V4L2_TYPE_IS_CAPTURE(type) \
>> + (V4L2_TYPE_IS_VALID(type) && !V4L2_TYPE_IS_OUTPUT(type))
>>
>> enum v4l2_tuner_type {
>> V4L2_TUNER_RADIO = 1,
>
>This patch introduced this warning:
>
>In function 'find_format_by_index',
> inlined from 'vdec_enum_fmt' at
>drivers/media/platform/qcom/venus/vdec.c:452:8:
>drivers/media/platform/qcom/venus/vdec.c:172:32: warning: 'valid' may be
>used uninitialized [-Wmaybe-uninitialized]
> 172 | if (k == index && valid)
> | ~~~~~~~~~~~^~~~~~~~
>drivers/media/platform/qcom/venus/vdec.c: In function 'vdec_enum_fmt':
>drivers/media/platform/qcom/venus/vdec.c:157:22: note: 'valid' was
>declared here
> 157 | bool valid;
> | ^~~~~
>
>This driver does this:
>
> bool valid;
>
> if (V4L2_TYPE_IS_OUTPUT(type)) {
> valid = venus_helper_check_codec(inst, fmt[i].pixfmt);
> } else if (V4L2_TYPE_IS_CAPTURE(type)) {
> valid = venus_helper_check_format(inst, fmt[i].pixfmt);
>
>With your patch both V4L2_TYPE_IS_OUTPUT(type) and
>V4L2_TYPE_IS_CAPTURE(type)
>can return false, something that wasn't possible without this patch.
>
>In this driver the fix would just be to drop the second 'if' altogether,
>so just
>'} else {'.
>
>Since these defines are part of the public API, this change introduces a
>subtle
>behavior difference that can affect applications.
Thank you for a detailed description.
>
>That said, I do consider this an improvement.
>
>I would like some changes, though:
>
>1) Just after "V4L2_BUF_TYPE_META_OUTPUT = 14," in enum
>v4l2_buf_type,
> add a comment saying that V4L2_TYPE_IS_VALID and (for output types)
> V4L2_TYPE_IS_OUTPUT must be updated if a new type is added. It's all
> too easy to forget that otherwise.
>2) Add a patch fixing the venus/vdec.c code.
1), 2) I will address both in v3.
>3) Something else I noticed, but I think this change should be in a
>separate patch:
> V4L2_TYPE_IS_OUTPUT() returns true for V4L2_BUF_TYPE_VIDEO_OVERLAY, but
>that
> definitely belongs to CAPTURE. Nobody really uses that type anymore,
>but still,
> it should be fixed.
3) Would you prefer this modification to be included as a separate patch
in the v3 of this patch series, or should it be submitted as a new
standalone patch ?
Thanks.
Nas.
>
>Regards,
>
> Hans
