On 2/19/20 9:59 AM, Sergey Senozhatsky wrote:
> On (20/02/19 09:25), Hans Verkuil wrote:
> [..]
>>> diff --git a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
>>> index bd08e4f77ae4..68185e94b686 100644
>>> --- a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
>>> +++ b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
>>> @@ -121,7 +121,14 @@ than the number requested.
>>> other changes, then set ``count`` to 0, ``memory`` to
>>> ``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
>>> * - __u32
>>> - - ``reserved``\ [7]
>>> + - ``flags``
>>> + - Specifies additional buffer management attributes. Valid only when
>>> + queue reports :ref:`V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS` capability.
>>> + Old drivers and applications must set it to zero.
>>
>> Drop the 'Valid only' sentence. The V4L2_FLAG_MEMORY_NON_CONSISTENT depends
>> on that capability, but other flags added in the future may not.
>
> The whole sentence, right?
Yes, "Valid only ... capability."
>
>> Inside add a reference to the memory flags section created in patch 3.
>
> Sorry. Inside?
Oops: Inside -> Instead
>
> [..]
>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>> index 72efc1c544cd..169a8cf345ed 100644
>>> --- a/include/uapi/linux/videodev2.h
>>> +++ b/include/uapi/linux/videodev2.h
>>> @@ -938,7 +938,10 @@ struct v4l2_requestbuffers {
>>> __u32 type; /* enum v4l2_buf_type */
>>> __u32 memory; /* enum v4l2_memory */
>>> __u32 capabilities;
>>> - __u32 reserved[1];
>>> + union {
>>> + __u32 flags;
>>> + __u32 reserved[1];
>>> + };
>>
>> How about this:
>>
>> __u8 flags;
>> __u8 reserved[3];
>>
>> That avoids the anonymous union and allows some space for future additions.
>
> Hmm. This way old apps, which clear out ->reserved, e.g.
> memset(&x.reserved, 0x00, sizeof(x.reserved)), won't clear
> out x.flags and can accidentally submit some unintended
> garbage. It's not the case with anon union.
Hmm. I need to think about this some more, so leave in the anon union
for now.
Regards,
Hans
>
> -ss
>
