Re: [PATCH 02/55] media: test-drivers: Stop abusing of min_buffers_needed field

[Benjamin Gaignard]

Le 27/11/2023 à 18:00, Shuah Khan a écrit :
> On 11/27/23 09:54, Benjamin Gaignard wrote:
> > 'min_buffers_needed' is suppose to be used to indicate the number
> > of buffers needed by DMA engine to start streaming.
> > Obvious test-drivers don't use DMA engine and just want to specify
> > the minimum number of buffers to allocate when calling VIDIOC_REQBUFS.
> > That 'min_reqbufs_allocation' field purpose so use it.
> > While at it rename function parameter.
>
> So how ate the test-drivers currently abusing this field
> and how does this change benefit?

In videobuf2-core.h min_buffers_needed is documemented as:
"the minimum number of buffers needed before @start_streaming can be called.
Used when a DMA engine cannot be started unless at least this number of buffers have been queued into the driver."

Test-drivers don't use DMA engine so they (ab)use of this variable, like Hans said in this RFC:
https://www.spinics.net/lists/linux-media/msg244455.html

The goal of this series is to distinguish the minimum number of buffers to be allocated in VIDIOC_REQBUF
versus the minimum numbers of buffers needed before start streaming.

Regards,
Benjamin

> I don't have objections to this change, I want to understand
> it a bit more. I would like to see more details on why this
> change is needed.

> thanks,
> -- Shuah