Re: [PATCH 07/55] media: imx8-isi: Stop abusing of min_buffers_needed field

[Benjamin Gaignard]

Le 27/11/2023 à 18:07, Laurent Pinchart a écrit :
> Hi Benjamin,
>
> Thank you for the patch.
>
> On Mon, Nov 27, 2023 at 05:54:06PM +0100, Benjamin Gaignard wrote:
> > 'min_buffers_needed' is suppose to be used to indicate the number
> > of buffers needed by DMA engine to start streaming.
> > imx8-isi driver doesn't use DMA engine and just want to specify
> What do you mean, "doesn't use DMA engine" ? The ISI surely has DMA
> engines :-)

I have done assumption on drivers given if they use or dma_* functions.
I have considers that all PCI drivers are using DMA engine and
I don't know the design for each drivers so I hope to get this information
from maintainers and fix that in v2.
If imx8-isi driver needs a minimum number of buffers before start streaming
I will do a v2 and use min_dma_buffers_needed instead.

Regards,
Benjamin

> > the minimum number of buffers to allocate when calling VIDIOC_REQBUFS.
> > That 'min_reqbufs_allocation' field purpose so use it.
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> > CC: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > CC: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> > CC: Shawn Guo <shawnguo@xxxxxxxxxx>
> > CC: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> > CC: Pengutronix Kernel Team <kernel@xxxxxxxxxxxxxx>
> > CC: Fabio Estevam <festevam@xxxxxxxxx>
> > CC: NXP Linux Team <linux-imx@xxxxxxx>
> > ---
> >   drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
> > index 49bca2b01cc6..81673ff9084b 100644
> > --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
> > +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
> > @@ -1453,7 +1453,7 @@ int mxc_isi_video_register(struct mxc_isi_pipe *pipe,
> >   	q->mem_ops = &vb2_dma_contig_memops;
> >   	q->buf_struct_size = sizeof(struct mxc_isi_buffer);
> >   	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> > -	q->min_buffers_needed = 2;
> > +	q->min_reqbufs_allocation = 2;
> >   	q->lock = &video->lock;
> >   	q->dev = pipe->isi->dev;
> >