Messages in this thread | | | Date | Tue, 28 Nov 2023 11:26:40 +0100 | Subject | Re: [PATCH 07/55] media: imx8-isi: Stop abusing of min_buffers_needed field | From | Benjamin Gaignard <> |
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Le 28/11/2023 à 10:35, Tomasz Figa a écrit : > On Tue, Nov 28, 2023 at 6:31 PM Benjamin Gaignard > <benjamin.gaignard@collabora.com> wrote: >> >> 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 suspect the use of vb2_dma_sg_plane_desc() and > vb2_dma_contig_plane_dma_addr() may be more correlated to whether > there is a DMA involved or not. Usually V4L2 drivers don't really have > to deal with the DMA API explicitly, because the vb2 framework handles > most of the work.
Unfortunately isn't not true either, for example verisilicon driver use these function but doesn't need DMA engine. I haven't found yet a 100% criteria to decide if driver use or not DMA engine so I plan to fix case by case given maintainers remarks.
Regards, Benjamin
> > Best regards, > Tomasz > >> 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@collabora.com> >>>> CC: Laurent Pinchart <laurent.pinchart@ideasonboard.com> >>>> CC: Mauro Carvalho Chehab <mchehab@kernel.org> >>>> CC: Shawn Guo <shawnguo@kernel.org> >>>> CC: Sascha Hauer <s.hauer@pengutronix.de> >>>> CC: Pengutronix Kernel Team <kernel@pengutronix.de> >>>> CC: Fabio Estevam <festevam@gmail.com> >>>> CC: NXP Linux Team <linux-imx@nxp.com> >>>> --- >>>> 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; >>>>
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