On Tue, Nov 28, 2023 at 06:35:51PM +0900, Tomasz Figa wrote: > On Tue, Nov 28, 2023 at 6:31 PM Benjamin Gaignard 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. And this is anyway not related to DMA at all, but to the logic each driver implements when it deals with buffers. There's a lower chance a USB driver driver will have a hard requirement for more than one buffer compared to an AMBA/platform/PCI device driver, but at the end of the day, each driver needs to be analyzed individually to check what they require. Benjamin, I think you'll have some more homework to do :-) > > 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. > > > > >> 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; > > >> -- Regards, Laurent Pinchart
