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Date: Tue, 28 Jan 2020 13:45:29 +0900 From: Tomasz Figa <tfiga@...omium.org> To: Hans Verkuil <hverkuil@...all.nl> Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, Hans Verkuil <hans.verkuil@...co.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, Kyungmin Park <kyungmin.park@...sung.com>, Marek Szyprowski <m.szyprowski@...sung.com>, Sakari Ailus <sakari.ailus@....fi>, Laurent Pinchart <laurent.pinchart@...asonboard.com>, Pawel Osciak <posciak@...omium.org>, Linux Media Mailing List <linux-media@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [RFC][PATCH 05/15] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT in REQBUFS On Thu, Jan 23, 2020 at 8:08 PM Hans Verkuil <hverkuil@...all.nl> wrote: > > On 1/22/20 4:48 AM, Sergey Senozhatsky wrote: > > On (20/01/22 11:18), Sergey Senozhatsky wrote: > > [..] > >>>> + * - > >>>> + - __u32 > >>>> - ``reserved``\ [1] > >>>> - A place holder for future extensions. Drivers and applications > >>>> - must set the array to zero. > >>>> + must set the array to zero, unless application wants to specify > >>>> + buffer management ``flags``. > >>> > >>> I think support for this flag should be signaled as a V4L2_BUF_CAP capability. > >>> If the capability is not set, then vb2 should set 'flags' to 0 to preserve the > >>> old 'Drivers and applications must set the array to zero' behavior. > >> > >> The patch set adds V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS towards the end of the > >> series, I guess I can shuffle the patches and change the wording here. > > > > Or I can add separate queue flag and V4L2_BUF_CAP: > > > > struct vb2_queue { > > ... > > allow_cache_hints:1 > > + allow_consistency_hints:1 > > ... > > } > > > > and then have CAP_SUPPORTS_CACHE_HINTS/CAP_SUPPORTS_CONSISTENCY_HINTS. > > Don't these two go hand-in-hand? I.e. either neither are supported, or > both are supported? If so, then one queue flag is sufficient. Cache sync hints are already part of the standard UAPI, so I think there isn't any capability bit needed for them. That said, they aren't really tied to non-consistent MMAP buffers. Userspace using USERPTR can also use them. MMAP buffer consistency hint deserves a capability bit indeed. Best regards, Tomasz
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