Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751217AbdIKLDr (ORCPT ); Mon, 11 Sep 2017 07:03:47 -0400 Received: from lb3-smtp-cloud7.xs4all.net ([194.109.24.31]:48597 "EHLO lb3-smtp-cloud7.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750986AbdIKLDq (ORCPT ); Mon, 11 Sep 2017 07:03:46 -0400 Subject: Re: [PATCH v3 02/15] [media] vb2: add explicit fence user API From: Hans Verkuil To: Gustavo Padovan , linux-media@vger.kernel.org Cc: Mauro Carvalho Chehab , Shuah Khan , linux-kernel@vger.kernel.org, Gustavo Padovan References: <20170907184226.27482-1-gustavo@padovan.org> <20170907184226.27482-3-gustavo@padovan.org> Message-ID: <0a601353-522d-6534-7068-23ef8766046c@xs4all.nl> Date: Mon, 11 Sep 2017 13:03:41 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4wfMLhRxSyNxvx8q1hRs+pqT81NHvZY4qbKAtWIRPXlxk7f43eZlQlf8KY959C4aExizXYFm3yj9BYXFI096vcT+RmN+zTwF4NSg7ToT8ZQisCdfTtQNAo +u3/oU0gJ/WrQeuKxS9DNWZ+vIja8x1PGWDPH7gbskdE714GcDv8fXqwFd7LGXUibireRgyxx8P/whWWLEGVpFJ/rTnXF9KGhGDchf3keXXrE5jIPvMEtYI5 d9fQnxm8DlExG25yf/8s3Hi8afKcc6jZheQP4qgvYe3VPKcG+63UFR8gC35tdGHT81+dcfcpasgjSR3va17Q6Q== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5930 Lines: 150 On 09/11/2017 12:55 PM, Hans Verkuil wrote: > On 09/07/2017 08:42 PM, Gustavo Padovan wrote: >> From: Gustavo Padovan >> >> Turn the reserved2 field into fence_fd that we will use to send >> an in-fence to the kernel and return an out-fence from the kernel to >> userspace. >> >> Two new flags were added, V4L2_BUF_FLAG_IN_FENCE, that should be used >> when sending a fence to the kernel to be waited on, and >> V4L2_BUF_FLAG_OUT_FENCE, to ask the kernel to give back an out-fence. >> >> v2: add documentation >> >> Signed-off-by: Gustavo Padovan >> --- >> Documentation/media/uapi/v4l/buffer.rst | 19 +++++++++++++++++++ >> drivers/media/usb/cpia2/cpia2_v4l.c | 2 +- >> drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 4 ++-- >> drivers/media/v4l2-core/videobuf2-v4l2.c | 2 +- >> include/uapi/linux/videodev2.h | 4 +++- >> 5 files changed, 26 insertions(+), 5 deletions(-) >> >> diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst >> index ae6ee73f151c..664507ad06c6 100644 >> --- a/Documentation/media/uapi/v4l/buffer.rst >> +++ b/Documentation/media/uapi/v4l/buffer.rst >> @@ -648,6 +648,25 @@ Buffer Flags >> - Start Of Exposure. The buffer timestamp has been taken when the >> exposure of the frame has begun. This is only valid for the >> ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` buffer type. >> + * .. _`V4L2-BUF-FLAG-IN-FENCE`: >> + >> + - ``V4L2_BUF_FLAG_IN_FENCE`` >> + - 0x00200000 >> + - Ask V4L2 to wait on fence passed in ``fence_fd`` field. The buffer >> + won't be queued to the driver until the fence signals. >> + >> + * .. _`V4L2-BUF-FLAG-OUT-FENCE`: >> + >> + - ``V4L2_BUF_FLAG_OUT_FENCE`` >> + - 0x00400000 >> + - Request a fence for the next buffer to be queued to V4L2 driver. >> + The fence received back through the ``fence_fd`` field doesn't >> + necessarily relate to the current buffer in the >> + :ref:`VIDIOC_QBUF ` ioctl. Although, most of the time >> + the fence will relate to the current buffer it can't be guaranteed. >> + So to tell userspace which buffer is associated to the out_fence, >> + one should listen for the ``V4L2_EVENT_BUF_QUEUED`` event that >> + provide the id of the buffer when it is queued to the V4L2 driver. > > As mentioned in the previous patch, this flag should just signal that userspace > wants to receive a BUF_QUEUED event with the out-fence for this buffer. It's up > to the driver to ensure the correct ordering of the events. I'll wait for v4 before continuing my review. Hans > > I'm missing documentation for the new fence_fd field. > > It should mention that fence_fd is ignored if the IN_FENCE isn't set. Applications > will set fence_fd (aka reserved2) to 0, which should be fine as long as IN_FENCE > isn't set. > >> >> >> >> diff --git a/drivers/media/usb/cpia2/cpia2_v4l.c b/drivers/media/usb/cpia2/cpia2_v4l.c >> index 3dedd83f0b19..6cde686bf44c 100644 >> --- a/drivers/media/usb/cpia2/cpia2_v4l.c >> +++ b/drivers/media/usb/cpia2/cpia2_v4l.c >> @@ -948,7 +948,7 @@ static int cpia2_dqbuf(struct file *file, void *fh, struct v4l2_buffer *buf) >> buf->sequence = cam->buffers[buf->index].seq; >> buf->m.offset = cam->buffers[buf->index].data - cam->frame_buffer; >> buf->length = cam->frame_size; >> - buf->reserved2 = 0; >> + buf->fence_fd = -1; >> buf->reserved = 0; >> memset(&buf->timecode, 0, sizeof(buf->timecode)); >> >> diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c >> index 821f2aa299ae..d624fb5df130 100644 >> --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c >> +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c >> @@ -370,7 +370,7 @@ struct v4l2_buffer32 { >> __s32 fd; >> } m; >> __u32 length; >> - __u32 reserved2; >> + __s32 fence_fd; >> __u32 reserved; >> }; >> >> @@ -533,8 +533,8 @@ static int put_v4l2_buffer32(struct v4l2_buffer *kp, struct v4l2_buffer32 __user >> put_user(kp->timestamp.tv_usec, &up->timestamp.tv_usec) || >> copy_to_user(&up->timecode, &kp->timecode, sizeof(struct v4l2_timecode)) || >> put_user(kp->sequence, &up->sequence) || >> - put_user(kp->reserved2, &up->reserved2) || >> put_user(kp->reserved, &up->reserved) || >> + put_user(kp->fence_fd, &up->fence_fd) || > > Could you move this up one line? It's easier to parse this diff if it is clear > that fence_fd replaced reserved2. > >> put_user(kp->length, &up->length)) >> return -EFAULT; >> >> diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c >> index 0c0669976bdc..110fb45fef6f 100644 >> --- a/drivers/media/v4l2-core/videobuf2-v4l2.c >> +++ b/drivers/media/v4l2-core/videobuf2-v4l2.c >> @@ -203,7 +203,7 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb) >> b->timestamp = ns_to_timeval(vb->timestamp); >> b->timecode = vbuf->timecode; >> b->sequence = vbuf->sequence; >> - b->reserved2 = 0; >> + b->fence_fd = -1; >> b->reserved = 0; >> >> if (q->is_multiplanar) { >> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h >> index 185d6a0acc06..e5abab9a908c 100644 >> --- a/include/uapi/linux/videodev2.h >> +++ b/include/uapi/linux/videodev2.h >> @@ -924,7 +924,7 @@ struct v4l2_buffer { >> __s32 fd; >> } m; >> __u32 length; >> - __u32 reserved2; >> + __s32 fence_fd; >> __u32 reserved; >> }; >> >> @@ -961,6 +961,8 @@ struct v4l2_buffer { >> #define V4L2_BUF_FLAG_TSTAMP_SRC_SOE 0x00010000 >> /* mem2mem encoder/decoder */ >> #define V4L2_BUF_FLAG_LAST 0x00100000 >> +#define V4L2_BUF_FLAG_IN_FENCE 0x00200000 >> +#define V4L2_BUF_FLAG_OUT_FENCE 0x00400000 >> >> /** >> * struct v4l2_exportbuffer - export of video buffer as DMABUF file descriptor >> > > Regards, > > Hans >