From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752556AbeEVMFc (ORCPT ); Tue, 22 May 2018 08:05:32 -0400 Received: from lb2-smtp-cloud7.xs4all.net ([194.109.24.28]:34196 "EHLO lb2-smtp-cloud7.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752065AbeEVMFU (ORCPT ); Tue, 22 May 2018 08:05:20 -0400 Subject: Re: [PATCH v10 11/16] vb2: add explicit fence user API To: Ezequiel Garcia , linux-media@vger.kernel.org Cc: kernel@collabora.com, Mauro Carvalho Chehab , Shuah Khan , Pawel Osciak , Alexandre Courbot , Sakari Ailus , Brian Starkey , linux-kernel@vger.kernel.org, Gustavo Padovan References: <20180521165946.11778-1-ezequiel@collabora.com> <20180521165946.11778-12-ezequiel@collabora.com> From: Hans Verkuil Message-ID: <9a7d4128-571e-468c-8c03-9f35f610a87f@xs4all.nl> Date: Tue, 22 May 2018 14:05:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180521165946.11778-12-ezequiel@collabora.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4wfP60snJ+G31TytbFpG9n7to7041hR927STcVhjTy6aIwaxF9vedZ5VIAUcqV0AXKpmvZ7v8wspBJ3JkcCWYCPuUrbD1UlDM5bFNXssYLjfU55JZxUz6q OEnuz6x59jwQc4GrAKGOmOUliroABTpQBaZEQvxnI5Lm2am/6YN7nuXkEc1l8S1uJHyy7vixr8Kb2BYnMZVRc2arEeI5dSGIGaZTs9/245af09d5dcIVuo3Q wmufaRks76HWKfmMZSZ8nkpve6cFJNXPDv8LUj6xN2icmU1xkcahYty21bT1gSdoBc3JZpGD6YAe3cYuZInM0mB5goR7OkgXycDgXz5m6iHsYkquQtuClWDE WM3cgSdQH1trViubruiXzHbpisfWnDPIjAfM18lNBOsNHqYt2vqnhb0CgIUulnLWDPyY9/6c8lUq2IwLbdP0EqGpc5k4RcvNNVOtFQQ+jHjq78NSRxZN8UAb JO7mlQHXtqal6bU7vpegAK8EkKjZVJa7fqUlaumyqon6h05h8a7SIS3gMbpAXzG6SAV7gZNiI4/sKnQu3Z2oAAbA45Em23doH9RYNaXQCVAMfM/3rl8rxExz NGLPqZ8rcDNU1+0BkzTA1j4/ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/05/18 18:59, Ezequiel Garcia wrote: > From: Gustavo Padovan > > Turn the reserved2 field into fence_fd that we will use to send > an in-fence to the kernel or 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 an in-fence to the kernel to be waited on, and > V4L2_BUF_FLAG_OUT_FENCE, to ask the kernel to give back an out-fence. > > v8: return -1 if new flags are set. > v7: minor fixes on the Documentation (Hans Verkuil) > > v6: big improvement on doc (Hans Verkuil) > > v5: - keep using reserved2 field for cpia2 > - set fence_fd to 0 for now, for compat with userspace(Mauro) > > v4: make it a union with reserved2 and fence_fd (Hans Verkuil) > > v3: make the out_fence refer to the current buffer (Hans Verkuil) > > v2: add documentation > > Signed-off-by: Gustavo Padovan > --- > Documentation/media/uapi/v4l/buffer.rst | 48 ++++++++++++++++++++++--- > drivers/media/common/videobuf2/videobuf2-v4l2.c | 6 +++- > drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 4 +-- > include/uapi/linux/videodev2.h | 8 ++++- > 4 files changed, 58 insertions(+), 8 deletions(-) > > diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst > index e2c85ddc990b..971b7453040c 100644 > --- a/Documentation/media/uapi/v4l/buffer.rst > +++ b/Documentation/media/uapi/v4l/buffer.rst > @@ -300,11 +300,23 @@ struct v4l2_buffer > multi-planar API the application sets this to the number of > elements in the ``planes`` array. The driver will fill in the > actual number of valid elements in that array. > - * - __u32 > - - ``reserved2`` > + * - __s32 > + - ``fence_fd`` > - > - - A place holder for future extensions. Drivers and applications > - must set this to 0. > + - Used to communicate a fence file descriptor from userspace to kernel > + and vice-versa. On :ref:`VIDIOC_QBUF ` when sending > + an in-fence for V4L2 to wait on, the ``V4L2_BUF_FLAG_IN_FENCE`` flag must > + be used and this field set to the fence file descriptor of the in-fence. > + If the in-fence is not valid ` VIDIOC_QBUF`` returns an error. > + > + To get an out-fence back from V4L2 the ``V4L2_BUF_FLAG_OUT_FENCE`` > + must be set, the kernel will return the out-fence file descriptor in > + this field. If it fails to create the out-fence ``VIDIOC_QBUF` returns > + an error. > + > + For all other ioctls V4L2 sets this field to -1 if > + ``V4L2_BUF_FLAG_IN_FENCE`` and/or ``V4L2_BUF_FLAG_OUT_FENCE`` are set, > + otherwise this field is set to 0 for backward compatibility. > * - __u32 > - ``reserved`` > - > @@ -648,6 +660,34 @@ 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 the fence passed in the ``fence_fd`` field. The > + buffer won't be queued to the driver until the fence signals. The order > + in which buffers are queued is guaranteed to be preserved, so any > + buffers queued after this buffer will also be blocked until this fence > + signals. This flag must be set before calling ``VIDIOC_QBUF``. For > + other ioctls the driver just reports the value of the flag. > + > + If the fence signals the flag is cleared and not reported anymore. > + If the fence is not valid ``VIDIOC_QBUF`` returns an error. > + * .. _`V4L2-BUF-FLAG-OUT-FENCE`: > + > + - ``V4L2_BUF_FLAG_OUT_FENCE`` > + - 0x00400000 > + - Request for a fence to be attached to the buffer. The driver will fill > + in the out-fence fd in the ``fence_fd`` field when :ref:`VIDIOC_QBUF > + ` returns. This flag must be set before calling > + ``VIDIOC_QBUF``. This flag is only an input, and is not set by the kernel. > + > + If the creation of the out-fence fails ``VIDIOC_QBUF`` returns an > + error. > + > + Note that it is valid to set both ``V4L2_BUF_FLAG_IN_FENCE`` and > + `V4L2_BUF_FLAG_OUT_FENCE`` flags. In such case, the ``fence_fd`` > + field is used to both set the in-fence and return the out-fence. > > > > diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c > index 64503615d00b..8312f61adfa6 100644 > --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c > @@ -203,9 +203,13 @@ 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->reserved = 0; > > + if (b->flags & (V4L2_BUF_FLAG_IN_FENCE | V4L2_BUF_FLAG_OUT_FENCE)) > + b->fence_fd = -1; > + else > + b->fence_fd = 0; I don't see why we can't just always set fence_fd to -1. There is no need for backwards compatibility that I can see. Regards, Hans > + > if (q->is_multiplanar) { > /* > * Fill in plane-related data if userspace provided an array > diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > index 4312935f1dfc..93c752459aec 100644 > --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > @@ -388,7 +388,7 @@ struct v4l2_buffer32 { > __s32 fd; > } m; > __u32 length; > - __u32 reserved2; > + __s32 fence_fd; > __u32 reserved; > }; > > @@ -606,7 +606,7 @@ static int put_v4l2_buffer32(struct v4l2_buffer __user *kp, > assign_in_user(&up->timestamp.tv_usec, &kp->timestamp.tv_usec) || > copy_in_user(&up->timecode, &kp->timecode, sizeof(kp->timecode)) || > assign_in_user(&up->sequence, &kp->sequence) || > - assign_in_user(&up->reserved2, &kp->reserved2) || > + assign_in_user(&up->fence_fd, &kp->fence_fd) || > assign_in_user(&up->reserved, &kp->reserved) || > get_user(length, &kp->length) || > put_user(length, &up->length)) > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h > index a8842a5ca636..1f18dc68ecab 100644 > --- a/include/uapi/linux/videodev2.h > +++ b/include/uapi/linux/videodev2.h > @@ -934,7 +934,10 @@ struct v4l2_buffer { > __s32 fd; > } m; > __u32 length; > - __u32 reserved2; > + union { > + __s32 fence_fd; > + __u32 reserved2; > + }; > __u32 reserved; > }; > > @@ -971,6 +974,9 @@ struct v4l2_buffer { > #define V4L2_BUF_FLAG_TSTAMP_SRC_SOE 0x00010000 > /* mem2mem encoder/decoder */ > #define V4L2_BUF_FLAG_LAST 0x00100000 > +/* Explicit synchronization */ > +#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 >