linux-kernel - Re: [RFC v4 15/17] [media] vb2: add infrastructure to support out-fences

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Message-ID: <20171027094105.GE40170@e107564-lin.cambridge.arm.com>
Date:   Fri, 27 Oct 2017 10:41:05 +0100
From:   Brian Starkey <brian.starkey@....com>
To:     Gustavo Padovan <gustavo@...ovan.org>
Cc:     linux-media@...r.kernel.org, Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@....samsung.com>,
        Shuah Khan <shuahkh@....samsung.com>,
        Pawel Osciak <pawel@...iak.com>,
        Alexandre Courbot <acourbot@...omium.org>,
        Sakari Ailus <sakari.ailus@....fi>,
        linux-kernel@...r.kernel.org,
        Gustavo Padovan <gustavo.padovan@...labora.com>
Subject: Re: [RFC v4 15/17] [media] vb2: add infrastructure to support
 out-fences

Hi Gustavo,

Sorry for the sporadic review... I'm struggling to get time to look at
these.

On Fri, Oct 20, 2017 at 07:50:10PM -0200, Gustavo Padovan wrote:
>From: Gustavo Padovan <gustavo.padovan@...labora.com>
>
>Add vb2_setup_out_fence() and the needed members to struct vb2_buffer.
>
>v2:	- change it to reflect fd_install at DQEVENT
>	- add fence context for out-fences
>
>Signed-off-by: Gustavo Padovan <gustavo.padovan@...labora.com>
>---
> drivers/media/v4l2-core/videobuf2-core.c | 31 +++++++++++++++++++++++++++++++
> include/media/videobuf2-core.h           | 20 ++++++++++++++++++++
> 2 files changed, 51 insertions(+)
>
>diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
>index 78f369dba3e3..c7ba67bda5ac 100644
>--- a/drivers/media/v4l2-core/videobuf2-core.c
>+++ b/drivers/media/v4l2-core/videobuf2-core.c
>@@ -23,8 +23,11 @@
> #include <linux/sched.h>
> #include <linux/freezer.h>
> #include <linux/kthread.h>
>+#include <linux/sync_file.h>
>+#include <linux/dma-fence.h>
>
> #include <media/videobuf2-core.h>
>+#include <media/videobuf2-fence.h>
> #include <media/v4l2-mc.h>
>
> #include <trace/events/vb2.h>
>@@ -1316,6 +1319,34 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
> }
> EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
>
>+int vb2_setup_out_fence(struct vb2_queue *q, unsigned int index)
>+{
>+	struct vb2_buffer *vb;
>+	struct dma_fence *fence;
>+
>+	vb = q->bufs[index];
>+
>+	vb->out_fence_fd = get_unused_fd_flags(O_CLOEXEC);
>+
>+	fence = vb2_fence_alloc(q->out_fence_context);
>+	if (!fence) {
>+		put_unused_fd(vb->out_fence_fd);
>+		return -ENOMEM;
>+	}
>+
>+	vb->sync_file = sync_file_create(fence);
>+	if (!vb->sync_file) {
>+		dma_fence_put(fence);
>+		put_unused_fd(vb->out_fence_fd);
>+		return -ENOMEM;
>+	}

sync_file_create() takes an extra reference of its own, so I think you
don't need the dma_fence_get() below, or you should drop a reference
before returning.

-Brian

>+
>+	vb->out_fence = dma_fence_get(fence);
>+
>+	return 0;
>+}
>+EXPORT_SYMBOL_GPL(vb2_setup_out_fence);
>+
> /**
>  * vb2_start_streaming() - Attempt to start streaming.
>  * @q:		videobuf2 queue
>diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>index 624ca2dce9ea..1925ede73804 100644
>--- a/include/media/videobuf2-core.h
>+++ b/include/media/videobuf2-core.h
>@@ -259,6 +259,10 @@ struct vb2_buffer {
> 	 *			using the buffer (queueing to the driver)
> 	 * fence_cb:		fence callback information
> 	 * fence_cb_lock:	protect callback signal/remove
>+	 * out_fence_fd:	the out_fence_fd to be shared with userspace.
>+	 * out_fence:		the out-fence associated with the buffer once
>+	 *			it is queued to the driver.
>+	 * sync_file:		the sync file to wrap the out fence
> 	 */
> 	enum vb2_buffer_state	state;
>
>@@ -269,6 +273,10 @@ struct vb2_buffer {
> 	struct dma_fence_cb	fence_cb;
> 	spinlock_t              fence_cb_lock;
>
>+	int			out_fence_fd;
>+	struct dma_fence	*out_fence;
>+	struct sync_file	*sync_file;
>+
> #ifdef CONFIG_VIDEO_ADV_DEBUG
> 	/*
> 	 * Counters for how often these buffer-related ops are
>@@ -518,6 +526,7 @@ struct vb2_buf_ops {
>  * @ordered_in_vb2: set by the driver to tell vb2 te guarantee the order
>  *		of buffer queue from userspace with QBUF() until they are
>  *		queued to the driver.
>+ * @out_fence_context: the fence context for the out fences
>  * @last_fence:	last in-fence received. Used to keep ordering.
>  * @fileio:	file io emulator internal data, used only if emulator is active
>  * @threadio:	thread io internal data, used only if thread is active
>@@ -574,6 +583,7 @@ struct vb2_queue {
> 	unsigned int			ordered_in_driver:1;
> 	unsigned int			ordered_in_vb2:1;
>
>+	u64				out_fence_context;
> 	struct dma_fence		*last_fence;
>
> 	struct vb2_fileio_data		*fileio;
>@@ -745,6 +755,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
>
> /**
>+ * vb2_setup_out_fence() - setup new out-fence
>+ * @q:		The vb2_queue where to setup it
>+ * @index:	index of the buffer
>+ *
>+ * Setup the file descriptor, the fence and the sync_file for the next
>+ * buffer to be queued and add everything to the tail of the q->out_fence_list.
>+ */
>+int vb2_setup_out_fence(struct vb2_queue *q, unsigned int index);
>+
>+/**
>  * vb2_core_qbuf() - Queue a buffer from userspace
>  *
>  * @q:		videobuf2 queue
>-- 
>2.13.6
>