[RFC PATCH 3/6] v4l2-ioctl.c: use correct vb2_queue lock for m2m devices

[Hans Verkuil <hverkuil@xs4all.nl>]

From: Hans Verkuil <hansverk@cisco.com>

For m2m devices the vdev->queue lock was always taken instead of the
lock for the specific capture or output queue. Now that we pushed
the locking down into __video_do_ioctl() we can pick the correct
lock and improve the performance of m2m devices.

Signed-off-by: Hans Verkuil <hansverk@cisco.com>
---
 drivers/media/v4l2-core/v4l2-ioctl.c | 59 +++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index a12c66ead30d..b871b8fe5105 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -29,6 +29,7 @@
 #include <media/v4l2-device.h>
 #include <media/videobuf2-v4l2.h>
 #include <media/v4l2-mc.h>
+#include <media/v4l2-mem2mem.h>
 
 #include <trace/events/v4l2.h>
 
@@ -2626,12 +2627,64 @@ static bool v4l2_is_known_ioctl(unsigned int cmd)
 	return v4l2_ioctls[_IOC_NR(cmd)].ioctl == cmd;
 }
 
-static struct mutex *v4l2_ioctl_get_lock(struct video_device *vdev, unsigned cmd)
+#if IS_ENABLED(CONFIG_V4L2_MEM2MEM_DEV)
+static bool v4l2_ioctl_m2m_queue_is_output(unsigned int cmd, void *arg)
+{
+	switch (cmd) {
+	case VIDIOC_CREATE_BUFS: {
+		struct v4l2_create_buffers *cbufs = arg;
+
+		return V4L2_TYPE_IS_OUTPUT(cbufs->format.type);
+	}
+	case VIDIOC_REQBUFS: {
+		struct v4l2_requestbuffers *rbufs = arg;
+
+		return V4L2_TYPE_IS_OUTPUT(rbufs->type);
+	}
+	case VIDIOC_QBUF:
+	case VIDIOC_DQBUF:
+	case VIDIOC_QUERYBUF:
+	case VIDIOC_PREPARE_BUF: {
+		struct v4l2_buffer *buf = arg;
+
+		return V4L2_TYPE_IS_OUTPUT(buf->type);
+	}
+	case VIDIOC_EXPBUF: {
+		struct v4l2_exportbuffer *expbuf = arg;
+
+		return V4L2_TYPE_IS_OUTPUT(expbuf->type);
+	}
+	case VIDIOC_STREAMON:
+	case VIDIOC_STREAMOFF: {
+		int *type = arg;
+
+		return V4L2_TYPE_IS_OUTPUT(*type);
+	}
+	default:
+		return false;
+	}
+}
+#endif
+
+static struct mutex *v4l2_ioctl_get_lock(struct video_device *vdev,
+					 struct v4l2_fh *vfh, unsigned cmd,
+					 void *arg)
 {
 	if (_IOC_NR(cmd) >= V4L2_IOCTLS)
 		return vdev->lock;
 	if (test_bit(_IOC_NR(cmd), vdev->disable_locking))
 		return NULL;
+#if IS_ENABLED(CONFIG_V4L2_MEM2MEM_DEV)
+	if (vfh && vfh->m2m_ctx &&
+	    (v4l2_ioctls[_IOC_NR(cmd)].flags & INFO_FL_QUEUE)) {
+		bool is_output = v4l2_ioctl_m2m_queue_is_output(cmd, arg);
+		struct v4l2_m2m_queue_ctx *ctx = is_output ?
+			&vfh->m2m_ctx->out_q_ctx : &vfh->m2m_ctx->cap_q_ctx;
+
+		if (ctx->q.lock)
+			return ctx->q.lock;
+	}
+#endif
 	if (vdev->queue && vdev->queue->lock &&
 			(v4l2_ioctls[_IOC_NR(cmd)].flags & INFO_FL_QUEUE))
 		return vdev->queue->lock;
@@ -2679,7 +2732,7 @@ static long __video_do_ioctl(struct file *file,
 		unsigned int cmd, void *arg)
 {
 	struct video_device *vfd = video_devdata(file);
-	struct mutex *lock = v4l2_ioctl_get_lock(vfd, cmd);
+	struct mutex *lock;
 	const struct v4l2_ioctl_ops *ops = vfd->ioctl_ops;
 	bool write_only = false;
 	struct v4l2_ioctl_info default_info;
@@ -2698,6 +2751,8 @@ static long __video_do_ioctl(struct file *file,
 	if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags))
 		vfh = file->private_data;
 
+	lock = v4l2_ioctl_get_lock(vfd, vfh, cmd, arg);
+
 	if (lock && mutex_lock_interruptible(lock))
 		return -ERESTARTSYS;
 
-- 
2.17.0