[PATCH v7 1/4] media: v4l2-mem2mem: handle draining, stopped and next-buf-is-last states

From: Neil Armstrong
Date: Tue Mar 03 2020 - 09:33:30 EST


Since the draining and stop phase of the HW decoder mem2mem bahaviour is
now clearly defined, we can move handling of the following states to the
common v4l2-mem2mem core code:
- draining
- stopped
- next-buf-is-last

By introducing the following v4l2-mem2mem APIs:
- v4l2_m2m_encoder_cmd/v4l2_m2m_ioctl_encoder_cmd to handle start/stop command
- v4l2_m2m_decoder_cmd/v4l2_m2m_ioctl_decoder_cmd to handle start/stop command
- v4l2_m2m_update_start_streaming_state to update state on start of streaming
of the de/encoder queue
- v4l2_m2m_update_stop_streaming_state to update state on stop of streaming
of the de/encoder queue
- v4l2_m2m_last_buffer_done to make the current dest buffer as the last one

And inline helpers:
- v4l2_m2m_mark_stopped to mark the de/encoding process as stopped
- v4l2_m2m_clear_state to clear the de/encoding state
- v4l2_m2m_dst_buf_is_last to detect the current dequeued dst_buf is the last
- v4l2_m2m_has_stopped to detect the de/encoding stopped state
- v4l2_m2m_is_last_draining_src_buf to detect the current source buffer should
be the last processing before stopping the de/encoding process

The special next-buf-is-last when min_buffers != 1 case is also handled
in v4l2_m2m_qbuf() by reusing the other introduced APIs.

This state management has been stolen from the vicodec implementation,
and is no-op for drivers not calling the v4l2_m2m_encoder_cmd or
v4l2_m2m_decoder_cmd and v4l2_m2m_update_start/stop_streaming_state.

The vicodec will be the first one to be converted as an example.

Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
---
drivers/media/v4l2-core/v4l2-mem2mem.c | 221 ++++++++++++++++++++++++-
include/media/v4l2-mem2mem.h | 133 +++++++++++++++
2 files changed, 352 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 1afd9c6ad908..c4a84d9f693a 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -340,6 +340,11 @@ static void __v4l2_m2m_try_queue(struct v4l2_m2m_dev *m2m_dev,
m2m_ctx->new_frame = !dst->vb2_buf.copied_timestamp ||
dst->vb2_buf.timestamp != src->vb2_buf.timestamp;

+ if (m2m_ctx->has_stopped) {
+ dprintk("Device has stopped\n");
+ goto job_unlock;
+ }
+
if (m2m_dev->m2m_ops->job_ready
&& (!m2m_dev->m2m_ops->job_ready(m2m_ctx->priv))) {
dprintk("Driver not ready\n");
@@ -556,6 +561,140 @@ int v4l2_m2m_querybuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
}
EXPORT_SYMBOL_GPL(v4l2_m2m_querybuf);

+/*
+ * This will add the LAST flag and mark the buffer management
+ * state as stopped.
+ * This is called when the last capture buffer must be flagged as LAST
+ * in draining mode from the encoder/decoder driver buf_queue() callback
+ * or from v4l2_update_last_buf_state() when a capture buffer is available.
+ */
+void v4l2_m2m_last_buffer_done(struct v4l2_m2m_ctx *m2m_ctx,
+ struct vb2_v4l2_buffer *vbuf)
+{
+ vbuf->flags |= V4L2_BUF_FLAG_LAST;
+ vb2_buffer_done(&vbuf->vb2_buf, VB2_BUF_STATE_DONE);
+
+ v4l2_m2m_mark_stopped(m2m_ctx);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_last_buffer_done);
+
+/* When stop command is issued, update buffer management state */
+static int v4l2_update_last_buf_state(struct v4l2_m2m_ctx *m2m_ctx)
+{
+ struct vb2_v4l2_buffer *next_dst_buf;
+
+ if (m2m_ctx->is_draining)
+ return -EBUSY;
+
+ if (m2m_ctx->has_stopped)
+ return 0;
+
+ m2m_ctx->last_src_buf = v4l2_m2m_last_src_buf(m2m_ctx);
+ m2m_ctx->is_draining = true;
+
+ /*
+ * The processing of the last output buffer queued before
+ * the STOP command is expected to mark the buffer management
+ * state as stopped with v4l2_m2m_mark_stopped().
+ */
+ if (m2m_ctx->last_src_buf)
+ return 0;
+
+ /*
+ * In case the output queue is empty, try to mark the last capture
+ * buffer as LAST.
+ */
+ next_dst_buf = v4l2_m2m_dst_buf_remove(m2m_ctx);
+ if (!next_dst_buf) {
+ /*
+ * Wait for the next queued one in encoder/decoder driver
+ * buf_queue() callback using the v4l2_m2m_dst_buf_is_last()
+ * helper or in v4l2_m2m_qbuf() if encoder/decoder is not yet
+ * streaming.
+ */
+ m2m_ctx->next_buf_last = true;
+ return 0;
+ }
+
+ v4l2_m2m_last_buffer_done(m2m_ctx, next_dst_buf);
+
+ return 0;
+}
+
+/*
+ * Updates the encoding/decoding buffer management state, should
+ * be called from encoder/decoder drivers start_streaming()
+ */
+void v4l2_m2m_update_start_streaming_state(struct v4l2_m2m_ctx *m2m_ctx,
+ struct vb2_queue *q)
+{
+ /* If start streaming again, untag the last output buffer */
+ if (V4L2_TYPE_IS_OUTPUT(q->type))
+ m2m_ctx->last_src_buf = NULL;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_update_start_streaming_state);
+
+/*
+ * Updates the encoding/decoding buffer management state, should
+ * be called from encoder/decoder driver stop_streaming()
+ */
+void v4l2_m2m_update_stop_streaming_state(struct v4l2_m2m_ctx *m2m_ctx,
+ struct vb2_queue *q)
+{
+ if (V4L2_TYPE_IS_OUTPUT(q->type)) {
+ /*
+ * If in draining state, either mark next dst buffer as
+ * done or flag next one to be marked as done either
+ * in encoder/decoder driver buf_queue() callback using
+ * the v4l2_m2m_dst_buf_is_last() helper or in v4l2_m2m_qbuf()
+ * if encoder/decoder is not yet streaming
+ */
+ if (m2m_ctx->is_draining) {
+ struct vb2_v4l2_buffer *next_dst_buf;
+
+ m2m_ctx->last_src_buf = NULL;
+ next_dst_buf = v4l2_m2m_dst_buf_remove(m2m_ctx);
+ if (!next_dst_buf)
+ m2m_ctx->next_buf_last = true;
+ else
+ v4l2_m2m_last_buffer_done(m2m_ctx,
+ next_dst_buf);
+ }
+ } else {
+ v4l2_m2m_clear_state(m2m_ctx);
+ }
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_update_stop_streaming_state);
+
+static void v4l2_m2m_force_last_buf_done(struct v4l2_m2m_ctx *m2m_ctx,
+ struct vb2_queue *q)
+{
+ struct vb2_buffer *vb;
+ struct vb2_v4l2_buffer *vbuf;
+ unsigned int i;
+
+ if (WARN_ON(q->is_output))
+ return;
+ if (list_empty(&q->queued_list))
+ return;
+
+ vb = list_first_entry(&q->queued_list, struct vb2_buffer, queued_entry);
+ for (i = 0; i < vb->num_planes; i++)
+ vb2_set_plane_payload(vb, i, 0);
+
+ /*
+ * Since the buffer hasn't been queued to the ready queue,
+ * mark is active and owned before marking it LAST and DONE
+ */
+ vb->state = VB2_BUF_STATE_ACTIVE;
+ atomic_inc(&q->owned_by_drv_count);
+
+ vbuf = to_vb2_v4l2_buffer(vb);
+ vbuf->field = V4L2_FIELD_NONE;
+
+ v4l2_m2m_last_buffer_done(m2m_ctx, vbuf);
+}
+
int v4l2_m2m_qbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
struct v4l2_buffer *buf)
{
@@ -570,11 +709,25 @@ int v4l2_m2m_qbuf(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
__func__);
return -EPERM;
}
+
ret = vb2_qbuf(vq, vdev->v4l2_dev->mdev, buf);
- if (!ret && !(buf->flags & V4L2_BUF_FLAG_IN_REQUEST))
+ if (ret)
+ return ret;
+
+ /*
+ * If the capture queue is streaming, but streaming hasn't started
+ * on the device, but was asked to stop, mark the previously queued
+ * buffer as DONE with LAST flag since it won't be queued on the
+ * device.
+ */
+ if (!V4L2_TYPE_IS_OUTPUT(vq->type) &&
+ vb2_is_streaming(vq) && !vb2_start_streaming_called(vq) &&
+ (v4l2_m2m_has_stopped(m2m_ctx) || v4l2_m2m_dst_buf_is_last(m2m_ctx)))
+ v4l2_m2m_force_last_buf_done(m2m_ctx, vq);
+ else if (!(buf->flags & V4L2_BUF_FLAG_IN_REQUEST))
v4l2_m2m_try_schedule(m2m_ctx);

- return ret;
+ return 0;
}
EXPORT_SYMBOL_GPL(v4l2_m2m_qbuf);

@@ -1225,6 +1378,70 @@ int v4l2_m2m_ioctl_try_decoder_cmd(struct file *file, void *fh,
}
EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_try_decoder_cmd);

+/*
+ * Updates the encoding state on ENC_CMD_STOP/ENC_CMD_START
+ * Should be called from the encoder driver encoder_cmd() callback
+ */
+int v4l2_m2m_encoder_cmd(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+ struct v4l2_encoder_cmd *ec)
+{
+ if (ec->cmd != V4L2_ENC_CMD_STOP && ec->cmd != V4L2_ENC_CMD_START)
+ return -EINVAL;
+
+ if (ec->cmd == V4L2_ENC_CMD_STOP)
+ return v4l2_update_last_buf_state(m2m_ctx);
+
+ if (m2m_ctx->is_draining)
+ return -EBUSY;
+
+ if (m2m_ctx->has_stopped)
+ m2m_ctx->has_stopped = false;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_encoder_cmd);
+
+/*
+ * Updates the decoding state on DEC_CMD_STOP/DEC_CMD_START
+ * Should be called from the decoder driver decoder_cmd() callback
+ */
+int v4l2_m2m_decoder_cmd(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+ struct v4l2_decoder_cmd *dc)
+{
+ if (dc->cmd != V4L2_DEC_CMD_STOP && dc->cmd != V4L2_DEC_CMD_START)
+ return -EINVAL;
+
+ if (dc->cmd == V4L2_DEC_CMD_STOP)
+ return v4l2_update_last_buf_state(m2m_ctx);
+
+ if (m2m_ctx->is_draining)
+ return -EBUSY;
+
+ if (m2m_ctx->has_stopped)
+ m2m_ctx->has_stopped = false;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_decoder_cmd);
+
+int v4l2_m2m_ioctl_encoder_cmd(struct file *file, void *priv,
+ struct v4l2_encoder_cmd *ec)
+{
+ struct v4l2_fh *fh = file->private_data;
+
+ return v4l2_m2m_encoder_cmd(file, fh->m2m_ctx, ec);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_encoder_cmd);
+
+int v4l2_m2m_ioctl_decoder_cmd(struct file *file, void *priv,
+ struct v4l2_decoder_cmd *dc)
+{
+ struct v4l2_fh *fh = file->private_data;
+
+ return v4l2_m2m_decoder_cmd(file, fh->m2m_ctx, dc);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_ioctl_decoder_cmd);
+
int v4l2_m2m_ioctl_stateless_try_decoder_cmd(struct file *file, void *fh,
struct v4l2_decoder_cmd *dc)
{
diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index 1d85e24791e4..98753f00df7e 100644
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -80,6 +80,10 @@ struct v4l2_m2m_queue_ctx {
* for an existing frame. This is always true unless
* V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF is set, which
* indicates slicing support.
+ * @is_draining: indicates device is in draining phase
+ * @last_src_buf: indicate the last source buffer for draining
+ * @next_buf_last: next capture queud buffer will be tagged as last
+ * @has_stopped: indicate the device has been stopped
* @m2m_dev: opaque pointer to the internal data to handle M2M context
* @cap_q_ctx: Capture (output to memory) queue context
* @out_q_ctx: Output (input from memory) queue context
@@ -98,6 +102,11 @@ struct v4l2_m2m_ctx {

bool new_frame;

+ bool is_draining;
+ struct vb2_v4l2_buffer *last_src_buf;
+ bool next_buf_last;
+ bool has_stopped;
+
/* internal use only */
struct v4l2_m2m_dev *m2m_dev;

@@ -215,6 +224,86 @@ v4l2_m2m_buf_done(struct vb2_v4l2_buffer *buf, enum vb2_buffer_state state)
vb2_buffer_done(&buf->vb2_buf, state);
}

+/**
+ * v4l2_m2m_clear_state() - clear encoding/decoding state
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ */
+static inline void
+v4l2_m2m_clear_state(struct v4l2_m2m_ctx *m2m_ctx)
+{
+ m2m_ctx->next_buf_last = false;
+ m2m_ctx->is_draining = false;
+ m2m_ctx->has_stopped = false;
+}
+
+/**
+ * v4l2_m2m_mark_stopped() - set current encoding/decoding state as stopped
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ */
+static inline void
+v4l2_m2m_mark_stopped(struct v4l2_m2m_ctx *m2m_ctx)
+{
+ m2m_ctx->next_buf_last = false;
+ m2m_ctx->is_draining = false;
+ m2m_ctx->has_stopped = true;
+}
+
+/**
+ * v4l2_m2m_dst_buf_is_last() - return the current encoding/decoding session
+ * draining management state of next queued capture buffer
+ *
+ * This last capture buffer should be tagged with V4L2_BUF_FLAG_LAST to notify
+ * the end of the capture session.
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ */
+static inline bool
+v4l2_m2m_dst_buf_is_last(struct v4l2_m2m_ctx *m2m_ctx)
+{
+ return m2m_ctx->is_draining && m2m_ctx->next_buf_last;
+}
+
+/**
+ * v4l2_m2m_has_stopped() - return the current encoding/decoding session
+ * stopped state
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ */
+static inline bool
+v4l2_m2m_has_stopped(struct v4l2_m2m_ctx *m2m_ctx)
+{
+ return m2m_ctx->has_stopped;
+}
+
+/**
+ * v4l2_m2m_is_last_draining_src_buf() - return the output buffer draining
+ * state in the current encoding/decoding session
+ *
+ * This will identify the last output buffer queued before a session stop
+ * was required, leading to an actual encoding/decoding session stop state
+ * in the encoding/decoding process after being processed.
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ * @vbuf: pointer to struct &v4l2_buffer
+ */
+static inline bool
+v4l2_m2m_is_last_draining_src_buf(struct v4l2_m2m_ctx *m2m_ctx,
+ struct vb2_v4l2_buffer *vbuf)
+{
+ return m2m_ctx->is_draining && vbuf == m2m_ctx->last_src_buf;
+}
+
+/**
+ * v4l2_m2m_last_buffer_done() - marks the buffer with LAST flag and DONE
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ * @vbuf: pointer to struct &v4l2_buffer
+ */
+void v4l2_m2m_last_buffer_done(struct v4l2_m2m_ctx *m2m_ctx,
+ struct vb2_v4l2_buffer *vbuf);
+
/**
* v4l2_m2m_reqbufs() - multi-queue-aware REQBUFS multiplexer
*
@@ -312,6 +401,46 @@ int v4l2_m2m_streamon(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
int v4l2_m2m_streamoff(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
enum v4l2_buf_type type);

+/**
+ * v4l2_m2m_update_start_streaming_state() - update the encoding/decoding
+ * session state when a start of streaming of a video queue is requested
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ * @q: queue
+ */
+void v4l2_m2m_update_start_streaming_state(struct v4l2_m2m_ctx *m2m_ctx,
+ struct vb2_queue *q);
+
+/**
+ * v4l2_m2m_update_stop_streaming_state() - update the encoding/decoding
+ * session state when a stop of streaming of a video queue is requested
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ * @q: queue
+ */
+void v4l2_m2m_update_stop_streaming_state(struct v4l2_m2m_ctx *m2m_ctx,
+ struct vb2_queue *q);
+
+/**
+ * v4l2_m2m_encoder_cmd() - execute an encoder command
+ *
+ * @file: pointer to struct &file
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ * @ec: pointer to the encoder command
+ */
+int v4l2_m2m_encoder_cmd(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+ struct v4l2_encoder_cmd *ec);
+
+/**
+ * v4l2_m2m_decoder_cmd() - execute a decoder command
+ *
+ * @file: pointer to struct &file
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ * @dc: pointer to the decoder command
+ */
+int v4l2_m2m_decoder_cmd(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
+ struct v4l2_decoder_cmd *dc);
+
/**
* v4l2_m2m_poll() - poll replacement, for destination buffers only
*
@@ -704,6 +833,10 @@ int v4l2_m2m_ioctl_streamon(struct file *file, void *fh,
enum v4l2_buf_type type);
int v4l2_m2m_ioctl_streamoff(struct file *file, void *fh,
enum v4l2_buf_type type);
+int v4l2_m2m_ioctl_encoder_cmd(struct file *file, void *fh,
+ struct v4l2_encoder_cmd *ec);
+int v4l2_m2m_ioctl_decoder_cmd(struct file *file, void *fh,
+ struct v4l2_decoder_cmd *dc);
int v4l2_m2m_ioctl_try_encoder_cmd(struct file *file, void *fh,
struct v4l2_encoder_cmd *ec);
int v4l2_m2m_ioctl_try_decoder_cmd(struct file *file, void *fh,
--
2.22.0