Re: [PATCH v3 9/9] media: subdev: Support single-stream case in v4l2_subdev_enable/disable_streams()

Umang Jain <umang.jain@xxxxxxxxxxxxxxxx> · Thu, 11 Apr 2024 16:32:02 +0530

Hi Tomi,

On 10/04/24 6:05 pm, Tomi Valkeinen wrote:
At the moment the v4l2_subdev_enable/disable_streams() functions call
fallback helpers to handle the case where the subdev only implements
.s_stream(), and the main function handles the case where the subdev
implements streams (V4L2_SUBDEV_FL_STREAMS, which implies
.enable/disable_streams()).

What is missing is support for subdevs which do not implement streams
support, but do implement .enable/disable_streams(). Example cases of
these subdevices are single-stream cameras, where using
.enable/disable_streams() is not required but helps us remove the users
of the legacy .s_stream(), and subdevices with multiple source pads (but
single stream per pad), where .enable/disable_streams() allows the
subdevice to control the enable/disable state per pad.

The two single-streams cases (.s_stream() and .enable/disable_streams())
are very similar, and with small changes we can change the
v4l2_subdev_enable/disable_streams() functions to support all three
cases, without needing separate fallback functions.

A few potentially problematic details, though:

Does this mean the patch needs to be worked upon more ?

I quickly tested the series by applying it locally with my use case of 
IMX283 .enable/disable streams and s_stream as the helper function and 
it seems I am still seeing the same behaviour as before (i.e. not being 
streamed) and have to carry the workaround as mentioned in [1] **NOTE**

[1] 
https://lore.kernel.org/linux-media/20240313070705.91140-1-umang.jain@xxxxxxxxxxxxxxxx/


- For the single-streams cases we use sd->enabled_pads field, which
   limits the number of pads for the subdevice to 64. For simplicity I
   added the check for this limitation to the beginning of the function,
   and it also applies to the streams case.

- The fallback functions only allowed the target pad to be a source pad.
   It is not very clear to me why this check was needed, but it was not
   needed in the streams case. However, I doubt the
   v4l2_subdev_enable/disable_streams() code has ever been tested with
   sink pads, so to be on the safe side, I added the same check
   to the v4l2_subdev_enable/disable_streams() functions.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
---
  drivers/media/v4l2-core/v4l2-subdev.c | 187 ++++++++++++++--------------------
  1 file changed, 79 insertions(+), 108 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 0d376d72ecc7..4a73886741f9 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -2106,6 +2106,13 @@ static void v4l2_subdev_collect_streams(struct v4l2_subdev *sd,
  					u64 *found_streams,
  					u64 *enabled_streams)
  {
+	if (!(sd->flags & V4L2_SUBDEV_FL_STREAMS)) {
+		*found_streams = BIT_ULL(0);
+		if (sd->enabled_pads & BIT_ULL(pad))
+			*enabled_streams = BIT_ULL(0);
+		return;
+	}
+
  	*found_streams = 0;
  	*enabled_streams = 0;
  
@@ -2127,6 +2134,14 @@ static void v4l2_subdev_set_streams_enabled(struct v4l2_subdev *sd,
  					    u32 pad, u64 streams_mask,
  					    bool enabled)
  {
+	if (!(sd->flags & V4L2_SUBDEV_FL_STREAMS)) {
+		if (enabled)
+			sd->enabled_pads |= BIT_ULL(pad);
+		else
+			sd->enabled_pads &= ~BIT_ULL(pad);
+		return;
+	}
+
  	for (unsigned int i = 0; i < state->stream_configs.num_configs; ++i) {
  		struct v4l2_subdev_stream_config *cfg =
  			&state->stream_configs.configs[i];
@@ -2136,51 +2151,6 @@ static void v4l2_subdev_set_streams_enabled(struct v4l2_subdev *sd,
  	}
  }
  
-static int v4l2_subdev_enable_streams_fallback(struct v4l2_subdev *sd, u32 pad,
-					       u64 streams_mask)
-{
-	struct device *dev = sd->entity.graph_obj.mdev->dev;
-	int ret;
-
-	/*
-	 * The subdev doesn't implement pad-based stream enable, fall back
-	 * to the .s_stream() operation.
-	 */
-	if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
-		return -EOPNOTSUPP;
-
-	/*
-	 * .s_stream() means there is no streams support, so only allowed stream
-	 * is the implicit stream 0.
-	 */
-	if (streams_mask != BIT_ULL(0))
-		return -EOPNOTSUPP;
-
-	/*
-	 * We use a 64-bit bitmask for tracking enabled pads, so only subdevices
-	 * with 64 pads or less can be supported.
-	 */
-	if (pad >= sizeof(sd->enabled_pads) * BITS_PER_BYTE)
-		return -EOPNOTSUPP;
-
-	if (sd->enabled_pads & BIT_ULL(pad)) {
-		dev_dbg(dev, "pad %u already enabled on %s\n",
-			pad, sd->entity.name);
-		return -EALREADY;
-	}
-
-	/* Start streaming when the first pad is enabled. */
-	if (!sd->enabled_pads) {
-		ret = v4l2_subdev_call(sd, video, s_stream, 1);
-		if (ret)
-			return ret;
-	}
-
-	sd->enabled_pads |= BIT_ULL(pad);
-
-	return 0;
-}
-
  int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
  			       u64 streams_mask)
  {
@@ -2189,21 +2159,33 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
  	bool already_streaming;
  	u64 enabled_streams;
  	u64 found_streams;
+	bool use_s_stream;
  	int ret;
  
  	/* A few basic sanity checks first. */
  	if (pad >= sd->entity.num_pads)
  		return -EINVAL;
  
+	if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
+		return -EOPNOTSUPP;
+
+	/*
+	 * We use a 64-bit bitmask for tracking enabled pads, so only subdevices
+	 * with 64 pads or less can be supported.
+	 */
+	if (pad >= sizeof(sd->enabled_pads) * BITS_PER_BYTE)
+		return -EOPNOTSUPP;
+
  	if (!streams_mask)
  		return 0;
  
  	/* Fallback on .s_stream() if .enable_streams() isn't available. */
-	if (!v4l2_subdev_has_op(sd, pad, enable_streams))
-		return v4l2_subdev_enable_streams_fallback(sd, pad,
-							   streams_mask);
+	use_s_stream = !v4l2_subdev_has_op(sd, pad, enable_streams);
  
-	state = v4l2_subdev_lock_and_get_active_state(sd);
+	if (!use_s_stream)
+		state = v4l2_subdev_lock_and_get_active_state(sd);
+	else
+		state = NULL;
  
  	/*
  	 * Verify that the requested streams exist and that they are not
@@ -2231,9 +2213,18 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
  
  	already_streaming = v4l2_subdev_is_streaming(sd);
  
-	/* Call the .enable_streams() operation. */
-	ret = v4l2_subdev_call(sd, pad, enable_streams, state, pad,
-			       streams_mask);
+	if (!use_s_stream) {
+		/* Call the .enable_streams() operation. */
+		ret = v4l2_subdev_call(sd, pad, enable_streams, state, pad,
+				       streams_mask);
+	} else {
+		/* Start streaming when the first pad is enabled. */
+		if (!already_streaming)
+			ret = v4l2_subdev_call(sd, video, s_stream, 1);
+		else
+			ret = 0;
+	}
+
  	if (ret) {
  		dev_dbg(dev, "enable streams %u:%#llx failed: %d\n", pad,
  			streams_mask, ret);
@@ -2243,34 +2234,32 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
  	/* Mark the streams as enabled. */
  	v4l2_subdev_set_streams_enabled(sd, state, pad, streams_mask, true);
  
-	if (!already_streaming)
+	if (!use_s_stream && !already_streaming)
  		v4l2_subdev_enable_privacy_led(sd);
  
  done:
-	v4l2_subdev_unlock_state(state);
+	if (!use_s_stream)
+		v4l2_subdev_unlock_state(state);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(v4l2_subdev_enable_streams);
  
-static int v4l2_subdev_disable_streams_fallback(struct v4l2_subdev *sd, u32 pad,
-						u64 streams_mask)
+int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
+				u64 streams_mask)
  {
  	struct device *dev = sd->entity.graph_obj.mdev->dev;
+	struct v4l2_subdev_state *state;
+	u64 enabled_streams;
+	u64 found_streams;
+	bool use_s_stream;
  	int ret;
  
-	/*
-	 * If the subdev doesn't implement pad-based stream enable, fall back
-	 * to the .s_stream() operation.
-	 */
-	if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
-		return -EOPNOTSUPP;
+	/* A few basic sanity checks first. */
+	if (pad >= sd->entity.num_pads)
+		return -EINVAL;
  
-	/*
-	 * .s_stream() means there is no streams support, so only allowed stream
-	 * is the implicit stream 0.
-	 */
-	if (streams_mask != BIT_ULL(0))
+	if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
  		return -EOPNOTSUPP;
  
  	/*
@@ -2280,46 +2269,16 @@ static int v4l2_subdev_disable_streams_fallback(struct v4l2_subdev *sd, u32 pad,
  	if (pad >= sizeof(sd->enabled_pads) * BITS_PER_BYTE)
  		return -EOPNOTSUPP;
  
-	if (!(sd->enabled_pads & BIT_ULL(pad))) {
-		dev_dbg(dev, "pad %u already disabled on %s\n",
-			pad, sd->entity.name);
-		return -EALREADY;
-	}
-
-	/* Stop streaming when the last streams are disabled. */
-	if (!(sd->enabled_pads & ~BIT_ULL(pad))) {
-		ret = v4l2_subdev_call(sd, video, s_stream, 0);
-		if (ret)
-			return ret;
-	}
-
-	sd->enabled_pads &= ~BIT_ULL(pad);
-
-	return 0;
-}
-
-int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
-				u64 streams_mask)
-{
-	struct device *dev = sd->entity.graph_obj.mdev->dev;
-	struct v4l2_subdev_state *state;
-	u64 enabled_streams;
-	u64 found_streams;
-	int ret;
-
-	/* A few basic sanity checks first. */
-	if (pad >= sd->entity.num_pads)
-		return -EINVAL;
-
  	if (!streams_mask)
  		return 0;
  
  	/* Fallback on .s_stream() if .disable_streams() isn't available. */
-	if (!v4l2_subdev_has_op(sd, pad, disable_streams))
-		return v4l2_subdev_disable_streams_fallback(sd, pad,
-							    streams_mask);
+	use_s_stream = !v4l2_subdev_has_op(sd, pad, disable_streams);
  
-	state = v4l2_subdev_lock_and_get_active_state(sd);
+	if (!use_s_stream)
+		state = v4l2_subdev_lock_and_get_active_state(sd);
+	else
+		state = NULL;
  
  	/*
  	 * Verify that the requested streams exist and that they are not
@@ -2345,9 +2304,19 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
  
  	dev_dbg(dev, "disable streams %u:%#llx\n", pad, streams_mask);
  
-	/* Call the .disable_streams() operation. */
-	ret = v4l2_subdev_call(sd, pad, disable_streams, state, pad,
-			       streams_mask);
+	if (!use_s_stream) {
+		/* Call the .disable_streams() operation. */
+		ret = v4l2_subdev_call(sd, pad, disable_streams, state, pad,
+				       streams_mask);
+	} else {
+		/* Stop streaming when the last streams are disabled. */
+
+		if (!(sd->enabled_pads & ~BIT_ULL(pad)))
+			ret = v4l2_subdev_call(sd, video, s_stream, 0);
+		else
+			ret = 0;
+	}
+
  	if (ret) {
  		dev_dbg(dev, "disable streams %u:%#llx failed: %d\n", pad,
  			streams_mask, ret);
@@ -2357,10 +2326,12 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
  	v4l2_subdev_set_streams_enabled(sd, state, pad, streams_mask, false);
  
  done:
-	if (!v4l2_subdev_is_streaming(sd))
-		v4l2_subdev_disable_privacy_led(sd);
+	if (!use_s_stream) {
+		if (!v4l2_subdev_is_streaming(sd))
+			v4l2_subdev_disable_privacy_led(sd);
  
-	v4l2_subdev_unlock_state(state);
+		v4l2_subdev_unlock_state(state);
+	}
  
  	return ret;
  }









