Re: [PATCH v3 15/29] media: v4l2-subdev: Return dynamically allocated pass-through routes

On Mon, Aug 24, 2026 at 03:14:37PM +0300, Sakari Ailus wrote:
> Count the number of pass-through routes, allocate memory and then return
> the full table to the caller.
>
> Signed-off-by: Sakari Ailus <[email protected]>
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 61 +++++++++++++++++++++++----
>  1 file changed, 52 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index c9f38b0313eb..d34704aad88e 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -2561,13 +2561,42 @@ int __v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
>  	struct media_pad *local_sink_pad;
>  	struct v4l2_subdev_route *route;
>  	struct device *dev = sd->dev;
> -	int ret = 0;
> +	unsigned int num_entries = 0;
> +	int ret;
>
>  	lockdep_assert_held(state->lock);
>
>  	if (WARN_ON(!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE)))
>  		return -EINVAL;
>
> +	/* Count the number of entries first */
> +	media_entity_for_each_pad(&sd->entity, local_sink_pad) {
> +		if (!(local_sink_pad->flags & MEDIA_PAD_FL_SINK))
> +			continue;
> +
> +		for_each_active_route(&state->routing, route) {
> +			if (route->source_pad != pad ||
> +			    route->sink_pad != local_sink_pad->index)
> +				continue;
> +
> +			num_entries++;
> +
> +			if (num_entries > V4L2_FRAME_DESC_ENTRY_MAX)
> +				return -E2BIG;
> +		}
> +	}
> +
> +	if (num_entries > V4L2_FRAME_DESC_ENTRY_MAX)
> +		return -E2BIG;
> +
> +	if (num_entries > V4L2_FRAME_DESC_ENTRY_PREALLOC) {
> +		fd->entry = kzalloc_objs(*fd->entry, num_entries, GFP_KERNEL);

nit: Default should be GFP_KERNEL, needn't GFP_KERNEL when call kzalloc_objs()

Reviewed-by: Frank Li <[email protected]>

> +		if (!fd->entry)
> +			return -ENOMEM;
> +
> +		fd->len_entries = num_entries;
> +	}
> +
>  	/* Iterate over sink pads */
>  	media_entity_for_each_pad(&sd->entity, local_sink_pad) {
>  		struct v4l2_mbus_frame_desc source_fd;
> @@ -2594,12 +2623,15 @@ int __v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
>  				if (IS_ERR(remote_source_pad)) {
>  					dev_dbg(dev, "Failed to find remote pad for sink pad %u\n",
>  						local_sink_pad->index);
> -					return PTR_ERR(remote_source_pad);
> +					ret = PTR_ERR(remote_source_pad);
> +					goto err_free;
>  				}
>
>  				remote_sd = media_entity_to_v4l2_subdev(remote_source_pad->entity);
> -				if (!remote_sd)
> -					return -EINVAL;
> +				if (!remote_sd) {
> +					ret = -EINVAL;
> +					goto err_free;
> +				}
>
>  				ret = v4l2_subdev_call(remote_sd, pad,
>  						       get_frame_desc,
> @@ -2609,7 +2641,7 @@ int __v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
>  					dev_err(dev,
>  						"Failed to get frame desc from remote subdev %s\n",
>  						remote_sd->name);
> -					return ret;
> +					goto err_free;
>  				}
>
>  				have_source_fd = true;
> @@ -2620,7 +2652,8 @@ int __v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
>  					dev_err(dev,
>  						"Frame desc type mismatch: %u != %u\n",
>  						fd->type, source_fd.type);
> -					return -EPIPE;
> +					ret = -EPIPE;
> +					goto err_free;
>  				}
>  			}
>
> @@ -2635,12 +2668,14 @@ int __v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
>  				dev_dbg(dev,
>  					"Failed to find stream %u from source frame desc\n",
>  					route->sink_stream);
> -				return -EPIPE;
> +				ret = -EPIPE;
> +				goto err_free;
>  			}
>
> -			if (fd->num_entries >= V4L2_FRAME_DESC_ENTRY_PREALLOC) {
> +			if (fd->num_entries >= fd->len_entries) {
>  				dev_dbg(dev, "Frame desc entry limit reached\n");
> -				return -E2BIG;
> +				ret = -E2BIG;
> +				goto err_free;
>  			}
>
>  			fd->entry[fd->num_entries] = *source_entry;
> @@ -2652,6 +2687,14 @@ int __v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
>  	}

Is it simpler if

	__free(kfree) *p = kzalloc_objs(*fd->entry, num_entries);

	fd->entry = no_free_ptr(p);
	fd->num_entries =
>
>  	return 0;
> +
> +err_free:
> +	kfree(fd->entry);
> +	fd->entry = fd->entry_mem;
> +	fd->num_entries = 0;
> +	fd->len_entries = V4L2_FRAME_DESC_ENTRY_PREALLOC;
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(__v4l2_subdev_get_frame_desc_passthrough);
>
> --
> 2.47.3
>