Re: [PATCH 07/11] media: exynos4-is: Add support for multiple sensors on one port

[Tomasz Figa <tfiga@chromium.org>]

On Sat, Apr 25, 2020 at 07:26:46PM -0700, Jonathan Bakker wrote:
> On some devices, there may be multiple camera sensors attached
> to the same port.  Make sure we probe all of them, not just the
> first one.
> 
> Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
> ---
>  drivers/media/platform/exynos4-is/media-dev.c | 32 ++++++++++++-------
>  1 file changed, 21 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/media/platform/exynos4-is/media-dev.c b/drivers/media/platform/exynos4-is/media-dev.c
> index b38445219c72..a87ebd7913be 100644
> --- a/drivers/media/platform/exynos4-is/media-dev.c
> +++ b/drivers/media/platform/exynos4-is/media-dev.c
> @@ -397,25 +397,28 @@ static void fimc_md_pipelines_free(struct fimc_md *fmd)
>  /* Parse port node and register as a sub-device any sensor specified there. */
>  static int fimc_md_parse_port_node(struct fimc_md *fmd,
>  				   struct device_node *port,
> -				   unsigned int index)
> +				   unsigned int *index)
>  {
> -	struct fimc_source_info *pd = &fmd->sensor[index].pdata;
> +	struct fimc_source_info *pd;
>  	struct device_node *rem, *ep, *np;
> -	struct v4l2_fwnode_endpoint endpoint = { .bus_type = 0 };
> +	struct v4l2_fwnode_endpoint endpoint;
>  	int ret;
>  
> -	/* Assume here a port node can have only one endpoint node. */
>  	ep = of_get_next_child(port, NULL);
>  	if (!ep)
>  		return 0;
>  
> +parse_sensor:
> +	pd = &fmd->sensor[*index].pdata;
> +	endpoint.bus_type = 0;
> +
>  	ret = v4l2_fwnode_endpoint_parse(of_fwnode_handle(ep), &endpoint);
>  	if (ret) {
>  		of_node_put(ep);
>  		return ret;
>  	}
>  
> -	if (WARN_ON(endpoint.base.port == 0) || index >= FIMC_MAX_SENSORS) {
> +	if (WARN_ON(endpoint.base.port == 0) || *index >= FIMC_MAX_SENSORS) {
>  		of_node_put(ep);
>  		return -EINVAL;
>  	}
> @@ -462,16 +465,16 @@ static int fimc_md_parse_port_node(struct fimc_md *fmd,
>  		pd->fimc_bus_type = pd->sensor_bus_type;
>  	of_node_put(np);
>  
> -	if (WARN_ON(index >= ARRAY_SIZE(fmd->sensor))) {
> +	if (WARN_ON(*index >= ARRAY_SIZE(fmd->sensor))) {
>  		of_node_put(rem);
>  		return -EINVAL;
>  	}
>  
> -	fmd->sensor[index].asd.match_type = V4L2_ASYNC_MATCH_FWNODE;
> -	fmd->sensor[index].asd.match.fwnode = of_fwnode_handle(rem);
> +	fmd->sensor[*index].asd.match_type = V4L2_ASYNC_MATCH_FWNODE;
> +	fmd->sensor[*index].asd.match.fwnode = of_fwnode_handle(rem);
>  
>  	ret = v4l2_async_notifier_add_subdev(&fmd->subdev_notifier,
> -					     &fmd->sensor[index].asd);
> +					     &fmd->sensor[*index].asd);
>  	if (ret) {
>  		of_node_put(rem);
>  		return ret;
> @@ -479,6 +482,13 @@ static int fimc_md_parse_port_node(struct fimc_md *fmd,
>  
>  	fmd->num_sensors++;
>  
> +	/* Check for additional sensors on same port */
> +	ep = of_get_next_child(port, ep);
> +	if (ep) {
> +		(*index)++;

Do we need this index argument at all? I can see that we already have
fmd->num_sensors and we increment it every time we discover a sensor.
Perhaps we could just use it instead?

> +		goto parse_sensor;

As we know, goto in principle isn't the best coding pattern. There is a
number of exceptions where it is welcome, e.g. error handling, but
reimplementing a loop using goto is not very nice.

Instead, could you separate the code that probes one sensor into
fimc_md_parse_one_endpoint() and in this one simply iterate over all child
nodes of the port using for_each_child_of_node()?

Best regards,
Tomasz