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Subject: Re: [PATCH 07/11] media: exynos4-is: Add support for multiple sensors
 on one port
To:     Tomasz Figa <tfiga@chromium.org>
Cc:     kyungmin.park@samsung.com, s.nawrocki@samsung.com,
        mchehab@kernel.org, kgene@kernel.org, krzk@kernel.org,
        linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200426022650.10355-1-xc-racer2@live.ca>
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 <20200707183655.GG2621465@chromium.org>
From:   Jonathan Bakker <xc-racer2@live.ca>
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Date:   Sat, 11 Jul 2020 09:48:11 -0700
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Hi Tomasz,

On 2020-07-07 11:36 a.m., Tomasz Figa wrote:
> 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()?
> 

That definitely looks doable, thanks for the suggestion.  I'll work on implementing
and testing this.  It should then also be possible to remove the index hack as well.

> Best regards,
> Tomasz
> 

Thanks,
Jonathan