linux-kernel - Re: [PATCH v1 3/3] v4l: async: Match parent devices

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Date:   Mon, 22 May 2017 17:11:11 +0100
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Kieran Bingham <kbingham@...nel.org>
Cc:     linux-renesas-soc@...r.kernel.org, linux-media@...r.kernel.org,
        sakari.ailus@....fi, niklas.soderlund@...natech.se,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Tuukka Toivonen <tuukka.toivonen@...el.com>,
        Javi Merino <javi.merino@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 3/3] v4l: async: Match parent devices

Hi Laurent,

On 18/05/17 15:01, Laurent Pinchart wrote:
> Hi Kieran,
> 
> Thank you for the patch.
> 
> On Wednesday 17 May 2017 16:03:39 Kieran Bingham wrote:
>> From: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
>>
>> Devices supporting multiple endpoints on a single device node must set
>> their subdevice fwnode to the endpoint to allow distinct comparisons.
>>
>> Adapt the match_fwnode call to compare against the provided fwnodes
>> first, but also to search for a comparison against the parent fwnode.
>>
>> This allows notifiers to pass the endpoint for comparison and still
>> support existing subdevices which store their default parent device
>> node.
>>
>> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
>> ---
>>  drivers/media/v4l2-core/v4l2-async.c | 20 ++++++++++++++++----
>>  1 file changed, 16 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-async.c
>> b/drivers/media/v4l2-core/v4l2-async.c index e1e181db90f7..65735a5c4350
>> 100644
>> --- a/drivers/media/v4l2-core/v4l2-async.c
>> +++ b/drivers/media/v4l2-core/v4l2-async.c
>> @@ -41,14 +41,26 @@ static bool match_devname(struct v4l2_subdev *sd,
>>  	return !strcmp(asd->match.device_name.name, dev_name(sd->dev));
>>  }
>>
> /*
>  * Check whether the two device_node pointers refer to the same OF node. We
>  * can't compare pointers directly as they can differ if overlays have been
>  * applied.
>  */

Thanks - that's a good addition - I've put it in.

> 
>> +static bool match_of(struct device_node *a, struct device_node *b)
>> +{
>> +	return !of_node_cmp(of_node_full_name(a), of_node_full_name(b));
>> +}
>> +
>>  static bool match_fwnode(struct v4l2_subdev *sd, struct v4l2_async_subdev
>> *asd)
>> {
>> +	struct device_node *sdnode;
>> +	struct fwnode_handle *async_device;
> 
> I would name this asd_fwnode, and to be consistent rename sdnode to sd_ofnode.

Actually, now that I agree with Sakari, and the parent of both the SD and the
ASD should be cross-referenced, I have used:

	sd_parent = fwnode_graph_get_port_parent(sd->fwnode);
	asd_parent = fwnode_graph_get_port_parent(asd_fwnode);

> 
>> +
>> +	async_device = fwnode_graph_get_port_parent(asd->match.fwnode.fwnode);
>> +
>>  	if (!is_of_node(sd->fwnode) || !is_of_node(asd->match.fwnode.fwnode))
>> -		return sd->fwnode == asd->match.fwnode.fwnode;
>> +		return sd->fwnode == asd->match.fwnode.fwnode ||
>> +		       sd->fwnode == async_device;
> 
> I wonder whether we could simplify this by changing the 
> fwnode_graph_get_port_parent() API. At the moment the function walks two or 
> three levels up depending on whether there's a ports name or not. If we turned 
> in into a function that accepts an endpoint, port or device node, and returns 
> the device node unconditionally (basically, returning the argument if its name 
> is not "port(@[0-9]+)?" or "endpoint(@[0-9]+)?", and walking up until it 
> reaches the device node otherwise), you could write the above
> 
> 	asd_fwnode = fwnode_graph_get_port_parent(asd->match.fwnode.fwnode);
> 
>   	if (!is_of_node(sd->fwnode) || !is_of_node(asd_fwnode))
> 		       sd->fwnode == asd_fwnode;
> 
> 	sdnode = to_of_node(sd->fwnode);
>  
> 	return match_of(sdnode, to_of_node(asd_node));


I don't think that would help here. I want the function to do comparisons on the
endpoint when provided - I don't want helpers to suddenly bring the comparison
up to the device level.

> 
>> +
>> +	sdnode = to_of_node(sd->fwnode);
>>
>> -	return !of_node_cmp(of_node_full_name(to_of_node(sd->fwnode)),
>> -			    of_node_full_name(
>> -				    to_of_node(asd->match.fwnode.fwnode)));
>> +	return match_of(sdnode, to_of_node(asd->match.fwnode.fwnode)) ||
>> +	       match_of(sdnode, to_of_node(async_device));
> 
> This is getting a bit complex, could you document the function ?

I've added comments, and improved helpers - I think it's looking a lot better now :)

> 
>>  }
>>
>>  static bool match_custom(struct v4l2_subdev *sd, struct v4l2_async_subdev
>> *asd)
> 

--
Kieran