linux-kernel - Re: [PATCH v1 2/3] device property: Add fwnode_graph_get_port

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Date:   Fri, 19 May 2017 14:34:33 +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,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        John Youn <johnyoun@...opsys.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/3] device property: Add fwnode_graph_get_port_parent

Hi Laurent,

On 18/05/17 14:36, Laurent Pinchart wrote:
> Hi Kieran,
> 
> Thank you for the patch.
> 
> On Wednesday 17 May 2017 16:03:38 Kieran Bingham wrote:
>> From: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
>>
>> V4L2 async notifiers can pass the endpoint fwnode rather than the device
>> fwnode.
> 
> I'm not sure I would mention V4L2 in the commit message, as this is generic.

Good point

>> Provide a helper to obtain the parent device fwnode without first
>> parsing the remote-endpoint as per fwnode_graph_get_remote_port_parent.
>>
>> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
>> ---
>>  drivers/base/property.c  | 25 +++++++++++++++++++++++++
>>  include/linux/property.h |  2 ++
>>  2 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/base/property.c b/drivers/base/property.c
>> index 627ebc9b570d..caf4316fe565 100644
>> --- a/drivers/base/property.c
>> +++ b/drivers/base/property.c
>> @@ -1245,6 +1245,31 @@ fwnode_graph_get_next_endpoint(struct fwnode_handle
>> *fwnode, EXPORT_SYMBOL_GPL(fwnode_graph_get_next_endpoint);
>>
>>  /**
>> + * fwnode_graph_get_port_parent - Return device node of a port endpoint
>> + * @fwnode: Endpoint firmware node pointing of the port
>> + *
>> + * Extracts firmware node of the device the @fwnode belongs to.
> 
> I'm not too familiar with the fwnode API, but I know it's written in C, where 
> functions don't extract something but return a value :-) How about
> 
> Return: the firmware node of the device the @endpoint belongs to.
> 

I'm not averse to the reword - but it is different to the other functions in the
same context:

fwnode_graph_get_remote_endpoint(struct fwnode_handle *fwnode)
 * Extracts firmware node of a remote endpoint the @fwnode points to.

struct fwnode_handle *fwnode_graph_get_remote_port(struct fwnode_handle *fwnode)
 * Extracts firmware node of a remote port the @fwnode points to.

fwnode_graph_get_remote_port_parent(struct fwnode_handle *fwnode)
 * Extracts firmware node of a remote device the @fwnode points to.

Then with this function becoming:

fwnode_graph_get_port_parent(struct fwnode_handle *endpoint)
 * Returns firmware node of the device the @endpoint belongs to.


I guess those could be changed too ...


>> + */
>> +struct fwnode_handle *
>> +fwnode_graph_get_port_parent(struct fwnode_handle *fwnode)
> 
> This is akin to writing (unsigned int integer)

Yes, good point there - I was thinking of the fwnode as an object itself, but
really it's representing the endpoint, and the fwnode is the class type :)

> 
> How about calling the variable endpoint ? That would also make the 
> documentation clearer in my opinion, with "the @fwnode belongs to" replaced 
> with "the @endpoint belongs to".

Agreed

> 
>> +{
>> +	struct fwnode_handle *parent = NULL;
>> +
>> +	if (is_of_node(fwnode)) {
>> +		struct device_node *node;
>> +
>> +		node = of_graph_get_port_parent(to_of_node(fwnode));
>> +		if (node)
>> +			parent = &node->fwnode;
> 
> This part looks good to me, with the above small change,
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

Thanks,

I'll add this if the code doesn't change drastically based on Sakari's suggestion.

> 
>> +	} else if (is_acpi_node(fwnode)) {
>> +		parent = acpi_node_get_parent(fwnode);
> 
> I can't comment on this one though.
> 
>> +	}
>> +
>> +	return parent;
>> +}
>> +EXPORT_SYMBOL_GPL(fwnode_graph_get_port_parent);
>> +
>> +/**
>>   * fwnode_graph_get_remote_port_parent - Return fwnode of a remote device
>>   * @fwnode: Endpoint firmware node pointing to the remote endpoint
>>   *
>> diff --git a/include/linux/property.h b/include/linux/property.h
>> index 2f482616a2f2..624129b86c82 100644
>> --- a/include/linux/property.h
>> +++ b/include/linux/property.h
>> @@ -274,6 +274,8 @@ void *device_get_mac_address(struct device *dev, char
>> *addr, int alen);
>>
>>  struct fwnode_handle *fwnode_graph_get_next_endpoint(
>>  	struct fwnode_handle *fwnode, struct fwnode_handle *prev);
>> +struct fwnode_handle *fwnode_graph_get_port_parent(
>> +	struct fwnode_handle *fwnode);
>>  struct fwnode_handle *fwnode_graph_get_remote_port_parent(
>>  	struct fwnode_handle *fwnode);
>>  struct fwnode_handle *fwnode_graph_get_remote_port(
>