linux-kernel - Re: [PATCH v3 07/14] software_node: Add support for fwnode

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Message-ID: <d47e0ccf-9def-e9c9-fdfb-390ad5d2ee5e@gmail.com>
Date:   Thu, 24 Dec 2020 14:21:15 +0000
From:   Daniel Scally <djrscally@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        devel@...ica.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Yong Zhi <yong.zhi@...el.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Tian Shu Qiu <tian.shu.qiu@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Erik Kaneda <erik.kaneda@...el.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        kieran.bingham+renesas@...asonboard.com,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Marco Felsch <m.felsch@...gutronix.de>,
        niklas.soderlund+renesas@...natech.se,
        Steve Longerbeam <slongerbeam@...il.com>,
        "Krogerus, Heikki" <heikki.krogerus@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v3 07/14] software_node: Add support for fwnode_graph*()
 family of functions

Hi Andy, Laurent

> On Thu, Dec 24, 2020 at 2:55 PM Laurent Pinchart
> <laurent.pinchart@...asonboard.com> wrote:
>> On Thu, Dec 24, 2020 at 02:24:12PM +0200, Andy Shevchenko wrote:
>>> On Thu, Dec 24, 2020 at 3:14 AM Daniel Scally wrote:
> 
> ...
> 
>>>> +               if (!strncmp(to_swnode(port)->node->name, "port@",
>>>
>>> You may use here corresponding _FMT macro.
>>>
>>>> +                            FWNODE_GRAPH_PORT_NAME_PREFIX_LEN))
>>>> +                       return port;
> 
> ...
> 
>>>> +       /* Ports have naming style "port@n", we need to select the n */
>>>
>>>> +       ret = kstrtou32(swnode->parent->node->name + FWNODE_GRAPH_PORT_NAME_PREFIX_LEN,
>>>
>>> Maybe a temporary variable?
>>>
>>>   unsigned int prefix_len = FWNODE_GRAPH_PORT_NAME_PREFIX_LEN;
>>>   ...
>>>   ret = kstrtou32(swnode->parent->node->name + prefix_len,
>>
>> Honestly I'm wondering if those macros don't hinder readability. I'd
>> rather write
>>
>>         + strlen("port@")
> 
> Works for me, since the compiler optimizes this away to be a plain constant.

Well, how about instead of the LEN macro, we have:

#define FWNODE_GRAPH_PORT_NAME_PREFIX	"port@"
#define FWNODE_GRAPH_PORT_NAME_FMT FWNODE_GRAPH_PORT_NAME_PREFIX "%u"

And then it's still maintainable in one place but (I think) slightly
less clunky, since we can do strlen(FWNODE_GRAPH_PORT_NAME_PREFIX)

Or we can do strlen("port@"), I'm good either way :)