linux-kernel - Re: [PATCH v2] mfd: syscon: Use a unique name with regmap

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Date:   Thu, 30 Jan 2020 11:08:53 -0600
From:   Suman Anna <s-anna@...com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Lee Jones <lee.jones@...aro.org>, Arnd Bergmann <arnd@...db.de>,
        David Lechner <david@...hnology.com>,
        Tony Lindgren <tony@...mide.com>,
        Roger Quadros <rogerq@...com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>
Subject: Re: [PATCH v2] mfd: syscon: Use a unique name with regmap_config

Hi Andy,

On 1/30/20 9:34 AM, Andy Shevchenko wrote:
> On Tue, Jan 28, 2020 at 1:14 AM Suman Anna <s-anna@...com> wrote:
>>
>> The DT node full name is currently being used in regmap_config
>> which in turn is used to create the regmap debugfs directories.
>> This name however is not guaranteed to be unique and the regmap
>> debugfs registration can fail in the cases where the syscon nodes
>> have the same unit-address but are present in different DT node
>> hierarchies. Replace this logic using the syscon reg resource
>> address instead (inspired from logic used while creating platform
>> devices) to ensure a unique name is given for each syscon.
> 
>> -       syscon_config.name = of_node_full_name(np);
>> +       syscon_config.name = kasprintf(GFP_KERNEL, "%pOFn@...x", np,
>> +                                      (u64)res.start);
> 
> Explicit castings in printf() usually tell us that something is not okay.

Yes, I agree in general.

> Yes, for resource_size_t we have %pa.

And that was the first thing I tried when doing v2, before moving away
from it. This is not for a console printf statement, but is rather for
the regmap debugfs name. Using a %pa adds the 0x and leading zeros in
the debugfs name, when compared to the name before this patch. The
typecast retains the current format, and replaces the unit-address
without the leading 0s either. Introducing a local-variable to avoid the
typecast is overkill.

> 
> On top of that, I would rather see %pfwn to avoid modification for
> other fwnode types.

Did you mean %pfwP? That can probably be handled when syscon code is
updated to use fwnode API.

regards
Suman