linux-kernel - Re: [PATCH] driver/i2c/mux: Add register based mux i2c-mux-reg

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Date:	Thu, 18 Jun 2015 11:04:27 +0200
From:	Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:	ext Paul Bolle <pebolle@...cali.nl>
Cc:	York Sun <yorksun@...escale.com>, wsa@...-dreams.de,
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	Peter Korsgaard <peter.korsgaard@...co.com>
Subject: Re: [PATCH] driver/i2c/mux: Add register based mux i2c-mux-reg

Hi!

On 18/06/15 10:08, ext Paul Bolle wrote:
>>>> You do not see the platform_device, because there are no users yet, put
>>>>> > >> > this MODULE_ALIAS() is perfectly fine, it will allow automatic module loading
>>>>> > >> > in non-DT case.
>>> > > Do you mean that it will allow automatic module loading once the patch
>>> > > that adds a struct platform_device with a "i2c-mux-reg" name lands?
>> > 
>> > Any platform code which will register the platform_device will trigger uevent and
>> > udevd will be able to find the module with this macro. This is a legacy alternative
>> > to device-tree approach.
> That means I've correctly figured out the purpose of this
> MODULE_ALIAS("platform:" stuff. Because it might actually be documented
> somewhere but I managed to not stumble on that documentation.
> 
> With that out of the way: am I right in thinking there's currently no
> platform code that triggers that uevent for
> "MODALIAS=platform:i2c-mux-reg"? Because if there's no struct
> platform_device taking care of that I think this MODULE_ALIAS() should
> not be added, not yet.

Maybe (and hopefully) there will never be a legacy user of this driver. But this macro
is perfectly fine, adds no overhead (but modinfo) and make the module "complete" in a
sense that it supports both types of binding. There is a legacy probe function in it,
all the support for legacy binding with platform_data in it and this modalias is simply
the last part of it.

-- 
Best regards,
Alexander Sverdlin.
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