linux-kernel - Re: [RFC] i2c: designware: Avoid initcall and initialize the driver like a regular one

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Message-ID: <CABxpGwDMY7T1OuHmLU4EmuBAyE_SCS-GTa=EeSGjZ976N1K9-g@mail.gmail.com>
Date:	Tue, 23 Dec 2014 09:53:20 -0300
From:	Walter Lozano <walter@...guardiasur.com.ar>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	mika.westerberg@...ux.intel.com, Romain.Baeriswyl@...lis.com,
	atull@...nsource.altera.com, raymond.tan@...el.com,
	carlpeng008@...il.com, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] i2c: designware: Avoid initcall and initialize the driver
 like a regular one

On Mon, Dec 22, 2014 at 4:02 PM, Wolfram Sang <wsa@...-dreams.de> wrote:
> On Mon, Dec 22, 2014 at 03:15:49PM -0300, Walter Lozano wrote:
>> Currently, the driver is relying on a subsys_initcall() to register
>> the platform driver struct. This is typically done to allow early uses
>> of the I2C bus (for instance, I2C regulators used from early machine code).
>>
>> While this might work on some cases, it breaks on others. For instance,
>> I2C devices with GPIO-wired interrupts will fail to request the
>> interrupt because of this initcall usage.
>>
>> This commits attempts to fix the above issue, by converting the I2C
>> driver into a regular kernel platform driver. This guarantees it will
>> probe after GPIOs drivers.
>>
>> Platforms based on devicetree won't be affected by this change.
>
> Huh, why is that?
>
>> Legacy platforms, relying on the I2C being available early, might need
>> to implement proper defered mechanisms to overcome potential problems.
>
> NAK. We can't say "Let's cause a regression to force people to fix
> things that used to work" IMO. You exactly pointed out the problem that using
> subsys_initcall() creates.
>
> What about fixing the drivers you use to support deferred probing when
> acquitin the irq?

Yes, probably it is the best approach to avoid possible issues with
other drivers.
I'll check your suggestion.

Thanks for your comments.

Regards,

Walter

-- 
Walter Lozano, VanguardiaSur
www.vanguardiasur.com.ar
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