linux-kernel - Re: [PATCHv2 3/3] gpio: msm: Add device tree and irqdomain support for gpio-msm-v2

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Date:	Fri, 31 May 2013 23:01:36 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Rohit Vaswani <rvaswani@...eaurora.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	Russell King <linux@....linux.org.uk>,
	David Brown <davidb@...eaurora.org>,
	Bryan Huntsman <bryanh@...eaurora.org>,
	Linux Documentation List <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCHv2 3/3] gpio: msm: Add device tree and irqdomain support
 for gpio-msm-v2

On Thu, May 23, 2013 at 3:29 AM, Rohit Vaswani <rvaswani@...eaurora.org> wrote:
> This cleans up the gpio-msm-v2 driver of all the global define usage.
> The number of gpios are now defined in the device tree. This enables
> adding irqdomain support as well.

Besides the other comments, I have one important here.

> -static int __init msm_gpio_init(void)
> -{
> -       int rc;
> -
> -       rc = platform_driver_register(&msm_gpio_driver);
> -       if (!rc) {
> -               rc = platform_device_register(&msm_device_gpio);
> -               if (rc)
> -                       platform_driver_unregister(&msm_gpio_driver);
> -       }
> -
> -       return rc;
> -}
> -
> -static void __exit msm_gpio_exit(void)
> -{
> -       platform_device_unregister(&msm_device_gpio);
> -       platform_driver_unregister(&msm_gpio_driver);
> -}
> -
> -postcore_initcall(msm_gpio_init);
> -module_exit(msm_gpio_exit);
> +module_platform_driver(msm_gpio_driver)

It's a really big mistake to do this.
GPIO nowadays is used in many hardware subsystems to support early
stages of booting and initializing.

postcore_initcall is early enough to support mostly anything that
hardware wants from GPIO (for example, ACPI events, though it seems
not a case here).

Please, do not do such changes without good argumets.

--
With Best Regards,
Andy Shevchenko
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