linux-kernel - Re: [PATCH 0/7] driver core: prevent deferred probe with platform_driver

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Message-ID: <20130923145029.GV30088@pengutronix.de>
Date:	Mon, 23 Sep 2013 16:50:29 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Johan Hovold <jhovold@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Grant Likely <grant.likely@...aro.org>,
	Mark Brown <broonie@...aro.org>, linux-kernel@...r.kernel.org,
	linux-mmc@...r.kernel.org, linux-mtd@...ts.infradead.org,
	linux-pcmcia@...ts.infradead.org, linux-usb@...r.kernel.org,
	linux-fbdev@...r.kernel.org
Subject: Re: [PATCH 0/7] driver core: prevent deferred probe with
 platform_driver_probe

On Mon, Sep 23, 2013 at 04:27:25PM +0200, Johan Hovold wrote:
> Deferred probing cannot be used with platform_driver_probe as by the
> time probing is retried either the driver has been unregistered or its
> probe function has been set to platform_drv_probe_fail.
> 
> With commit e9354576 ("gpiolib: Defer failed gpio requests by default")
> the gpio subsystem started returning -EPROBE_DEFER, which in turn
> several platform drivers using platform_driver_probe return to driver
> core. Other subsystems (e.g. regulator) has since started doing the
> same.
> 
> The first patch in this series prevents platform drivers using
> platform_driver_probe from requesting probe deferral while warning that
> it is not supported.
> 
> The remaining patches move six platform-driver probe functions that rely
> on gpio_request out of __init. There are likely other probe functions
> that might return -EPROBE_DEFER and should be moved out of __init as
> well.

As usually when I read this I wonder why platform_driver_probe exists
anyway. The only advantage I can think off is that the probe functions
are in __init and thus can be disposed of later. Now you remove the
__init annotations from these probe functions. Wouldn't it be better to
convert the drivers to regular platform_driver_register instead?

Sascha

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