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

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Message-ID: <20130923152427.GX30088@pengutronix.de>
Date:	Mon, 23 Sep 2013 17:24:27 +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 05:20:18PM +0200, Johan Hovold wrote:
> On Mon, Sep 23, 2013 at 04:50:29PM +0200, Sascha Hauer wrote:
> > 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?
> 
> Perhaps that paragraph was a bit unclear: I move them out of __init
> _and_ use platform_driver_register instead of platform_driver_probe as
> well.

Oh yes, I should have looked closer. Sorry for the noise.

Sascha

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