linux-kernel - Re: [PATCH] platform_driver_register: warn if probe is in .init.text

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Date:	Fri, 19 Jun 2009 16:43:54 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Greg KH <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform_driver_register:  warn if probe is in
	.init.text

Hi Greg,

On Fri, Jun 19, 2009 at 07:11:28AM -0700, Greg KH wrote:
> On Fri, Jun 19, 2009 at 03:42:19PM +0200, Uwe Kleine-König wrote:
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > ---
> >  drivers/base/platform.c |   42 ++++++++++++++++++++++++++++++++++++------
> >  include/linux/kernel.h  |    2 ++
> >  include/linux/module.h  |   12 ++++++++++++
> >  kernel/extable.c        |   12 ++++++++++++
> >  kernel/module.c         |   36 ++++++++++++++++++++++++++++++++++++
> >  5 files changed, 98 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > index 81cb01b..851ba84 100644
> > --- a/drivers/base/platform.c
> > +++ b/drivers/base/platform.c
> > @@ -470,11 +470,7 @@ static void platform_drv_shutdown(struct device *_dev)
> >  	drv->shutdown(dev);
> >  }
> >  
> > -/**
> > - * platform_driver_register
> > - * @drv: platform driver structure
> > - */
> > -int platform_driver_register(struct platform_driver *drv)
> > +static int __platform_driver_register(struct platform_driver *drv)
> >  {
> >  	drv->driver.bus = &platform_bus_type;
> >  	if (drv->probe)
> > @@ -489,6 +485,40 @@ int platform_driver_register(struct platform_driver *drv)
> >  
> >  	return driver_register(&drv->driver);
> >  }
> > +
> > +/**
> > + * platform_driver_register
> > + * @drv: platform driver structure
> > + */
> > +int platform_driver_register(struct platform_driver *drv)
> > +{
> > +	int ret = __platform_driver_register(drv);
> > +
> > +#if defined(CONFIG_HOTPLUG)
> > +	/*
> > +	 * drivers that are registered by platform_driver_register
> > +	 * should not have their probe function in .init.text.  The
> > +	 * reason is that a probe can happen after .init.text is
> > +	 * discarded which then results in an oops.  The alternatives
> > +	 * are using .devinit.text for the probe function or "register"
> > +	 * with platform_driver_probe.
> > +	 */
> 
> That's not true, remember, drivers built into the system, like platform
> ones, can have their probe function in .init.text, as it will be called
> before we discard .init.text, and will never be called again as the
> device will never be "hot added" at any future time.
> 
> So this could trigger a lot of false positives :(
IMHO this is not a false positive.  You can still do

	for f in unbind bind do echo $deviceid > /sys/bus/platform/drivers/$drivername/$f; done

This type of driver should use platform_driver_probe.

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
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