linux-kernel - Re: [PATCH] sunxi-rsb: Include OF based modalias in device uevent

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Message-ID: <2479565.qdx1IVDIGC@pebbles>
Date:   Mon, 27 Nov 2017 18:19:13 +0100
From:   Stefan Brüns <stefan.bruens@...h-aachen.de>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, Rob Herring <robh@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Chen-Yu Tsai <wens@...e.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] sunxi-rsb: Include OF based modalias in device uevent

On Monday, November 27, 2017 4:35:02 PM CET Maxime Ripard wrote:
> Hi,
> 
> On Mon, Nov 27, 2017 at 01:17:25PM +0100, Stefan Brüns wrote:
> > Include the OF-based modalias in the uevent sent when registering devices
> > on the sunxi RSB bus, so that user space has a chance to autoload the
> > kernel module for the device.
> > 
> > Fixes a regression caused by commit 3f241bfa60bd ("arm64: allwinner: a64:
> > pine64: Use dcdc1 regulator for mmc0"). When the axp20x-rsb module for
> > the AXP803 PMIC is built as a module, it is not loaded and the system
> > ends up with an disfunctional MMC controller.
> > 
> > Cc: stable <stable@...r.kernel.org>
> > Signed-off-by: Stefan Brüns <stefan.bruens@...h-aachen.de>
> > ---
> > 
> >  drivers/bus/sunxi-rsb.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/drivers/bus/sunxi-rsb.c b/drivers/bus/sunxi-rsb.c
> > index 328ca93781cf..37cb57244cbe 100644
> > --- a/drivers/bus/sunxi-rsb.c
> > +++ b/drivers/bus/sunxi-rsb.c
> > @@ -173,11 +173,24 @@ static int sunxi_rsb_device_remove(struct device
> > *dev)> 
> >  	return drv->remove(to_sunxi_rsb_device(dev));
> >  
> >  }
> > 
> > +static int sunxi_rsb_device_uevent(struct device *dev,
> > +				   struct kobj_uevent_env *env)
> > +{
> > +	int ret;
> > +
> > +	ret = of_device_uevent_modalias(dev, env);
> > +	if (ret != -ENODEV)
> > +		return ret;
> 
> A comment explaining why we need to ignore the ENODEV error code would
> be great here.

Lazy answer - everyone else is doing the same, and nobody cared to add an 
explanation.

For *some* drivers, this is likely because the same device may be enumerated 
from e.g ACPI or OF, and for an ACPI device -ENODEV will be returned, as
dev->of_node is NULL.

For devices which are only usable in an OF context, this is bogus. Not sure 
about sunxi-rsb.

> > +	return 0;
> > +}
> > +
> > 
> >  static struct bus_type sunxi_rsb_bus = {
> >  
> >  	.name		= RSB_CTRL_NAME,
> >  	.match		= sunxi_rsb_device_match,
> >  	.probe		= sunxi_rsb_device_probe,
> >  	.remove		= sunxi_rsb_device_remove,
> > 
> > +	.uevent		= sunxi_rsb_device_uevent,
> 
> Any reason to not use of_device_uevent_modalias directly here?

*If* sunxi-rsb can be used without OF, then yes, otherwise no.

Regards,

Stefan

-- 
Stefan Brüns  /  Bergstraße 21  /  52062 Aachen
home: +49 241 53809034     mobile: +49 151 50412019
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