linux-kernel - Re: udev: New default rule for autoloading kernel modules matching CPU modalias

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Message-ID: <59759957.oRusLgSSoH@vostro.rjw.lan>
Date:	Sat, 20 Jul 2013 13:00:12 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Kay Sievers <kay@...y.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	systemd-devel@...ts.freedesktop.org
Subject: Re: udev: New default rule for autoloading kernel modules matching CPU modalias

On Saturday, July 20, 2013 12:56:54 PM Rafael J. Wysocki wrote:
> Hi Kay,
> 
> After a recent change present in 3.11-rc1 there is a driver, called processor,
> that can be bound to the CPU devices whose sysfs directories are located under
> /sys/devices/system/cpu/.  A side effect of this is that, after the driver has
> been bound to those devices, the kernel adds DRIVER=processor to ENV for CPU
> uevents and they don't match the default rule for autoloading modules matching
> MODALIAS:
> 
> DRIVER!="?*", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"
> 
> any more.  However, there are some modules whose module aliases match specific
> CPU features through the modalias string and those modules should be loaded
> automatically if a compatible CPU is present.  Yet, with the processor driver
> bound to the CPU devices the above rule is not sufficient for that, so we need
> a new default udev rule allowing those modules to be autoloaded even if the
> CPU devices have drivers.
> 
> On my test systems I added the following rule for that:
> 
> ACTION="add", SUBSYSTEM=="cpu", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"

That should have been:

ACTION=="add", SUBSYSTEM=="cpu", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"

sorry about the mistake.

> in a separate file, but I'm not a udev expert, so I guess it may be done in a
> better way.
> 
> Can you please consider adding such a rule to the default set of udev rules?

Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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