linux-kernel - Re: 2.6.24 breaks BIOS updates on all Dell machines

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Message-ID: <20080205234413.GA9386@suse.de>
Date:	Tue, 5 Feb 2008 15:44:13 -0800
From:	Greg KH <gregkh@...e.de>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	markus.rechberger@....com,
	"Matt_Domsch@...l.com" <Matt_Domsch@...l.com>,
	Jos?? Luis Tall??n <jltallon@...-solutions.net>,
	"Douglas_Warzecha@...l.com" <Douglas_Warzecha@...l.com>,
	"Abhay_Salunke@...l.com" <Abhay_Salunke@...l.com>,
	linux-kernel@...r.kernel.org,
	Michael E Brown <Michael_E_Brown@...l.com>,
	Kay Sievers <kay.sievers@...y.org>
Subject: Re: 2.6.24 breaks BIOS updates on all Dell machines

On Tue, Feb 05, 2008 at 09:16:42PM +0100, Jean Delvare wrote:
> On Mon, 4 Feb 2008 22:45:47 -0800, Greg KH wrote:
> > On Tue, Jan 29, 2008 at 11:15:22PM +0100, Jean Delvare wrote:
> > > I'm a bit confused. It seems to me that the "class devices" are named
> > > differently in recent kernels. The i2c-dev class devices were originally
> > > showing as i2c-%d in their parent device directories (causing the
> > > collision), and now show as i2c-dev:i2c-%d. This suggests that the
> > > collision the patch above was trying to solve is in fact already fixed
> > > (by prefixing the device name with the class name). The good news is
> > > that it would mean that we can just revert the patch in question...
> > > 
> > > But quite frankly I'm not really sure, the class devices look different
> > > on every kernel I looked at, depending on the version and whether
> > > CONFIG_SYSFS_DEPRECATED is set or not.
> > 
> > THe naming is different depending on that sysfs variable, yes.  But it
> > should be consistant other than that.  If not, please let me know.
> > 
> > And yes, we did have to add the ":" a while ago to handle the namespace
> > collisions we were having.
> 
> OK, I am officially confused now.

Heh, it is a mess :)

> This is 2.6.24, CONFIG_SYSFS_DEPRECATED=y:
> 
> # ls -l /sys/class/i2c-adapter/i2c-0
> total 0
> lrwxrwxrwx 1 root root    0 f?v  5 18:07 device -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0
> lrwxrwxrwx 1 root root    0 f?v  5 18:17 i2c-dev:i2c-0 -> ../../../class/i2c-dev/i2c-0
> -r--r--r-- 1 root root 4096 f?v  5 18:07 name
> drwxr-xr-x 2 root root    0 f?v  5 18:17 power
> lrwxrwxrwx 1 root root    0 f?v  5 18:07 subsystem -> ../../../class/i2c-adapter
> -rw-r--r-- 1 root root 4096 f?v  5  2008 uevent
> 
> 2.6.24 rebuilt without CONFIG_SYSFS_DEPRECATED:
> 
> # ls -l /sys/class/i2c-adapter/i2c-0/
> total 0
> lrwxrwxrwx 1 root root    0 f?v  5 18:42 device -> ../../../../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0
> drwxr-xr-x 3 root root    0 f?v  5 18:42 i2c-0
> -r--r--r-- 1 root root 4096 f?v  5 18:31 name
> drwxr-xr-x 2 root root    0 f?v  5 18:42 power
> lrwxrwxrwx 1 root root    0 f?v  5 18:31 subsystem -> ../../../../../../class/i2c-adapter
> -rw-r--r-- 1 root root 4096 f?v  5  2008 uevent
> 
> The latter corresponds to what older kernels had ("i2c-0"). This means
> that enabling CONFIG_SYSFS_DEPRECATED causes the i2c-dev class device
> names to change.

Yes.  Well, no, not really.  The class device names are the same, it's
just that it is a symlink in the DEPRECATED=Y name and a real directory
in the =N case.

> Isn't it supposed to be exactly the other way around, i.e. enabling
> CONFIG_SYSFS_DEPRECATED should preserve the names as they were in
> older kernels?

The real name is the same (look above, it's really called "i2c-0" in
both cases, just that the symlink in the =Y case has to have a different
name to handle the fact that there could be duplicate names in this
format.

Does that help?

It's really to keep older programs still work properly.  The =N case is
what you should pay attention to for all modern distros.

thanks,

greg k-h
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