Re: linux-next: Tree for July 30

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Thu, Jul 31, 2008 at 08:48:56PM +0200, Rafael J. Wysocki wrote:
> On Thursday, 31 of July 2008, Dmitry Torokhov wrote:
> > On Thu, Jul 31, 2008 at 10:44:37AM -0700, Andrew Morton wrote:
> > > On Thu, 31 Jul 2008 11:56:48 -0400 Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:
> > > 
> > > > On Thu, Jul 31, 2008 at 05:36:16PM +0200, Bartlomiej Zolnierkiewicz wrote:
> > > > > On Thu, Jul 31, 2008 at 4:07 PM, Dmitry Torokhov
> > > > > <dmitry.torokhov@gmail.com> wrote:
> > > > > > On Wed, Jul 30, 2008 at 11:10:29PM -0700, Andrew Morton wrote:
> > > > > >> On Wed, 30 Jul 2008 17:06:35 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> > > > > >>
> > > > > >> > I have created today's linux-next tree at
> > > > > >> > git://git.kernel.org/pub/scm/linux/kernel/git/sfr/linux-next.git
> > > > > >>
> > > > > >> The X server broke on my FC8 t61p thinkpad.  Mainline is OK.
> > > > > >>
> > > > > >> Various information is at http://userweb.kernel.org/~akpm/mo/
> > > > > >>
> > > > > >> I'm suspecting the input layer - my synaptics device seems to have
> > > > > >> disappeared?  See http://userweb.kernel.org/~akpm/mo/Xorg-log-diff.txt
> > > > > >>
> > > > > >
> > > > > > I think this patch should help with Synaptics:
> > > > > 
> > > > > Which unfortunately doesn't help all people running with older synaptics
> > > > > user-space after commit 0571c5d20aca71c735222132b02aebddf593045c
> > > > > ("Input: expand keycode space").
> > > > > 
> > > > > Can't this be solved without breaking Xorg on newer kernels running
> > > > > older synaptics?
> > > > > 
> > > > 
> > > > No. The X driver is broken. It tells kernel to use buffer bugger than
> > > > allocated and gets its stack smashed. Tslib has also soma funkiness
> > > > in the ioctl handling as well... *shrug*
> > > > 
> > > > We have a couple months to get distros updated...
> > > > 
> > > 
> > > aaarrrrgggggghhh.  I don't think this is practical.  This means that
> > > (for example) FC5 machines (of which I happen to have one) are dead. 
> > > And lots of other older-distro-based systems.
> > > 
> > > Is there some userspace workaround which doesn't require an X server
> > > update?
> > > 
> > > Surely it must be possible to make the kernel contiue to support these
> > > servers?
> > > 
> > 
> > Andrew,
> > 
> > It is not like we broke ABI here. The progam (synaptics driver) had a
> > grave bug. Older kernels happened to paper over the bug because they
> > did not fill the whole buffer that was advertised as available. Now
> > that we have more data to report the bug bit us. What do you want me
> > to do?
> > 
> > Synaptics driver is a small package and takes 2 minutes to recompile.
> > You don't have to update entire X server with it (in fact I don't think
> > it is even part of X distribution because it is GPL).
> 
> Well, we're not supposed to break user space that we used to work with, even
> if it is known to be buggy.

No, I am sorry. We are not supposed to break userspace ABI, but that
is it. Can you vouch that 2.6.25 did not break a single userspace
program out there?

>  Many people use the older user space on their
> test systems which are not practical to upgrade.
> 

I don't understand this - it is expected that everyone jumps and
upgrades their kernels with ease but updating broken userspace
bits is super-hard... Plus, in this case the fixed driver will
happily work with old kernels.

> IOW, if the change responsible for this makes it to the mainline kernel, it
> will be considered as a regression.
> 

Like I said, I don't agree.

-- 
Dmitry