Date:	Mon, 5 Mar 2007 16:44:44 -0800
From:	Greg KH <greg@...ah.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"J.A. Magall?n" <jamagallon@....com>, linux-kernel@...r.kernel.org,
	Jean Delvare <khali@...ux-fr.org>
Subject: Re: i2c vs nVidia [Re: 2.6.21-rc2-mm1]

On Mon, Mar 05, 2007 at 04:33:20PM -0800, Andrew Morton wrote:
> On Tue, 6 Mar 2007 01:16:21 +0100
> "J.A. Magall__n" <jamagallon@....com> wrote:
> 
> > On Fri, 2 Mar 2007 03:00:26 -0800, Andrew Morton <akpm@...ux-foundation.org> wrote:
> > 
> > > 
> > > Temporarily at
> > > 
> > >   http://userweb.kernel.org/~akpm/2.6.21-rc2-mm1/
> > > 
> > 
> > More things...
> > 
> > Yes, this is related to nVidia driver. First of all, I'm not asking for help
> > for a broken closed-source driver. I just want Linux to be fool^^^^bullet-proof ;).
> > 
> > As one can expect from a closed-source driver, recent changes in Linux broke it.
> > New nVidia drivers include some i2c sensors. The driver worked till 2.6.20-rc6-mm3.
> > Since then, I can't use them. I have tracked down the problem to i2c.
> > nVidia driver tries to create 3 i2c devices, and I get this:
> > 
> > **WARNING** I2C adapter driver [NVIDIA i2c adapter 0 at 1:00.0] forgot to specify physical device; fix it!
> >  i2c-10: attach_adapter failed (-16) for driver [w83627hf]
> > **WARNING** I2C adapter driver [NVIDIA i2c adapter 1 at 1:00.0] forgot to specify physical device; fix it!
> >  i2c-11: attach_adapter failed (-16) for driver [w83627hf]
> > **WARNING** I2C adapter driver [NVIDIA i2c adapter 2 at 1:00.0] forgot to specify physical device; fix it!
> >  i2c-12: attach_adapter failed (-16) for driver [w83627hf]
> 
> This problem has always been there - there's a patch in -mm which simply
> converts this message from pr_debug() into printk().
> 
> 
> > Two problems arise:
> > - The directories in /sys/class/i2c-adapter/ are created, but trying to ls
> >   its contents oopses:
> > 
> > last sysfs file: class/i2c-adapter/i2c-0/name
> > Modules linked in: nvidia(P) nfsd exportfs lockd nfs_acl sunrpc snd_intel8x0 snd_ens1371 gameport snd_rawmidi snd_ac97_codec w83627hf ac97_bus hwmon_vid snd_pcm hwmon snd_timer i2c_isa snd_page_alloc i2c_i801 snd i2c_dev loop intel_agp agpgart udf e1000 3c59x microcode ohci1394 ieee1394 usblp evdev
> > CPU:    3
> > EIP:    0060:[<c0194b0c>]    Tainted: P       VLI
> > EFLAGS: 00010202   (2.6.20-jam01 #1)
> > EIP is at sysfs_follow_link+0xe6/0x254
> > eax: 00020b36   ebx: f329edd8   ecx: 00000000   edx: f4ab84d8
> > esi: f0df4ee8   edi: 00000100   ebp: 00000002   esp: f4039ea4
> > ds: 007b   es: 007b   fs: 00d8  gs: 0033  ss: 0068
> > Process sensors (pid: 4991, ti=f4038000 task=f7efa540 task.ti=f4038000)
> > Stack: f7ee4338 f4039edc f0ef7000 ffffffea f4ab84d8 00000000 c0387128 00000000
> >        c02f76a0 f329edd8 00000100 bfd2b6fc c0162b12 00000000 00000000 00000000
> >        00000000 00000000 45eb5857 1f6efe56 c2235fc0 00000000 f4039f44 c011c434
> > Call Trace:
> >  [<c0162b12>] generic_readlink+0x27/0x6e
> >  [<c011c434>] timespec_trunc+0x18/0x5d
> >  [<c011ca11>] current_fs_time+0x41/0x50
> >  [<c015f43a>] sys_readlinkat+0x61/0x7a
> >  [<c015f47a>] sys_readlink+0x27/0x2b
> >  [<c01027ee>] sysenter_past_esp+0x5f/0x85
> >  [<c02f0000>] __down_interruptible+0xa2/0x10e
> >  =======================
> > Code: 24 18 b8 00 b2 39 c0 e8 6e ba 15 00 8b 44 24 18 85 c0 0f 84 42 01 00 00 b8 cc ee 37 c0 e8 dd 73 f9 ff 8b 44 24 10 31 ed 83 c5 01 <8b> 40 24 85 c0 75 f6 8b 44 24 18 89 04 24 bb 01 00 00 00 31 f6 
> > EIP: [<c0194b0c>] sysfs_follow_link+0xe6/0x254 SS:ESP 0068:f4039ea4
> > BUG: at lib/kref.c:32 kref_get()
> >  [<c01ec858>] kref_get+0x3d/0x3f
> >  [<c01ebcd6>] kobject_get+0xf/0x13
> >  [<c0194c00>] sysfs_follow_link+0x1da/0x254
> >  [<c0162b12>] generic_readlink+0x27/0x6e
> >  [<c011c434>] timespec_trunc+0x18/0x5d
> >  [<c011ca11>] current_fs_time+0x41/0x50
> >  [<c015f43a>] sys_readlinkat+0x61/0x7a
> >  [<c015f47a>] sys_readlink+0x27/0x2b
> >  [<c01027ee>] sysenter_past_esp+0x5f/0x85
> >  [<c02f0000>] __down_interruptible+0xa2/0x10e
> >  =======================
> > 
> > - As adapters do not get a driver (or what ?), each time you start X, three
> >   new folders are created in /sys/class/i2c-adapter/
> >   For some AGP black magic, the driver is loaded/registered/whatever 2 times
> >   on each X start.
> > 
> > So, after each X start, you get SIX broken dirs in /sys that hang and oops
> > every app that tries to list i2c devices (like Gnome Sensors Applet, so your
> > Gnome login hangs forever....). Just ls /sys/class/i2c-adapter/i2c-*/.
> > It also oopses when removing i2c modules.
> > 
> > No driver should be able to do that to Linux, even if I try lo load a jpeg
> > of my children renamed to .ko....
> 
> I agree.  It's a shame that it takes the nvidia driver to trigger it, but
> if a driver which was previously working now explodes so horridly it
> perhaps does indicate that we broke something in there.  Or at least, we
> became a heck of a lot less forgiving, and we chose to report driver bugs
> in a rather user-unfriendly fashion.

I think this is due to the recent changes by Jean and David that
reworked the driver model for i2c.  By doing so, they fixed all of the
in-kernel drivers.

It's a bit harder for them to fix up all external drivers as well, but
it looks like nvidia just has to do that and it should work just fine.

Although I do agree that the error checking in the i2c core probably
needs to be fixed up so that we don't end up with empty directories like
this that cause problems later.  Jean, any ideas?

thanks,

greg k-h
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