linux-kernel - Re: i2c vs nVidia [Re: 2.6.21-rc2-mm1]

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Date:	Mon, 5 Mar 2007 16:33:20 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"J.A. =?ISO-8859-1?Q?Magall=F3n" ?= <jamagallon@....com>
Cc:	linux-kernel@...r.kernel.org, Greg KH <greg@...ah.com>,
	Jean Delvare <khali@...ux-fr.org>
Subject: Re: i2c vs nVidia [Re: 2.6.21-rc2-mm1]

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 guess we need to wait and see if someone hits the same problems with an
in-kernel driver.
-
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