diff mbox

i2c_powermac: Kernel access of bad area

Message ID 20100106173745.57207520@hyperion.delvare (mailing list archive)
State Accepted, archived
Commit 33a470f6d5e1879c26f16f6b34dc09f82d44f6e9
Headers show

Commit Message

Jean Delvare Jan. 6, 2010, 4:37 p.m. UTC 
Hi Christian, hi Ben,

On Tue, 29 Dec 2009 20:34:15 +1100, Benjamin Herrenschmidt wrote:
> On Mon, 2009-12-28 at 20:40 -0800, Christian Kujau wrote:
> > Hi there,
> > 
> > I was trying to find out if I still need i2c_powermac to get details off 
> > /sys/devices/temperatures, since lm-sensors isn't working for me anyway.

This is because the macintosh/therm_adt746x driver doesn't follow the
standard hwmon sysfs interface. I would love to see that change.

> > After unloading this module, I noticed that reading certain objects would 
> > fail with a segfault on the prompt and an Oops in the kernel log:
> 
> Definitely looks like we fail to clean things up on remove.

Indeed.

> I don't have much time to look into this right now, so best is you file
> a bug report on bugzilla.kernel.org, make sure I'm CCed.
> 
> Jean (added on CC), in case you already know what's up, please share :-)

I don't know anything about this for now. But I'll help if I can.

Christian, did you happen to try removing the i2c-powermac driver
before? I am curious if this is a recent problem, possibly caused by
changes to the i2c stack, or if older kernels already had this problem
and nobody ever noticed. I suspect the latter.

Looking at drivers/macintosh/therm_adt746x.c, the sysfs files are
created in thermostat_init() and removed in thermostat_exit(), which
are the driver's init and exit functions. These files are backed-up by
a per-device structure, so it looks like the wrong thing to do. I think
this is the problem: the sysfs files have a lifetime longer than the
data structure that is backing it up. This is somewhat different from
"we fail to clean things up on remove": I suspect that even if
i2c-powermac was never ever loaded, the same problem would happen.

I think that sysfs files creation should be moved to the end of
probe_thermostat() and sysfs files removal should be moved to the
beginning of remove_thermostat(). Something like the totally untested
patch below (no ppc machine at hand):

---
 drivers/macintosh/therm_adt746x.c |   34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

Comments

Christian Kujau Jan. 6, 2010, 7:14 p.m. UTC | #1 
On Wed, 6 Jan 2010 at 17:37, Jean Delvare wrote:
> Christian, did you happen to try removing the i2c-powermac driver
> before?

Well, I definitely removed the driver before, but I'm not sure if I ever 
read the /sys files after doing this :-\

> I am curious if this is a recent problem, possibly caused by
> changes to the i2c stack, or if older kernels already had this problem
> and nobody ever noticed. I suspect the latter.

Fair question, but I really could't tell. I realize a bisection would be 
helpful, but I don't think I'll have to time to do this on this machine 
(it's a PowerBook G4, but kernel still compilation usually takes ~30min) 
and I'm not sure that I care _that_ much about this particular issue. 
I just wanted to report this one, for the sake of the archives, as noone 
else seems to be bothered by it anyway...

> I think that sysfs files creation should be moved to the end of
> probe_thermostat() and sysfs files removal should be moved to the
> beginning of remove_thermostat(). Something like the totally untested
> patch below (no ppc machine at hand):

OK, thanks Jean - I'll give it a try later today and let you know.


Thanks again,
Christian.
Christian Kujau Jan. 7, 2010, 3:41 a.m. UTC | #2 
Hi Jean,

On Wed, 6 Jan 2010 at 17:37, Jean Delvare wrote:
> I think that sysfs files creation should be moved to the end of
> probe_thermostat() and sysfs files removal should be moved to the
> beginning of remove_thermostat(). Something like the totally untested
> patch below (no ppc machine at hand):

I applied your patch to 2.6.33-rc3, and was able to unload i2c-powermac and 
then reading the files left in /sys/devices/temperatures. I even tried to 
read the non-existant files (e.g. sensor1_fan_speed, etc...), but the 
kernel just wouldn't oops :)

So the initial oops is gone - yeah!

However, the "Badness" remains when I try to modprobe i2c-powermac again:

[  442.148222] PowerMac i2c bus pmu 2 registered
[  442.148792] PowerMac i2c bus pmu 1 registered
[  442.149299] PowerMac i2c bus mac-io 0 registered
[  442.163573] adt746x: ADT7467 initializing
[  442.170072] adt746x: Lowering max temperatures from 73, 80, 109 to 67, 47, 67
[  442.176559] PowerMac i2c bus uni-n 1 registered
[  442.227115] sysfs: cannot create duplicate filename '/devices/ams'
[  442.227697] ------------[ cut here ]------------
[  442.228176] Badness at fs/sysfs/dir.c:487
[  442.228642] NIP: c00eb71c LR: c00eb71c CTR: 00000000
[  442.229117] REGS: eea0fa50 TRAP: 0700   Not tainted  (2.6.33-rc3)
[  442.229592] MSR: 00029032 <EE,ME,CE,IR,DR>  CR: 42008444  XER: 00000000
[  442.230151] TASK = eea10000[2821] 'modprobe' THREAD: eea0e000
[  442.230191] GPR00: c00eb71c eea0fb00 eea10000 0000004c 000064c6 ffffffff ffffffff 00000000 
[  442.230758] GPR08: efa71740 c03e0000 00000000 000064c6 44008428 10020390 100e0000 100df49c 
[  442.231326] GPR16: 100b54c0 100df49c 100ddd20 1018fb08 100b5340 c03e674c c03e6720 c03ea044 
[  442.231902] GPR24: 00000000 24008422 ffffffea eea0fb58 ef0e9000 ef0e9000 ef0a9ea0 ffffffef 
[  442.233187] NIP [c00eb71c] sysfs_add_one+0x94/0xc0
[  442.233695] LR [c00eb71c] sysfs_add_one+0x94/0xc0
[  442.234363] Call Trace:

I've put the whole dmesg on:

   http://nerdbynature.de/bits/2.6.33-rc2/i2c_powermac/r1/

Thanks for your time,
Christian.
Jean Delvare Jan. 29, 2010, 8:18 a.m. UTC | #3 
Ben, Christian,

On Thu, 7 Jan 2010 17:17:38 +0100, Jean Delvare wrote:
> On Wed, 6 Jan 2010 19:41:05 -0800 (PST), Christian Kujau wrote:
> > Hi Jean,
> > 
> > On Wed, 6 Jan 2010 at 17:37, Jean Delvare wrote:
> > > I think that sysfs files creation should be moved to the end of
> > > probe_thermostat() and sysfs files removal should be moved to the
> > > beginning of remove_thermostat(). Something like the totally untested
> > > patch below (no ppc machine at hand):
> > 
> > I applied your patch to 2.6.33-rc3, and was able to unload i2c-powermac and 
> > then reading the files left in /sys/devices/temperatures. I even tried to 
> > read the non-existant files (e.g. sensor1_fan_speed, etc...), but the 
> > kernel just wouldn't oops :)
> > 
> > So the initial oops is gone - yeah!

Ben, what about applying this patch of mine, as Christian reported it
fixed his oops?

> > However, the "Badness" remains when I try to modprobe i2c-powermac again:
> > 
> > [  442.148222] PowerMac i2c bus pmu 2 registered
> > [  442.148792] PowerMac i2c bus pmu 1 registered
> > [  442.149299] PowerMac i2c bus mac-io 0 registered
> > [  442.163573] adt746x: ADT7467 initializing
> > [  442.170072] adt746x: Lowering max temperatures from 73, 80, 109 to 67, 47, 67
> > [  442.176559] PowerMac i2c bus uni-n 1 registered
> > [  442.227115] sysfs: cannot create duplicate filename '/devices/ams'
> > [  442.227697] ------------[ cut here ]------------
> > [  442.228176] Badness at fs/sysfs/dir.c:487
> > [  442.228642] NIP: c00eb71c LR: c00eb71c CTR: 00000000
> > [  442.229117] REGS: eea0fa50 TRAP: 0700   Not tainted  (2.6.33-rc3)
> > [  442.229592] MSR: 00029032 <EE,ME,CE,IR,DR>  CR: 42008444  XER: 00000000
> > [  442.230151] TASK = eea10000[2821] 'modprobe' THREAD: eea0e000
> > [  442.230191] GPR00: c00eb71c eea0fb00 eea10000 0000004c 000064c6 ffffffff ffffffff 00000000 
> > [  442.230758] GPR08: efa71740 c03e0000 00000000 000064c6 44008428 10020390 100e0000 100df49c 
> > [  442.231326] GPR16: 100b54c0 100df49c 100ddd20 1018fb08 100b5340 c03e674c c03e6720 c03ea044 
> > [  442.231902] GPR24: 00000000 24008422 ffffffea eea0fb58 ef0e9000 ef0e9000 ef0a9ea0 ffffffef 
> > [  442.233187] NIP [c00eb71c] sysfs_add_one+0x94/0xc0
> > [  442.233695] LR [c00eb71c] sysfs_add_one+0x94/0xc0
> > [  442.234363] Call Trace:
> > 
> > I've put the whole dmesg on:
> > 
> >    http://nerdbynature.de/bits/2.6.33-rc2/i2c_powermac/r1/
> 
> Hmm. Looks like a different but somewhat similar problem in the ams
> driver: some code that is in ams_exit() (the module exit code) should
> instead be called when the device (not module) is removed. It probably
> doesn't make much of a difference in the PMU case, but in the I2C case
> it does matter.
> 
> The following, totally untested patch may fix it. I make no guarantee
> that my code isn't racy though, I'm not familiar enough with the ams
> driver code to tell for sure.
> 
> ---
>  drivers/hwmon/ams/ams-core.c |   11 +++++++----
>  drivers/hwmon/ams/ams-i2c.c  |    2 ++
>  drivers/hwmon/ams/ams-pmu.c  |    2 ++
>  drivers/hwmon/ams/ams.h      |    1 +
>  4 files changed, 12 insertions(+), 4 deletions(-)
> 
> --- linux-2.6.33-rc3.orig/drivers/hwmon/ams/ams-core.c	2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.33-rc3/drivers/hwmon/ams/ams-core.c	2010-01-07 17:14:25.000000000 +0100
> @@ -213,7 +213,7 @@ int __init ams_init(void)
>  	return -ENODEV;
>  }
>  
> -void ams_exit(void)
> +void ams_sensor_detach(void)
>  {
>  	/* Remove input device */
>  	ams_input_exit();
> @@ -221,9 +221,6 @@ void ams_exit(void)
>  	/* Remove attributes */
>  	device_remove_file(&ams_info.of_dev->dev, &dev_attr_current);
>  
> -	/* Shut down implementation */
> -	ams_info.exit();
> -
>  	/* Flush interrupt worker
>  	 *
>  	 * We do this after ams_info.exit(), because an interrupt might
> @@ -239,6 +236,12 @@ void ams_exit(void)
>  	pmf_unregister_irq_client(&ams_freefall_client);
>  }
>  
> +static void __exit ams_exit(void)
> +{
> +	/* Shut down implementation */
> +	ams_info.exit();
> +}
> +
>  MODULE_AUTHOR("Stelian Pop, Michael Hanselmann");
>  MODULE_DESCRIPTION("Apple Motion Sensor driver");
>  MODULE_LICENSE("GPL");
> --- linux-2.6.33-rc3.orig/drivers/hwmon/ams/ams-i2c.c	2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.33-rc3/drivers/hwmon/ams/ams-i2c.c	2010-01-07 17:12:46.000000000 +0100
> @@ -238,6 +238,8 @@ static int ams_i2c_probe(struct i2c_clie
>  static int ams_i2c_remove(struct i2c_client *client)
>  {
>  	if (ams_info.has_device) {
> +		ams_sensor_detach();
> +
>  		/* Disable interrupts */
>  		ams_i2c_set_irq(AMS_IRQ_ALL, 0);
>  
> --- linux-2.6.33-rc3.orig/drivers/hwmon/ams/ams-pmu.c	2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.33-rc3/drivers/hwmon/ams/ams-pmu.c	2010-01-07 17:13:47.000000000 +0100
> @@ -133,6 +133,8 @@ static void ams_pmu_get_xyz(s8 *x, s8 *y
>  
>  static void ams_pmu_exit(void)
>  {
> +	ams_sensor_detach();
> +
>  	/* Disable interrupts */
>  	ams_pmu_set_irq(AMS_IRQ_ALL, 0);
>  
> --- linux-2.6.33-rc3.orig/drivers/hwmon/ams/ams.h	2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.33-rc3/drivers/hwmon/ams/ams.h	2010-01-07 17:11:43.000000000 +0100
> @@ -61,6 +61,7 @@ extern struct ams ams_info;
>  
>  extern void ams_sensors(s8 *x, s8 *y, s8 *z);
>  extern int ams_sensor_attach(void);
> +extern void ams_sensor_detach(void);
>  
>  extern int ams_pmu_init(struct device_node *np);
>  extern int ams_i2c_init(struct device_node *np);

Christian, did you ever test this second patch of mine? If you did,
what was the outcome?
Benjamin Herrenschmidt Jan. 29, 2010, 9:34 p.m. UTC | #4 
> Ben, what about applying this patch of mine, as Christian reported it
> fixed his oops?

Sure. I never quite know with i2c which ones you will apply directly and
which ones you want to go through my tree :-)

Hopefully they should still be referened on patchwork, I'll dig there
and pick them up.

Cheers,
Ben.

> > > However, the "Badness" remains when I try to modprobe i2c-powermac again:
> > > 
> > > [  442.148222] PowerMac i2c bus pmu 2 registered
> > > [  442.148792] PowerMac i2c bus pmu 1 registered
> > > [  442.149299] PowerMac i2c bus mac-io 0 registered
> > > [  442.163573] adt746x: ADT7467 initializing
> > > [  442.170072] adt746x: Lowering max temperatures from 73, 80, 109 to 67, 47, 67
> > > [  442.176559] PowerMac i2c bus uni-n 1 registered
> > > [  442.227115] sysfs: cannot create duplicate filename '/devices/ams'
> > > [  442.227697] ------------[ cut here ]------------
> > > [  442.228176] Badness at fs/sysfs/dir.c:487
> > > [  442.228642] NIP: c00eb71c LR: c00eb71c CTR: 00000000
> > > [  442.229117] REGS: eea0fa50 TRAP: 0700   Not tainted  (2.6.33-rc3)
> > > [  442.229592] MSR: 00029032 <EE,ME,CE,IR,DR>  CR: 42008444  XER: 00000000
> > > [  442.230151] TASK = eea10000[2821] 'modprobe' THREAD: eea0e000
> > > [  442.230191] GPR00: c00eb71c eea0fb00 eea10000 0000004c 000064c6 ffffffff ffffffff 00000000 
> > > [  442.230758] GPR08: efa71740 c03e0000 00000000 000064c6 44008428 10020390 100e0000 100df49c 
> > > [  442.231326] GPR16: 100b54c0 100df49c 100ddd20 1018fb08 100b5340 c03e674c c03e6720 c03ea044 
> > > [  442.231902] GPR24: 00000000 24008422 ffffffea eea0fb58 ef0e9000 ef0e9000 ef0a9ea0 ffffffef 
> > > [  442.233187] NIP [c00eb71c] sysfs_add_one+0x94/0xc0
> > > [  442.233695] LR [c00eb71c] sysfs_add_one+0x94/0xc0
> > > [  442.234363] Call Trace:
> > > 
> > > I've put the whole dmesg on:
> > > 
> > >    http://nerdbynature.de/bits/2.6.33-rc2/i2c_powermac/r1/
> > 
> > Hmm. Looks like a different but somewhat similar problem in the ams
> > driver: some code that is in ams_exit() (the module exit code) should
> > instead be called when the device (not module) is removed. It probably
> > doesn't make much of a difference in the PMU case, but in the I2C case
> > it does matter.
> > 
> > The following, totally untested patch may fix it. I make no guarantee
> > that my code isn't racy though, I'm not familiar enough with the ams
> > driver code to tell for sure.
> > 
> > ---
> >  drivers/hwmon/ams/ams-core.c |   11 +++++++----
> >  drivers/hwmon/ams/ams-i2c.c  |    2 ++
> >  drivers/hwmon/ams/ams-pmu.c  |    2 ++
> >  drivers/hwmon/ams/ams.h      |    1 +
> >  4 files changed, 12 insertions(+), 4 deletions(-)
> > 
> > --- linux-2.6.33-rc3.orig/drivers/hwmon/ams/ams-core.c	2009-06-10 05:05:27.000000000 +0200
> > +++ linux-2.6.33-rc3/drivers/hwmon/ams/ams-core.c	2010-01-07 17:14:25.000000000 +0100
> > @@ -213,7 +213,7 @@ int __init ams_init(void)
> >  	return -ENODEV;
> >  }
> >  
> > -void ams_exit(void)
> > +void ams_sensor_detach(void)
> >  {
> >  	/* Remove input device */
> >  	ams_input_exit();
> > @@ -221,9 +221,6 @@ void ams_exit(void)
> >  	/* Remove attributes */
> >  	device_remove_file(&ams_info.of_dev->dev, &dev_attr_current);
> >  
> > -	/* Shut down implementation */
> > -	ams_info.exit();
> > -
> >  	/* Flush interrupt worker
> >  	 *
> >  	 * We do this after ams_info.exit(), because an interrupt might
> > @@ -239,6 +236,12 @@ void ams_exit(void)
> >  	pmf_unregister_irq_client(&ams_freefall_client);
> >  }
> >  
> > +static void __exit ams_exit(void)
> > +{
> > +	/* Shut down implementation */
> > +	ams_info.exit();
> > +}
> > +
> >  MODULE_AUTHOR("Stelian Pop, Michael Hanselmann");
> >  MODULE_DESCRIPTION("Apple Motion Sensor driver");
> >  MODULE_LICENSE("GPL");
> > --- linux-2.6.33-rc3.orig/drivers/hwmon/ams/ams-i2c.c	2009-06-10 05:05:27.000000000 +0200
> > +++ linux-2.6.33-rc3/drivers/hwmon/ams/ams-i2c.c	2010-01-07 17:12:46.000000000 +0100
> > @@ -238,6 +238,8 @@ static int ams_i2c_probe(struct i2c_clie
> >  static int ams_i2c_remove(struct i2c_client *client)
> >  {
> >  	if (ams_info.has_device) {
> > +		ams_sensor_detach();
> > +
> >  		/* Disable interrupts */
> >  		ams_i2c_set_irq(AMS_IRQ_ALL, 0);
> >  
> > --- linux-2.6.33-rc3.orig/drivers/hwmon/ams/ams-pmu.c	2009-06-10 05:05:27.000000000 +0200
> > +++ linux-2.6.33-rc3/drivers/hwmon/ams/ams-pmu.c	2010-01-07 17:13:47.000000000 +0100
> > @@ -133,6 +133,8 @@ static void ams_pmu_get_xyz(s8 *x, s8 *y
> >  
> >  static void ams_pmu_exit(void)
> >  {
> > +	ams_sensor_detach();
> > +
> >  	/* Disable interrupts */
> >  	ams_pmu_set_irq(AMS_IRQ_ALL, 0);
> >  
> > --- linux-2.6.33-rc3.orig/drivers/hwmon/ams/ams.h	2009-06-10 05:05:27.000000000 +0200
> > +++ linux-2.6.33-rc3/drivers/hwmon/ams/ams.h	2010-01-07 17:11:43.000000000 +0100
> > @@ -61,6 +61,7 @@ extern struct ams ams_info;
> >  
> >  extern void ams_sensors(s8 *x, s8 *y, s8 *z);
> >  extern int ams_sensor_attach(void);
> > +extern void ams_sensor_detach(void);
> >  
> >  extern int ams_pmu_init(struct device_node *np);
> >  extern int ams_i2c_init(struct device_node *np);
> 
> Christian, did you ever test this second patch of mine? If you did,
> what was the outcome?
>
Christian Kujau Jan. 30, 2010, 6:03 a.m. UTC | #5 
On Fri, 29 Jan 2010 at 09:18, Jean Delvare wrote:
> Christian, did you ever test this second patch of mine? If you did,
> what was the outcome?

Sorry, I must've missed that 2nd patch of yours. I'll test this now and 
report back.

Thanks,
Christian.
Jean Delvare Jan. 30, 2010, 9:35 a.m. UTC | #6 
On Sat, 30 Jan 2010 08:34:55 +1100, Benjamin Herrenschmidt wrote:
> 
> > Ben, what about applying this patch of mine, as Christian reported it
> > fixed his oops?
> 
> Sure. I never quite know with i2c which ones you will apply directly and
> which ones you want to go through my tree :-)
> 
> Hopefully they should still be referened on patchwork, I'll dig there
> and pick them up.

Well, basically I pick patches that touch drivers/i2c/*, and I don't
pick patches that touch drivers/macintosh/*. When I can't build the
drivers, I don't really feel like pushing the patches myself.
Christian Kujau Jan. 31, 2010, 6:05 a.m. UTC | #7 
On Fri, 29 Jan 2010 at 22:03, Christian Kujau wrote:
> On Fri, 29 Jan 2010 at 09:18, Jean Delvare wrote:
> > Christian, did you ever test this second patch of mine? If you did,
> > what was the outcome?

OK, I've now applied both the drivers/hwmon/ams/ patches and your earlier 
one for drivers/macintosh/therm_adt746x.c [0] to a current -git checkout 
and now I can unload i2c_powermac, list and read the remaining files in
/sys/devices/temperatures, load i2c_powermac again, and unload, and
load, and ... - it's wonderful! :-) No oopses so far.

Feel free to add a Tested-by: Christian Kujau <lists@nerdbynature.de>
so that the patches can be pushed into mainline.

Thanks for the fixes, Jean!

Christian.

[0] http://nerdbynature.de/bits/2.6.33-rc2/i2c_powermac/r2/
Jean Delvare Jan. 31, 2010, 9:52 a.m. UTC | #8 
On Sat, 30 Jan 2010 22:05:26 -0800 (PST), Christian Kujau wrote:
> OK, I've now applied both the drivers/hwmon/ams/ patches and your earlier 
> one for drivers/macintosh/therm_adt746x.c [0] to a current -git checkout 
> and now I can unload i2c_powermac, list and read the remaining files in
> /sys/devices/temperatures, load i2c_powermac again, and unload, and
> load, and ... - it's wonderful! :-) No oopses so far.
> 
> Feel free to add a Tested-by: Christian Kujau <lists@nerdbynature.de>
> so that the patches can be pushed into mainline.

Thanks, I'll resend both patches with proper comments and headers now.

> Thanks for the fixes, Jean!

You're welcome.
diff mbox

Patch

--- linux-2.6.33-rc3.orig/drivers/macintosh/therm_adt746x.c	2010-01-06 17:30:48.000000000 +0100
+++ linux-2.6.33-rc3/drivers/macintosh/therm_adt746x.c	2010-01-06 17:36:35.000000000 +0100
@@ -90,6 +90,8 @@  static struct task_struct *thread_therm
 
 static void write_both_fan_speed(struct thermostat *th, int speed);
 static void write_fan_speed(struct thermostat *th, int speed, int fan);
+static void thermostat_create_files(void);
+static void thermostat_remove_files(void);
 
 static int
 write_reg(struct thermostat* th, int reg, u8 data)
@@ -161,6 +163,8 @@  remove_thermostat(struct i2c_client *cli
 	struct thermostat *th = i2c_get_clientdata(client);
 	int i;
 	
+	thermostat_remove_files();
+
 	if (thread_therm != NULL) {
 		kthread_stop(thread_therm);
 	}
@@ -449,6 +453,8 @@  static int probe_thermostat(struct i2c_c
 		return -ENOMEM;
 	}
 
+	thermostat_create_files();
+
 	return 0;
 }
 
@@ -566,7 +572,6 @@  thermostat_init(void)
 	struct device_node* np;
 	const u32 *prop;
 	int i = 0, offset = 0;
-	int err;
 
 	np = of_find_node_by_name(NULL, "fan");
 	if (!np)
@@ -633,6 +638,17 @@  thermostat_init(void)
 		return -ENODEV;
 	}
 
+#ifndef CONFIG_I2C_POWERMAC
+	request_module("i2c-powermac");
+#endif
+
+	return i2c_add_driver(&thermostat_driver);
+}
+
+static void thermostat_create_files(void)
+{
+	int err;
+
 	err = device_create_file(&of_dev->dev, &dev_attr_sensor1_temperature);
 	err |= device_create_file(&of_dev->dev, &dev_attr_sensor2_temperature);
 	err |= device_create_file(&of_dev->dev, &dev_attr_sensor1_limit);
@@ -647,16 +663,9 @@  thermostat_init(void)
 	if (err)
 		printk(KERN_WARNING
 			"Failed to create tempertaure attribute file(s).\n");
-
-#ifndef CONFIG_I2C_POWERMAC
-	request_module("i2c-powermac");
-#endif
-
-	return i2c_add_driver(&thermostat_driver);
 }
 
-static void __exit
-thermostat_exit(void)
+static void thermostat_remove_files(void)
 {
 	if (of_dev) {
 		device_remove_file(&of_dev->dev, &dev_attr_sensor1_temperature);
@@ -673,9 +682,14 @@  thermostat_exit(void)
 			device_remove_file(&of_dev->dev,
 					   &dev_attr_sensor2_fan_speed);
 
-		of_device_unregister(of_dev);
 	}
+}
+
+static void __exit
+thermostat_exit(void)
+{
 	i2c_del_driver(&thermostat_driver);
+	of_device_unregister(of_dev);
 }
 
 module_init(thermostat_init);