Nokia N900: v4.16-rc4: oops in iio when grepping sysfs

DISCUSSION Pavel Machek 5 participants 7 messages Mar 9, 2018 – Mar 10, 2018 IIO

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Pavel Machek

author

2018-03-09 22:12 UTC #0 lore raw

Hi!

Hmm. Looks like there's a lot of fun to be had with sysfs.

Pavel

pavel at n900:~$ uname -a
Linux n900 4.16.0-rc4-59690-g7f84626-dirty #543 Thu Mar 8 19:53:30 CET 2018 armv7l GNU/Linux

[  306.402496] bq2415x: command Timer reset
[  312.761322] adp1653 2-0030: Read Addr:03 Val:00 ok
[  313.264129] Unable to handle kernel NULL pointer dereference at
virtual address 00000
000
[  313.272308] pgd = 01336620
[  313.275146] [00000000] *pgd=800af831, *pte=00000000, *ppte=00000000
[  313.281463] Internal error: Oops: 80000007 [#1] ARM
[  313.286376] Modules linked in:
[  313.289459] CPU: 0 PID: 3584 Comm: grep Tainted: G        W
4.16.0-rc4-59690-g
7f84626-dirty #543
[  313.298919] Hardware name: Nokia RX-51 board
[  313.303222] PC is at   (null)
[  313.306213] LR is at iio_ev_state_show+0x38/0x54
[  313.310852] pc : [<00000000>]    lr : [<c05d69c0>]    psr: a0000013
[  313.317169] sp : c7b47e70  ip : c087bb24  fp : 00000001
[  313.322418] r10: cb19e000  r9 : c0857220  r8 : 00001000
[  313.327667] r7 : 00000fff  r6 : cb711c80  r5 : cb19e000  r4 :
00000000
[  313.334228] r3 : 00000001  r2 : 00000000  r1 : c087b4dc  r0 :
ce584800
[  313.340789] Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM
Segment none
[  313.347991] Control: 10c5387d  Table: 87bec019  DAC: 00000051
[  313.353759] Process grep (pid: 3584, stack limit = 0xc4e45eab)
[  313.359619] Stack: (0xc7b47e70 to 0xc7b48000)
[  313.364013] 7e60:                                     c05d6988
cb711b00 ce585c00 c0450d68
[  313.471038] [<c05d69c0>] (iio_ev_state_show) from [<c0450d68>]
(dev_attr_show+0x1c/0x4c)
[  313.479187] [<c0450d68>] (dev_attr_show) from [<c023f934>]
(sysfs_kf_seq_show+0x90/0x108)
[  313.487426] [<c023f934>] (sysfs_kf_seq_show) from [<c023e2f8>]
(kernfs_seq_show+0x24/0x28)
[  313.495758] [<c023e2f8>] (kernfs_seq_show) from [<c01fc954>]
(seq_read+0x1dc/0x500)
[  313.503479] [<c01fc954>] (seq_read) from [<c01d9f80>]
(__vfs_read+0x2c/0x120)
[  313.510681] [<c01d9f80>] (__vfs_read) from [<c01da0fc>]
(vfs_read+0x88/0x114)
[  313.517852] [<c01da0fc>] (vfs_read) from [<c01da584>]
(SyS_read+0x40/0x8c)
[  313.524780] [<c01da584>] (SyS_read) from [<c0101000>]
(ret_fast_syscall+0x0/0x54)
[  313.532318] Exception stack(0xc7b47fa8 to 0xc7b47ff0)
[  313.537414] 7fa0:                   00035330 00042000 00000003

00042000 00008000 00008000

Signature · 9 lines

(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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Greg KH

2018-03-09 22:28 UTC #1 lore raw

Quoted 58 lines · Pavel Machek

Hi!

Hmm. Looks like there's a lot of fun to be had with sysfs.

Pavel

pavel at n900:~$ uname -a
Linux n900 4.16.0-rc4-59690-g7f84626-dirty #543 Thu Mar 8 19:53:30 CET 2018 armv7l GNU/Linux

[  306.402496] bq2415x: command Timer reset
[  312.761322] adp1653 2-0030: Read Addr:03 Val:00 ok
[  313.264129] Unable to handle kernel NULL pointer dereference at
virtual address 00000
000
[  313.272308] pgd = 01336620
[  313.275146] [00000000] *pgd=800af831, *pte=00000000, *ppte=00000000
[  313.281463] Internal error: Oops: 80000007 [#1] ARM
[  313.286376] Modules linked in:
[  313.289459] CPU: 0 PID: 3584 Comm: grep Tainted: G        W
4.16.0-rc4-59690-g
7f84626-dirty #543
[  313.298919] Hardware name: Nokia RX-51 board
[  313.303222] PC is at   (null)
[  313.306213] LR is at iio_ev_state_show+0x38/0x54
[  313.310852] pc : [<00000000>]    lr : [<c05d69c0>]    psr: a0000013
[  313.317169] sp : c7b47e70  ip : c087bb24  fp : 00000001
[  313.322418] r10: cb19e000  r9 : c0857220  r8 : 00001000
[  313.327667] r7 : 00000fff  r6 : cb711c80  r5 : cb19e000  r4 :
00000000
[  313.334228] r3 : 00000001  r2 : 00000000  r1 : c087b4dc  r0 :
ce584800
[  313.340789] Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM
Segment none
[  313.347991] Control: 10c5387d  Table: 87bec019  DAC: 00000051
[  313.353759] Process grep (pid: 3584, stack limit = 0xc4e45eab)
[  313.359619] Stack: (0xc7b47e70 to 0xc7b48000)
[  313.364013] 7e60:                                     c05d6988
cb711b00 ce585c00 c0450d68
[  313.471038] [<c05d69c0>] (iio_ev_state_show) from [<c0450d68>]
(dev_attr_show+0x1c/0x4c)
[  313.479187] [<c0450d68>] (dev_attr_show) from [<c023f934>]
(sysfs_kf_seq_show+0x90/0x108)
[  313.487426] [<c023f934>] (sysfs_kf_seq_show) from [<c023e2f8>]
(kernfs_seq_show+0x24/0x28)
[  313.495758] [<c023e2f8>] (kernfs_seq_show) from [<c01fc954>]
(seq_read+0x1dc/0x500)
[  313.503479] [<c01fc954>] (seq_read) from [<c01d9f80>]
(__vfs_read+0x2c/0x120)
[  313.510681] [<c01d9f80>] (__vfs_read) from [<c01da0fc>]
(vfs_read+0x88/0x114)
[  313.517852] [<c01da0fc>] (vfs_read) from [<c01da584>]
(SyS_read+0x40/0x8c)
[  313.524780] [<c01da584>] (SyS_read) from [<c0101000>]
(ret_fast_syscall+0x0/0x54)
[  313.532318] Exception stack(0xc7b47fa8 to 0xc7b47ff0)
[  313.537414] 7fa0:                   00035330 00042000 00000003

Quoted 2 lines

00042000 00008000 00008000

What file are you opening to cause this?

thanks,

greg k-h

Pavel Machek

author

2018-03-09 23:01 UTC #2 lore raw

Hi!

Quoted 57 lines

Quoted 54 lines

Hmm. Looks like there's a lot of fun to be had with sysfs.

pavel at n900:~$ uname -a
Linux n900 4.16.0-rc4-59690-g7f84626-dirty #543 Thu Mar 8 19:53:30 CET 2018 armv7l GNU/Linux

[  306.402496] bq2415x: command Timer reset
[  312.761322] adp1653 2-0030: Read Addr:03 Val:00 ok
[  313.264129] Unable to handle kernel NULL pointer dereference at
virtual address 00000
000
[  313.272308] pgd = 01336620
[  313.275146] [00000000] *pgd=800af831, *pte=00000000, *ppte=00000000
[  313.281463] Internal error: Oops: 80000007 [#1] ARM
[  313.286376] Modules linked in:
[  313.289459] CPU: 0 PID: 3584 Comm: grep Tainted: G        W
4.16.0-rc4-59690-g
7f84626-dirty #543
[  313.298919] Hardware name: Nokia RX-51 board
[  313.303222] PC is at   (null)
[  313.306213] LR is at iio_ev_state_show+0x38/0x54
[  313.310852] pc : [<00000000>]    lr : [<c05d69c0>]    psr: a0000013
[  313.317169] sp : c7b47e70  ip : c087bb24  fp : 00000001
[  313.322418] r10: cb19e000  r9 : c0857220  r8 : 00001000
[  313.327667] r7 : 00000fff  r6 : cb711c80  r5 : cb19e000  r4 :
00000000
[  313.334228] r3 : 00000001  r2 : 00000000  r1 : c087b4dc  r0 :
ce584800
[  313.340789] Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM
Segment none
[  313.347991] Control: 10c5387d  Table: 87bec019  DAC: 00000051
[  313.353759] Process grep (pid: 3584, stack limit = 0xc4e45eab)
[  313.359619] Stack: (0xc7b47e70 to 0xc7b48000)
[  313.364013] 7e60:                                     c05d6988
cb711b00 ce585c00 c0450d68
[  313.471038] [<c05d69c0>] (iio_ev_state_show) from [<c0450d68>]
(dev_attr_show+0x1c/0x4c)
[  313.479187] [<c0450d68>] (dev_attr_show) from [<c023f934>]
(sysfs_kf_seq_show+0x90/0x108)
[  313.487426] [<c023f934>] (sysfs_kf_seq_show) from [<c023e2f8>]
(kernfs_seq_show+0x24/0x28)
[  313.495758] [<c023e2f8>] (kernfs_seq_show) from [<c01fc954>]
(seq_read+0x1dc/0x500)
[  313.503479] [<c01fc954>] (seq_read) from [<c01d9f80>]
(__vfs_read+0x2c/0x120)
[  313.510681] [<c01d9f80>] (__vfs_read) from [<c01da0fc>]
(vfs_read+0x88/0x114)
[  313.517852] [<c01da0fc>] (vfs_read) from [<c01da584>]
(SyS_read+0x40/0x8c)
[  313.524780] [<c01da584>] (SyS_read) from [<c0101000>]
(ret_fast_syscall+0x0/0x54)
[  313.532318] Exception stack(0xc7b47fa8 to 0xc7b47ff0)
[  313.537414] 7fa0:                   00035330 00042000 00000003

Quoted 2 lines

00042000 00008000 00008000

Quoted 1 line

What file are you opening to cause this?

Strace says:

openat(7, "in_intensity_both_thresh_rising_en",

Quoted 1 line

Quoted 1 line
O_RDONLY|O_LARGEFILE|O_NOFOLLOW) = 3

fstat64(3, {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0 ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbe83b714) = -1 ENOTTY

Quoted 1 line

Quoted 1 line
(Inappropriate ioctl for device)

read(3,
Message from syslogd at localhost at Mar 9 23:54:39 ...
kernel:[ 3097.357696] Internal error: Oops: 80000007 [#2] ARM

So that would be:

./devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1/events/in_intensity_both_thresh_rising_en

And indeed, manually cat-ing that file reproduces the problem.

pavel at n900:/sys/devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1$ cat name
tsl2563

I can not find tsl2563 in MAINTAINERS, file is ./drivers/iio/light/tsl2563.c . I added few people pointed by git log.

Best regards,
Pavel

Signature · 9 lines

(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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Akinobu Mita

2018-03-10 11:19 UTC #3 lore raw

2018-03-10 8:01 GMT+09:00 Pavel Machek <[email protected]>:

Quoted 72 lines

Hi!

Quoted 57 lines

Quoted 54 lines

Hmm. Looks like there's a lot of fun to be had with sysfs.

pavel at n900:~$ uname -a
Linux n900 4.16.0-rc4-59690-g7f84626-dirty #543 Thu Mar 8 19:53:30 CET 2018 armv7l GNU/Linux

[  306.402496] bq2415x: command Timer reset
[  312.761322] adp1653 2-0030: Read Addr:03 Val:00 ok
[  313.264129] Unable to handle kernel NULL pointer dereference at
virtual address 00000
000
[  313.272308] pgd = 01336620
[  313.275146] [00000000] *pgd=800af831, *pte=00000000, *ppte=00000000
[  313.281463] Internal error: Oops: 80000007 [#1] ARM
[  313.286376] Modules linked in:
[  313.289459] CPU: 0 PID: 3584 Comm: grep Tainted: G        W
4.16.0-rc4-59690-g
7f84626-dirty #543
[  313.298919] Hardware name: Nokia RX-51 board
[  313.303222] PC is at   (null)
[  313.306213] LR is at iio_ev_state_show+0x38/0x54
[  313.310852] pc : [<00000000>]    lr : [<c05d69c0>]    psr: a0000013
[  313.317169] sp : c7b47e70  ip : c087bb24  fp : 00000001
[  313.322418] r10: cb19e000  r9 : c0857220  r8 : 00001000
[  313.327667] r7 : 00000fff  r6 : cb711c80  r5 : cb19e000  r4 :
00000000
[  313.334228] r3 : 00000001  r2 : 00000000  r1 : c087b4dc  r0 :
ce584800
[  313.340789] Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM
Segment none
[  313.347991] Control: 10c5387d  Table: 87bec019  DAC: 00000051
[  313.353759] Process grep (pid: 3584, stack limit = 0xc4e45eab)
[  313.359619] Stack: (0xc7b47e70 to 0xc7b48000)
[  313.364013] 7e60:                                     c05d6988
cb711b00 ce585c00 c0450d68
[  313.471038] [<c05d69c0>] (iio_ev_state_show) from [<c0450d68>]
(dev_attr_show+0x1c/0x4c)
[  313.479187] [<c0450d68>] (dev_attr_show) from [<c023f934>]
(sysfs_kf_seq_show+0x90/0x108)
[  313.487426] [<c023f934>] (sysfs_kf_seq_show) from [<c023e2f8>]
(kernfs_seq_show+0x24/0x28)
[  313.495758] [<c023e2f8>] (kernfs_seq_show) from [<c01fc954>]
(seq_read+0x1dc/0x500)
[  313.503479] [<c01fc954>] (seq_read) from [<c01d9f80>]
(__vfs_read+0x2c/0x120)
[  313.510681] [<c01d9f80>] (__vfs_read) from [<c01da0fc>]
(vfs_read+0x88/0x114)
[  313.517852] [<c01da0fc>] (vfs_read) from [<c01da584>]
(SyS_read+0x40/0x8c)
[  313.524780] [<c01da584>] (SyS_read) from [<c0101000>]
(ret_fast_syscall+0x0/0x54)
[  313.532318] Exception stack(0xc7b47fa8 to 0xc7b47ff0)
[  313.537414] 7fa0:                   00035330 00042000 00000003

Quoted 2 lines

00042000 00008000 00008000

Quoted 1 line

What file are you opening to cause this?

Strace says:

openat(7, "in_intensity_both_thresh_rising_en",

Quoted 1 line

Quoted 1 line
O_RDONLY|O_LARGEFILE|O_NOFOLLOW) = 3

fstat64(3, {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0 ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbe83b714) = -1 ENOTTY

Quoted 1 line

Quoted 1 line
(Inappropriate ioctl for device)

read(3,
Message from syslogd at localhost at Mar 9 23:54:39 ...
kernel:[ 3097.357696] Internal error: Oops: 80000007 [#2] ARM

Quoted 5 lines

So that would be:
./devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1/events/in_intensity_both_thresh_rising_en
And indeed, manually cat-ing that file reproduces the problem.

This problem happens when no irq is defined for this device.

In this case, tsl2563_info_no_irq whose read_event_config field is NULL is selected as iio_info. On the other hand, iio_chan_spec for this driver always registers event_spec.

So sysfs files related to the channel events are always created even if no irq is defined.

I think we can fix this issue by defining another iio_chan_spec with no event_spec for no irq case.

Jonathan, do you have any other idea how to fix this issue?

Lars-Peter Clausen

2018-03-10 11:19 UTC #4 lore raw

In reply to Pavel Machek

On 03/10/2018 12:01 AM, Pavel Machek wrote:
[...]

Quoted 17 lines

Quoted 1 line
What file are you opening to cause this?
Strace says:
openat(7, "in_intensity_both_thresh_rising_en",
Quoted 1 line
Quoted 1 line
O_RDONLY|O_LARGEFILE|O_NOFOLLOW) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0 ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbe83b714) = -1 ENOTTY
Quoted 1 line
Quoted 1 line
(Inappropriate ioctl for device)
read(3,
Message from syslogd at localhost at Mar 9 23:54:39 ...
kernel:[ 3097.357696] Internal error: Oops: 80000007 [#2] ARM
So that would be:
./devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1/events/in_intensity_both_thresh_rising_en

Quoted 8 lines

And indeed, manually cat-ing that file reproduces the problem.
pavel at n900:/sys/devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1$ cat name
tsl2563
I can not find tsl2563 in MAINTAINERS, file is ./drivers/iio/light/tsl2563.c . I added few people pointed by git log.

The driver registers event attributes, but does not provide a handle to access those attributes.

Now the question is how to best handle this case.

1) Return an error when the device is registered and abort registration
2) Skip registering the event attributes
3) Skip registering the event attributes, but print a warning
4) Register the attributes, but return an error when they are accessed

I'd prefer 2 since it offers a nice method of disabling all events for a device (e.g. if not interrupt is provided).

On the other hand it could cause some confusion during development, potentially causing the developer to wonder why he doesn't get any event attributes even though he setup his channel description to have event attributes.

Patch for 2.

drivers/iio/industrialio-event.c +2 -1

@@ -477,7 +477,8 @@ int iio_device_register_eventset(struct iio_dev
 	struct attribute **attr;
 
 	if (!(indio_dev->info->event_attrs ||
-	      iio_check_for_dynamic_events(indio_dev)))
+	      iio_check_for_dynamic_events(indio_dev)) ||
+	    !indio_dev->info->read_event_config)
 		return 0;
 
 	indio_dev->event_interface =

Pavel Machek

author Tested-by

2018-03-10 12:00 UTC #5 lore raw

Hi!

Quoted 33 lines · Lars-Peter Clausen

On 03/10/2018 12:01 AM, Pavel Machek wrote:
[...]
Quoted 17 lines
Quoted 1 line
What file are you opening to cause this?
Strace says:
openat(7, "in_intensity_both_thresh_rising_en",
Quoted 1 line
Quoted 1 line
O_RDONLY|O_LARGEFILE|O_NOFOLLOW) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0 ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbe83b714) = -1 ENOTTY
Quoted 1 line
Quoted 1 line
(Inappropriate ioctl for device)
read(3,
Message from syslogd at localhost at Mar 9 23:54:39 ...
kernel:[ 3097.357696] Internal error: Oops: 80000007 [#2] ARM
So that would be:
./devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1/events/in_intensity_both_thresh_rising_en
Quoted 8 lines
And indeed, manually cat-ing that file reproduces the problem.
pavel at n900:/sys/devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1$ cat name
tsl2563
I can not find tsl2563 in MAINTAINERS, file is ./drivers/iio/light/tsl2563.c . I added few people pointed by git log.
The driver registers event attributes, but does not provide a handle to access those attributes.
Now the question is how to best handle this case.

Quoted 7 lines

1) Return an error when the device is registered and abort registration
2) Skip registering the event attributes
3) Skip registering the event attributes, but print a warning
4) Register the attributes, but return an error when they are accessed
I'd prefer 2 since it offers a nice method of disabling all events for a device (e.g. if not interrupt is provided).

2 works for me.

Tested-by Pavel Machek <[email protected]>

Reported-by Pavel Machek <[email protected]>

Now grep -ri asdfasdf /sys finishes.

Thanks,
Pavel

Quoted 12 lines

drivers/iio/industrialio-event.c +2 -1

@@ -477,7 +477,8 @@ int iio_device_register_eventset(struct iio_dev
 	struct attribute **attr;
 
 	if (!(indio_dev->info->event_attrs ||
-	      iio_check_for_dynamic_events(indio_dev)))
+	      iio_check_for_dynamic_events(indio_dev)) ||
+	    !indio_dev->info->read_event_config)
 		return 0;
 
 	indio_dev->event_interface =

Signature · 9 lines

(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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Jonathan Cameron

maintainer

2018-03-10 17:59 UTC #6 lore raw

Quoted 44 lines · On Sat, 10 Mar 2018 13:00:53 +0100 Pavel Machek <[email protected]> wrote:

Hi!
Quoted 33 lines · Lars-Peter Clausen
On 03/10/2018 12:01 AM, Pavel Machek wrote:
[...]
Quoted 17 lines
Quoted 1 line
What file are you opening to cause this?
Strace says:
openat(7, "in_intensity_both_thresh_rising_en",
Quoted 1 line
Quoted 1 line
O_RDONLY|O_LARGEFILE|O_NOFOLLOW) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0 ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbe83b714) = -1 ENOTTY
Quoted 1 line
Quoted 1 line
(Inappropriate ioctl for device)
read(3,
Message from syslogd at localhost at Mar 9 23:54:39 ...
kernel:[ 3097.357696] Internal error: Oops: 80000007 [#2] ARM
So that would be:
./devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1/events/in_intensity_both_thresh_rising_en
Quoted 8 lines
And indeed, manually cat-ing that file reproduces the problem.
pavel at n900:/sys/devices/platform/68000000.ocp/48072000.i2c/i2c-2/2-0029/iio:device1$ cat name
tsl2563
I can not find tsl2563 in MAINTAINERS, file is ./drivers/iio/light/tsl2563.c . I added few people pointed by git log.
The driver registers event attributes, but does not provide a handle to access those attributes.
Now the question is how to best handle this case.
Quoted 7 lines
1) Return an error when the device is registered and abort registration
2) Skip registering the event attributes
3) Skip registering the event attributes, but print a warning
4) Register the attributes, but return an error when they are accessed
I'd prefer 2 since it offers a nice method of disabling all events for a device (e.g. if not interrupt is provided).

Quoted 6 lines

2 works for me.
Tested-by Pavel Machek <[email protected]>
Reported-by Pavel Machek <[email protected]>
Now grep -ri asdfasdf /sys finishes.

Hmm. I'd count this as a good general prevention of what is actually a driver bug. The driver should either have failed or as has been suggested should have come up without the event sysfs attributes by registering different abilities.

So I'm favour of this change, but from a semantic point of view I'd like the addition of a warning for this case and ideally for the driver to be fixed to not attempt to add them (two iio_info structures which is what a lot of other drivers do to allow them to work with and without the interrupt being available.).

Anyhow, Lars, please send a formal patch for the below and we'll get that headed for mainline asap.

Quoted 17 lines

Thanks,
Pavel

Quoted 12 lines

drivers/iio/industrialio-event.c +2 -1

@@ -477,7 +477,8 @@ int iio_device_register_eventset(struct iio_dev
 	struct attribute **attr;
 
 	if (!(indio_dev->info->event_attrs ||
-	      iio_check_for_dynamic_events(indio_dev)))
+	      iio_check_for_dynamic_events(indio_dev)) ||
+	    !indio_dev->info->read_event_config)
 		return 0;
 
 	indio_dev->event_interface =