File Permissions for exported GPIO pins changed in Kernel 4.1.6

[herbertkoenig]

Hi,

before my latest update, when exporting a GPIO pin like:
echo 17 > /sys/class/gpio/export
the file /sys/class/gpio/gpio17/direction
would be read/writeable by owner root and group gpio. Same holds for the value file and the gpio17 folder.

In the 4.1.6 kernel this has changed as follows:
The gpio17 folder can be read an written by everyone.
The file /sys/class/gpio/gpio17/direction is now owned by root and in group root (not gpio) and is readable by everyone and changeable only by the owner. Same for the value file.

old kernel:
Linux herpi1 3.18.11+ #781 PREEMPT Tue Apr 21 18:02:18 BST 2015 armv6l GNU/Linux
new kernel:
Linux herpi4 4.1.6+ #810 PREEMPT Tue Aug 18 15:19:58 BST 2015 armv6l GNU/Linux

[popcornmix]

Looks like something may have changed in the later kernel where
/sys/devices/soc/*.gpio/gpio is now /sys/devices/platform/soc/*.gpio/gpio

Can you try editing:
/lib/udev/rules.d/60-python-pifacecommon.rules and
/lib/udev/rules.d/60-python3-pifacecommon.rules (if they both exist) to be:

KERNEL=="spidev*", GROUP="spi", MODE="0660"
SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'chown -R root:gpio /sys/class/gpio && chmod -R 770 /sys/class/gpio; chown -R root:gpio /sys/devices/virtual/gpio && chmod -R 770 /sys/devices/virtual/gpio; chown -R root:gpio /sys/devices/platform/soc/*.gpio/gpio && chmod -R 770 /sys/devices/platform/soc/*.gpio/gpio'"

Reboot and report back if that fixes it.

[herbertkoenig]

Hi,

seems to work, I'll report back with more detail soon.

Thanks,

Herbert

Am 24.08.2015 um 16:33 schrieb popcornmix:

Looks like something may have changed in the later kernel where
|/sys/devices/soc/.gpio/gpio| is now
|/sys/devices/platform/soc/.gpio/gpio|

Can you try editing:
|/lib/udev/rules.d/60-python-pifacecommon.rules| and
|/lib/udev/rules.d/60-python3-pifacecommon.rules| (if they both exist)
to be:

|KERNEL=="spidev_", GROUP="spi", MODE="0660" SUBSYSTEM=="gpio_",
PROGRAM="/bin/sh -c 'chown -R root:gpio /sys/class/gpio && chmod -R
770 /sys/class/gpio; chown -R root:gpio /sys/devices/virtual/gpio &&
chmod -R 770 /sys/devices/virtual/gpio; chown -R root:gpio
/sys/devices/platform/soc/.gpio/gpio && chmod -R 770
/sys/devices/platform/soc/.gpio/gpio'" |

Reboot and report back if that fixes it.

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#1117 (comment).

[herbertkoenig]

Hi,

I can confirm the fix solves my problem.

The differences in the file permissions of the folder
/sys/class/gpio/gpio17
I thought I still spotted were due to me misinterpreting the slightly
changed file permissions dialog in the new kernel.

Thanks for the fix, I'll report it in the Raspi Forum where I initially
raised the topic.

https://www.raspberrypi.org/forums/viewtopic.php?f=66&t=118879

Cheers,

Herbert

Am 24.08.2015 um 16:33 schrieb popcornmix:

Looks like something may have changed in the later kernel where
|/sys/devices/soc/.gpio/gpio| is now
|/sys/devices/platform/soc/.gpio/gpio|

Can you try editing:
|/lib/udev/rules.d/60-python-pifacecommon.rules| and
|/lib/udev/rules.d/60-python3-pifacecommon.rules| (if they both exist)
to be:

|KERNEL=="spidev_", GROUP="spi", MODE="0660" SUBSYSTEM=="gpio_",
PROGRAM="/bin/sh -c 'chown -R root:gpio /sys/class/gpio && chmod -R
770 /sys/class/gpio; chown -R root:gpio /sys/devices/virtual/gpio &&
chmod -R 770 /sys/devices/virtual/gpio; chown -R root:gpio
/sys/devices/platform/soc/.gpio/gpio && chmod -R 770
/sys/devices/platform/soc/.gpio/gpio'" |

Reboot and report back if that fixes it.

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#1117 (comment).

[mauritslamers]

I found that after upgrading to Raspian jessie the udev rules files mentioned above did not exist. Creating the first one and then doing a restart solved the issue.

[popcornmix]

@mauritslamers
How did you upgrade? Clean install or by changing apt sources and dist upgrade?
On a clean jessie image the permissions seem okay to me.

[christophfroehlich]

I updated via apt-get upgrade to 4.1.7+ and had the same problem. fixing 60-python-pifacecommon.rules did work for me.

[mauritslamers]

@popcornmix I upgraded by changing apt sources and then running an apt-get dist-upgrade.

[popcornmix]

I think you'll probably have to manually edit if you manually upgraded, but @XECDesign can confirm if an upgrade path is planned.
A clean install of jessie should have the correct udev rules.

[mauritslamers]

@popcornmix In order to edit, the file should exist in the first place. In my case it didn't, but creating it, adding the content as mentioned above fixed the problem of not being able to use the GPIO as the pi user.

[XECDesign]

I'm not sure that an upgrade path is planned for this particular issue. It would still require the user to install a package which would handle such things. However, we can create a raspberrypi-sys-mods package for future releases.

[rpakdel]

FYI, I did a clean install of Raspbian Jessie from https://www.raspberrypi.org/downloads/raspbian/ last week.

The permissions don't work (Node.js gpio access gives permission error when not run as root). The udev rules files also don't exist. I've added the files manually (copied from my working Wheezy install) and rebooted but they're still not working (I gave up quickly).

[XECDesign]

People looking at /lib/udev/rules.d/ and assuming the files are missing are looking in the wrong place.

The rules are in /etc/udev/rules.d/99-com.rules

I don't know anything about node.js or what exact method you're using to access GPIO. Perhaps it's a /dev/mem mmap method which will always need root?

[rpakdel]

Thanks for pointing me to the right direction. The 99-com.rules file is missing setting the group permissions on /sys/devices/soc. Appending the line below to PROGRAM fixes this

chown -R root:gpio /sys/devices/soc/*.gpio/gpio && chmod -R 770 /sys/devices/soc/*.gpio/gpio

Test:

pi@raspberrypi /sys/class/gpio $ ls -la
total 0
drwxrwx--- 2 root gpio 0 Oct 14 04:56 .
drwxr-xr-x 38 root root 0 Oct 14 04:46 ..
-rwxrwx--- 1 root gpio 4096 Oct 14 04:51 export
lrwxrwxrwx 1 root gpio 0 Oct 11 09:17 gpiochip0 -> ../../devices/soc/20200000.gpio/gpio/gpiochip0
-rwxrwx--- 1 root gpio 4096 Oct 14 04:56 unexport

pi@raspberrypi /sys/class/gpio $ echo 17 > export
pi@raspberrypi /sys/class/gpio $ ls -la gpio17/
total 0
drwxrwx--- 3 root gpio 0 Oct 14 04:56 .
drwxrwx--- 4 root gpio 0 Oct 14 04:56 ..
-rwxrwx--- 1 root gpio 4096 Oct 14 04:56 active_low
lrwxrwxrwx 1 root gpio 0 Oct 14 04:56 device -> ../../../20200000.gpio
-rwxrwx--- 1 root gpio 4096 Oct 14 04:56 direction
-rwxrwx--- 1 root gpio 4096 Oct 14 04:56 edge
drwxrwx--- 2 root gpio 0 Oct 14 04:56 power
lrwxrwxrwx 1 root gpio 0 Oct 14 04:56 subsystem -> ../../../../../class/gpio
-rwxrwx--- 1 root gpio 4096 Oct 14 04:56 uevent
-rwxrwx--- 1 root gpio 4096 Oct 14 04:56 value

[XECDesign]

@rpakdel What does uname -a say?