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c289d66252
This reverts commit 7e5d1fd75c ("pwm: Set
class for exported channels in sysfs") as it causes regression with
multiple pwm chip[1], when exporting a pwm channel (echo X > export):
- ABI (Documentation/ABI/testing/sysfs-class-pwm) states pwmX should be
created in /sys/class/pwm/pwmchipN/pwmX
- Reverted patch causes new entry to be also created directly in
/sys/class/pwm/pwmX
- 1st time, exporting pwmX will create an entry in /sys/class/pwm/pwmX
- class attributes are added under pwmX folder, such as export, unexport
npwm, symlinks. This is wrong as it belongs to pwmchipN. It may cause
bad behavior and report wrong values.
- when another export happens on another pwmchip, it can't be created
(e.g. -EEXIST). This is causing the issue with multiple pwmchip.
Example on stm32 (stm32429i-eval) platform:
$ ls /sys/class/pwm
pwmchip0 pwmchip4
$ cd /sys/class/pwm/pwmchip0/
$ echo 0 > export
$ ls /sys/class/pwm
pwm0 pwmchip0 pwmchip4
$ cd /sys/class/pwm/pwmchip4/
$ echo 0 > export
sysfs: cannot create duplicate filename '/class/pwm/pwm0'
...Exception stack follows...
This is also seen on other platform [2]
[1] https://lkml.org/lkml/2018/9/25/713
[2] https://lkml.org/lkml/2018/9/25/447
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Tested-by: Gottfried Haider <gottfried.haider@gmail.com>
Tested-by: Michal Vokáč <michal.vokac@ysoft.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.