git.openwrt.org Git - openwrt/staging/aparcar.git/blob

   1 From d499c8f6171122d78a90c3a6403ac7c0c1f50887 Mon Sep 17 00:00:00 2001
   2 From: Fabrice Gasnier <fabrice.gasnier@st.com>
   3 Date: Mon, 1 Oct 2018 15:23:56 +0200
   4 Subject: [PATCH 310/703] Revert "pwm: Set class for exported channels in
   5  sysfs"
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   9
  10 commit c289d6625237aa785b484b4e94c23b3b91ea7e60 upstream.
  11
  12 This reverts commit 7e5d1fd75c3dde9fc10c4472b9368089d1b81d00 ("pwm: Set
  13 class for exported channels in sysfs") as it causes regression with
  14 multiple pwm chip[1], when exporting a pwm channel (echo X > export):
  15
  16 - ABI (Documentation/ABI/testing/sysfs-class-pwm) states pwmX should be
  17   created in /sys/class/pwm/pwmchipN/pwmX
  18 - Reverted patch causes new entry to be also created directly in
  19   /sys/class/pwm/pwmX
  20 - 1st time, exporting pwmX will create an entry in /sys/class/pwm/pwmX
  21 - class attributes are added under pwmX folder, such as export, unexport
  22   npwm, symlinks. This is wrong as it belongs to pwmchipN. It may cause
  23   bad behavior and report wrong values.
  24 - when another export happens on another pwmchip, it can't be created
  25   (e.g. -EEXIST). This is causing the issue with multiple pwmchip.
  26
  27 Example on stm32 (stm32429i-eval) platform:
  28 $ ls /sys/class/pwm
  29 pwmchip0 pwmchip4
  30
  31 $ cd /sys/class/pwm/pwmchip0/
  32 $ echo 0 > export
  33 $ ls /sys/class/pwm
  34 pwm0 pwmchip0 pwmchip4
  35
  36 $ cd /sys/class/pwm/pwmchip4/
  37 $ echo 0 > export
  38 sysfs: cannot create duplicate filename '/class/pwm/pwm0'
  39 ...Exception stack follows...
  40
  41 This is also seen on other platform [2]
  42
  43 [1] https://lkml.org/lkml/2018/9/25/713
  44 [2] https://lkml.org/lkml/2018/9/25/447
  45
  46 Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
  47 Tested-by: Gottfried Haider <gottfried.haider@gmail.com>
  48 Tested-by: Michal Vokáč <michal.vokac@ysoft.com>
  49 Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
  50 ---
  51  drivers/pwm/sysfs.c | 1 -
  52  1 file changed, 1 deletion(-)
  53
  54 --- a/drivers/pwm/sysfs.c
  55 +++ b/drivers/pwm/sysfs.c
  56 @@ -263,7 +263,6 @@ static int pwm_export_child(struct devic
  57         export->pwm = pwm;
  58         mutex_init(&export->lock);
  59
  60 -       export->child.class = parent->class;
  61         export->child.release = pwm_export_release;
  62         export->child.parent = parent;
  63         export->child.devt = MKDEV(0, 0);