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68 lines
2.3 KiB
Diff
68 lines
2.3 KiB
Diff
From 7f838c5c5229eb7531112fe0aa5539076878fb88 Mon Sep 17 00:00:00 2001
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From: Fabrice Gasnier <fabrice.gasnier@st.com>
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Date: Mon, 1 Oct 2018 15:23:56 +0200
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Subject: [PATCH 310/432] Revert "pwm: Set class for exported channels in
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sysfs"
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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commit c289d6625237aa785b484b4e94c23b3b91ea7e60 upstream.
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This reverts commit 7e5d1fd75c3dde9fc10c4472b9368089d1b81d00 ("pwm: Set
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class for exported channels in sysfs") as it causes regression with
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multiple pwm chip[1], when exporting a pwm channel (echo X > export):
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- ABI (Documentation/ABI/testing/sysfs-class-pwm) states pwmX should be
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created in /sys/class/pwm/pwmchipN/pwmX
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- Reverted patch causes new entry to be also created directly in
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/sys/class/pwm/pwmX
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- 1st time, exporting pwmX will create an entry in /sys/class/pwm/pwmX
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- class attributes are added under pwmX folder, such as export, unexport
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npwm, symlinks. This is wrong as it belongs to pwmchipN. It may cause
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bad behavior and report wrong values.
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- when another export happens on another pwmchip, it can't be created
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(e.g. -EEXIST). This is causing the issue with multiple pwmchip.
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Example on stm32 (stm32429i-eval) platform:
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$ ls /sys/class/pwm
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pwmchip0 pwmchip4
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$ cd /sys/class/pwm/pwmchip0/
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$ echo 0 > export
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$ ls /sys/class/pwm
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pwm0 pwmchip0 pwmchip4
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$ cd /sys/class/pwm/pwmchip4/
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$ echo 0 > export
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sysfs: cannot create duplicate filename '/class/pwm/pwm0'
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...Exception stack follows...
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This is also seen on other platform [2]
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[1] https://lkml.org/lkml/2018/9/25/713
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[2] https://lkml.org/lkml/2018/9/25/447
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Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
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Tested-by: Gottfried Haider <gottfried.haider@gmail.com>
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Tested-by: Michal Vokáč <michal.vokac@ysoft.com>
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Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
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---
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drivers/pwm/sysfs.c | 1 -
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1 file changed, 1 deletion(-)
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diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c
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index 7c71cdb8a9d8..4726d43aaa0c 100644
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--- a/drivers/pwm/sysfs.c
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+++ b/drivers/pwm/sysfs.c
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@@ -263,7 +263,6 @@ static int pwm_export_child(struct device *parent, struct pwm_device *pwm)
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export->pwm = pwm;
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mutex_init(&export->lock);
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- export->child.class = parent->class;
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export->child.release = pwm_export_release;
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export->child.parent = parent;
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export->child.devt = MKDEV(0, 0);
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--
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2.19.1
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