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Subject[PATCH 1/2] pwm: sysfs: Set class on pwm devices
Date
From: Lars Poeschel <poeschel@lemonage.de>

This adds a class to exported pwm devices.
Exporting a pwm through sysfs did not yield udev events. The
dev_uevent_filter function does filter-out devices without a bus or
class.
This was already addressed in commit
commit 7e5d1fd75c3d ("pwm: Set class for exported channels in sysfs")
but this did cause problems and the commit got reverted with
commit c289d6625237 ("Revert "pwm: Set class for exported channels in
sysfs"")
Problem with the previous approach was, that there is a clash if we have
multiple pwmchips:
echo 0 > pwmchip0/export
echo 0 > pwmchip1/export
would both export /sys/class/pwm/pwm0 .

Now this patch changes the sysfs interface. We do include the pwmchip
number into the pwm directory that gets exported.
With the example above we get:
/sys/class/pwm/pwm-0-0
/sys/class/pwm/pwm-1-0
We maintain ABI backward compatibility through symlinks.
/sys/class/pwm/pwmchip0/pwm0
/sys/class/pwm/pwmchip1/pwm0
are now symbolic links to the new names.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
---
drivers/pwm/sysfs.c | 57 +++++++++++++++++++++++++++++++++++++--------
1 file changed, 47 insertions(+), 10 deletions(-)

diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c
index 449dbc0f49ed..c708da17a857 100644
--- a/drivers/pwm/sysfs.c
+++ b/drivers/pwm/sysfs.c
@@ -240,8 +240,10 @@ static void pwm_export_release(struct device *child)

static int pwm_export_child(struct device *parent, struct pwm_device *pwm)
{
+ struct pwm_chip *chip = dev_get_drvdata(parent);
struct pwm_export *export;
char *pwm_prop[2];
+ char *link_name;
int ret;

if (test_and_set_bit(PWMF_EXPORTED, &pwm->flags))
@@ -256,25 +258,39 @@ static int pwm_export_child(struct device *parent, struct pwm_device *pwm)
export->pwm = pwm;
mutex_init(&export->lock);

+ export->child.class = parent->class;
export->child.release = pwm_export_release;
export->child.parent = parent;
export->child.devt = MKDEV(0, 0);
export->child.groups = pwm_groups;
- dev_set_name(&export->child, "pwm%u", pwm->hwpwm);
+ dev_set_name(&export->child, "pwm-%u-%u", chip->base, pwm->hwpwm);

ret = device_register(&export->child);
- if (ret) {
- clear_bit(PWMF_EXPORTED, &pwm->flags);
- put_device(&export->child);
- export = NULL;
- return ret;
+ if (ret)
+ goto error;
+
+ link_name = kasprintf(GFP_KERNEL, "pwm%u", pwm->hwpwm);
+ if (link_name == NULL) {
+ ret = -ENOMEM;
+ goto dev_unregister;
}
- pwm_prop[0] = kasprintf(GFP_KERNEL, "EXPORT=pwm%u", pwm->hwpwm);
+
+ pwm_prop[0] = kasprintf(GFP_KERNEL, "EXPORT=%s",
+ export->child.kobj.name);
pwm_prop[1] = NULL;
kobject_uevent_env(&parent->kobj, KOBJ_CHANGE, pwm_prop);
kfree(pwm_prop[0]);

- return 0;
+ ret = sysfs_create_link(&parent->kobj, &export->child.kobj, link_name);
+ return ret;
+
+dev_unregister:
+ device_unregister(&export->child);
+error:
+ clear_bit(PWMF_EXPORTED, &pwm->flags);
+ put_device(&export->child);
+ export = NULL;
+ return ret;
}

static int pwm_unexport_match(struct device *child, void *data)
@@ -286,6 +302,7 @@ static int pwm_unexport_child(struct device *parent, struct pwm_device *pwm)
{
struct device *child;
char *pwm_prop[2];
+ char *link_name;

if (!test_and_clear_bit(PWMF_EXPORTED, &pwm->flags))
return -ENODEV;
@@ -294,7 +311,11 @@ static int pwm_unexport_child(struct device *parent, struct pwm_device *pwm)
if (!child)
return -ENODEV;

- pwm_prop[0] = kasprintf(GFP_KERNEL, "UNEXPORT=pwm%u", pwm->hwpwm);
+ link_name = kasprintf(GFP_KERNEL, "pwm%u", pwm->hwpwm);
+ if (link_name)
+ sysfs_delete_link(&parent->kobj, &child->kobj, link_name);
+
+ pwm_prop[0] = kasprintf(GFP_KERNEL, "UNEXPORT=%s", child->kobj.name);
pwm_prop[1] = NULL;
kobject_uevent_env(&parent->kobj, KOBJ_CHANGE, pwm_prop);
kfree(pwm_prop[0]);
@@ -365,13 +386,29 @@ static ssize_t npwm_show(struct device *parent, struct device_attribute *attr,
}
static DEVICE_ATTR_RO(npwm);

+static umode_t pwm_is_visible(struct kobject *kobj, struct attribute *attr,
+ int n)
+{
+ struct device *dev = container_of(kobj, struct device, kobj);
+
+ if (dev->groups == pwm_groups)
+ return 0;
+
+ return attr->mode;
+}
+
static struct attribute *pwm_chip_attrs[] = {
&dev_attr_export.attr,
&dev_attr_unexport.attr,
&dev_attr_npwm.attr,
NULL,
};
-ATTRIBUTE_GROUPS(pwm_chip);
+
+static const struct attribute_group pwm_chip_group = {
+ .attrs = pwm_chip_attrs,
+ .is_visible = pwm_is_visible,
+};
+__ATTRIBUTE_GROUPS(pwm_chip);

/* takes export->lock on success */
static struct pwm_export *pwm_class_get_state(struct device *parent,
--
2.28.0
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