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UPSTREAM: pwm: sysfs: Add PWM capture support

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Allow a user to read PWM capture results from sysfs. To start a capture
and read the result, simply read the file:

  $ cat $PWMCHIP/capture

The output format is "<period> <duty cycle>".

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
(cherry picked from commit 1a366fe9153f445e950a7a344932b7419aa83094)

Change-Id: I86326709c373630a9189232a1cf2804a1a6ed380
Signed-off-by: David Wu <david.wu@rock-chips.com>
This commit is contained in:
Lee Jones
2016-06-08 10:21:25 +01:00
committed by Huang, Tao
parent 76e1d28062
commit ea5d08da89
2 changed files with 26 additions and 0 deletions
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9
Documentation/ABI/testing/sysfs-class-pwm
View File

@@ -77,3 +77,12 @@ Description:
Enable/disable the PWM signal.
0 is disabled
1 is enabled
What: /sys/class/pwm/pwmchipN/pwmX/capture
Date: June 2016
KernelVersion: 4.8
Contact: Lee Jones <lee.jones@linaro.org>
Description:
Capture information about a PWM signal. The output format is a
pair unsigned integers (period and duty cycle), separated by a
single space.

17
drivers/pwm/sysfs.c
View File

@@ -208,16 +208,33 @@ static ssize_t polarity_store(struct device *child,
return ret ? : size;
}
static ssize_t capture_show(struct device *child,
struct device_attribute *attr,
char *buf)
{
struct pwm_device *pwm = child_to_pwm_device(child);
struct pwm_capture result;
int ret;
ret = pwm_capture(pwm, &result, jiffies_to_msecs(HZ));
if (ret)
return ret;
return sprintf(buf, "%u %u\n", result.period, result.duty_cycle);
}
static DEVICE_ATTR_RW(period);
static DEVICE_ATTR_RW(duty_cycle);
static DEVICE_ATTR_RW(enable);
static DEVICE_ATTR_RW(polarity);
static DEVICE_ATTR_RO(capture);
static struct attribute *pwm_attrs[] = {
&dev_attr_period.attr,
&dev_attr_duty_cycle.attr,
&dev_attr_enable.attr,
&dev_attr_polarity.attr,
&dev_attr_capture.attr,
NULL
};
ATTRIBUTE_GROUPS(pwm);