diff options
| author | Uwe Kleine-König <u.kleine-koenig@baylibre.com> | 2025-04-30 13:56:01 +0200 |
|---|---|---|
| committer | Uwe Kleine-König <ukleinek@kernel.org> | 2025-07-07 08:39:33 +0200 |
| commit | 9c06f26ba5f5da14bcac405c7a652dcf578a785d (patch) | |
| tree | 1b9f4076877d18868942d3991146769b198d9324 /include/linux | |
| parent | 505b730ede7f5c4083ff212aa955155b5b92e574 (diff) | |
pwm: Add support for pwmchip devices for faster and easier userspace access
With this change each pwmchip defining the new-style waveform callbacks
can be accessed from userspace via a character device. Compared to the
sysfs-API this is faster and allows to pass the whole configuration in a
single ioctl allowing atomic application and thus reducing glitches.
On an STM32MP13 I see:
root@DistroKit:~ time pwmtestperf
real 0m 1.27s
user 0m 0.02s
sys 0m 1.21s
root@DistroKit:~ rm /dev/pwmchip0
root@DistroKit:~ time pwmtestperf
real 0m 3.61s
user 0m 0.27s
sys 0m 3.26s
pwmtestperf does essentially:
for i in 0 .. 50000:
pwm_set_waveform(duty_length_ns=i, period_length_ns=50000, duty_offset_ns=0)
and in the presence of /dev/pwmchip0 is uses the ioctls introduced here,
without that device it uses /sys/class/pwm/pwmchip0.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/ad4a4e49ae3f8ea81e23cac1ac12b338c3bf5c5b.1746010245.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/pwm.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 63a17d2b4ec8..2492c91452f9 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -2,6 +2,7 @@ #ifndef __LINUX_PWM_H #define __LINUX_PWM_H +#include <linux/cdev.h> #include <linux/device.h> #include <linux/err.h> #include <linux/module.h> @@ -311,6 +312,7 @@ struct pwm_ops { /** * struct pwm_chip - abstract a PWM controller * @dev: device providing the PWMs + * @cdev: &struct cdev for this device * @ops: callbacks for this PWM controller * @owner: module providing this chip * @id: unique number of this PWM chip @@ -325,6 +327,7 @@ struct pwm_ops { */ struct pwm_chip { struct device dev; + struct cdev cdev; const struct pwm_ops *ops; struct module *owner; unsigned int id; |