Re: [PATCH v4 4/7] pwm: Add support for pwmchip devices for faster and easier userspace access

[Kent Gibson <warthog618@gmail.com>]

On Fri, Sep 06, 2024 at 05:43:00PM +0200, Uwe Kleine-König wrote:
> 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 (on a stm32mp157 applying a new configuration
> takes approx 25% only) and allows to pass the whole configuration in a
> single ioctl allowing atomic application.
>
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
> ---

> +++ b/include/uapi/linux/pwm.h
> @@ -0,0 +1,24 @@
> +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
> +
> +#ifndef _UAPI_PWM_H_
> +#define _UAPI_PWM_H_
> +
> +#include <linux/ioctl.h>
> +#include <linux/types.h>
> +
> +struct pwmchip_waveform {
> +	__u32 hwpwm;
> +	__u32 __pad; /* padding, must be zero */
> +	__u64 period_length_ns;
> +	__u64 duty_length_ns;
> +	__u64 duty_offset_ns;
> +};
> +

Some documentation?

> +#define PWM_IOCTL_REQUEST	_IOW(0x75, 1, unsigned int)
> +#define PWM_IOCTL_FREE		_IOW(0x75, 2, unsigned int)
> +#define PWM_IOCTL_ROUNDWF	_IOWR(0x75, 3, struct pwmchip_waveform)
> +#define PWM_IOCTL_GETWF		_IOWR(0x75, 4, struct pwmchip_waveform)
> +#define PWM_IOCTL_SETROUNDEDWF	_IOW(0x75, 5, struct pwmchip_waveform)
> +#define PWM_IOCTL_SETEXACTWF	_IOW(0x75, 6, struct pwmchip_waveform)
> +
> +#endif /* _UAPI_PWM_H_ */
> --
> 2.45.2
>