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/**
 * @file PWM servo driver.
 *
 * The pwm_servo driver supports servos connected to STM32 timer
 * blocks.
 *
 * Servo values can be set either with the PWM_SERVO_SET ioctl, or
 * by writing an array of servo_position_t values to the device.
 * Writing a value of 0 to a channel suppresses any output for that
 * channel.
 *
 * Servo values can be read back either with the PWM_SERVO_GET
 * ioctl, or by reading an array of servo_position_t values
 * from the device.
 *
 * Attempts to set a channel that is not configured are ignored,
 * and unconfigured channels always read zero.
 *
 * The PWM_SERVO_ARM / PWM_SERVO_DISARM calls globally arm
 * (enable) and disarm (disable) all servo outputs.
 */

#include <sys/ioctl.h>

#define _PWM_SERVO_BASE		0x7500
#define PWM_SERVO_ARM		_IOC(_PWM_SERVO_BASE, 0)
#define PWM_SERVO_DISARM	_IOC(_PWM_SERVO_BASE, 1)

#define PWM_SERVO_SET(_servo)	_IOC(_PWM_SERVO_BASE, 0x20 + _servo)
#define PWM_SERVO_GET(_servo)	_IOC(_PWM_SERVO_BASE, 0x40 + _servo)

typedef uint16_t	servo_position_t;

/* configuration limits */
#define PWM_SERVO_MAX_TIMERS	3
#define PWM_SERVO_MAX_CHANNELS	8

struct pwm_servo_config {
	/* rate (in Hz) of PWM updates */
	uint32_t	update_rate;

	/* array of timers dedicated to PWM servo use */
	struct pwm_servo_timer {
		uint32_t	base;
		uint32_t	clock_register;
		uint32_t	clock_bit;
		uint32_t	clock_freq;
	} timers[PWM_SERVO_MAX_TIMERS];

	/* array of channels in logical order */
	struct pwm_servo_channel {
		uint32_t	gpio;
		uint8_t		timer_index;
		uint8_t		timer_channel;
		servo_position_t default_value;
	} channels[PWM_SERVO_MAX_CHANNELS];
};

extern int	pwm_servo_init(const struct pwm_servo_config *config);