drv/pwm: move internals to separate header file

This makes the intent clearer and discourages improper use of the API.

Author: dlech

lib/pbio/drv/core.c

@@ -5,9 +5,9 @@
 
 #include <pbdrv/battery.h>
 #include <pbdrv/led.h>
-#include <pbdrv/pwm.h>
 
 #include "counter/counter.h"
+#include "pwm/pwm.h"
 
 /** Initializes all enabled drivers. */
 void pbdrv_init() {

lib/pbio/drv/pwm/pwm.h

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2020 The Pybricks Authors
+
+// Pulse width modulation (PWM) drivers
+
+#ifndef _PBDRV_PWM_PWM_H_
+#define _PBDRV_PWM_PWM_H_
+
+#include <stdint.h>
+
+#include <pbdrv/config.h>
+#include <pbdrv/pwm.h>
+#include <pbio/error.h>
+
+/**
+ * Driver callback functions.
+ */
+typedef struct {
+    /** Driver implementation of pbdrv_pwm_set_duty() */
+    pbio_error_t (*set_duty)(pbdrv_pwm_dev_t *dev, uint32_t ch, uint32_t value);
+} pbdrv_pwm_driver_funcs_t;
+
+struct _pbdrv_pwm_dev_t {
+    /** Platform data. */
+    const void *pdata;
+    /** Driver callback functions. */
+    const pbdrv_pwm_driver_funcs_t *funcs;
+    /** Private driver data */
+    void *priv;
+};
+
+#if PBDRV_CONFIG_PWM
+
+void pbdrv_pwm_init();
+
+#else // PBDRV_CONFIG_PWM
+
+#define pbdrv_pwm_init()
+
+#endif // PBDRV_CONFIG_PWM
+
+#endif // _PBDRV_PWM_PWM_H_

lib/pbio/drv/pwm/pwm_core.c

@@ -11,15 +11,14 @@
 #include <pbdrv/pwm.h>
 #include <pbio/error.h>
 
-#include "./pwm_stm32_tim.h"
-#include "./pwm_test.h"
-#include "./pwm_tlc5955_stm32.h"
+#include "pwm_stm32_tim.h"
+#include "pwm_test.h"
+#include "pwm_tlc5955_stm32.h"
+#include "pwm.h"
 
 
 static pbdrv_pwm_dev_t pbdrv_pwm_dev[PBDRV_CONFIG_PWM_NUM_DEV];
 
-/** @cond INTERNAL */
-
 /**
  * Initializes all PWM drivers.
  */
@@ -29,8 +28,6 @@ void pbdrv_pwm_init() {
     pbdrv_pwm_tlc5955_stm32_init(pbdrv_pwm_dev);
 }
 
-/** @endcond */
-
 /**
  * Gets the PWM device with the given ID.
  * @param [in]  id      The ID of the PWM device.

lib/pbio/drv/pwm/pwm_stm32_tim.c

@@ -14,7 +14,8 @@
 #include <pbdrv/pwm.h>
 #include <pbio/error.h>
 
-#include "./pwm_stm32_tim.h"
+#include "pwm_stm32_tim.h"
+#include "pwm.h"
 
 static pbio_error_t pbdrv_pwm_stm32_tim_set_duty(pbdrv_pwm_dev_t *dev, uint32_t ch, uint32_t value) {
     const pbdrv_pwm_stm32_tim_platform_data_t *pdata = dev->pdata;

lib/pbio/drv/pwm/pwm_tlc5955_stm32.c

@@ -20,7 +20,8 @@
 #include <pbio/error.h>
 #include <pbio/util.h>
 
-#include "./pwm_tlc5955_stm32.h"
+#include "pwm_tlc5955_stm32.h"
+#include "pwm.h"
 
 // size in bytes to hold 769-bit shift register data
 #define TLC5955_DATA_SIZE ((769 + 7) / 8)

lib/pbio/include/pbdrv/pwm.h

@@ -20,26 +20,8 @@
  */
 typedef struct _pbdrv_pwm_dev_t pbdrv_pwm_dev_t;
 
-/**
- * Driver callback functions.
- */
-typedef struct {
-    /** Driver implementation of pbdrv_pwm_set_duty() */
-    pbio_error_t (*set_duty)(pbdrv_pwm_dev_t *dev, uint32_t ch, uint32_t value);
-} pbdrv_pwm_driver_funcs_t;
-
-struct _pbdrv_pwm_dev_t {
-    /** Platform data. */
-    const void *pdata;
-    /** Driver callback functions. */
-    const pbdrv_pwm_driver_funcs_t *funcs;
-    /** Private driver data */
-    void *priv;
-};
-
 #if PBDRV_CONFIG_PWM
 
-void pbdrv_pwm_init();
 pbio_error_t pbdrv_pwm_get_dev(uint8_t id, pbdrv_pwm_dev_t **dev);
 pbio_error_t pbdrv_pwm_set_duty(pbdrv_pwm_dev_t *dev, uint32_t ch, uint32_t value);
 

lib/pbio/test/pwm.c

@@ -3,11 +3,13 @@
 
 #include <stdio.h>
 
+#include <tinytest.h>
+#include <tinytest_macros.h>
+
 #include <pbdrv/pwm.h>
 #include <pbio/error.h>
 
-#include <tinytest.h>
-#include <tinytest_macros.h>
+#include "../drv/pwm/pwm.h"
 
 typedef struct {
     uint32_t duty_channel;