Initial PWM support for the CHIP even though the base .dtb does not support, this is untested

source/c_pwm.c

@@ -0,0 +1,291 @@
+/*
+Copyright (c) 2016 Robert Wolterman
+
+Original BBIO Author Justin Cooper
+Modified for CHIP_IO Author Robert Wolterman
+
+This file incorporates work covered by the following copyright and
+permission notice, all modified code adopts the original license:
+
+Copyright (c) 2013 Adafruit
+Author: Justin Cooper
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include "c_pwm.h"
+#include "common.h"
+
+#define KEYLEN 7
+
+#define PERIOD 0
+#define DUTY 1
+
+int pwm_initialized = 0;
+
+// pwm exports
+struct pwm_exp
+{
+    char key[KEYLEN+1]; /* leave room for terminating NUL byte */
+    int period_fd;
+    int duty_fd;
+    int polarity_fd;
+    unsigned long duty;
+    unsigned long period_ns;
+    struct pwm_exp *next;
+};
+struct pwm_exp *exported_pwms = NULL;
+
+struct pwm_exp *lookup_exported_pwm(const char *key)
+{
+    struct pwm_exp *pwm = exported_pwms;
+
+    while (pwm != NULL)
+    {
+        if (strcmp(pwm->key, key) == 0) {
+            return pwm;
+        }
+        pwm = pwm->next;
+    }
+
+    return NULL; /* standard for pointers */
+}
+
+int initialize_pwm(void)
+{
+    if  (!pwm_initialized) {
+        int fd, len;
+        char str_gpio[2];
+        // Per https://github.com/NextThingCo/CHIP-linux/pull/4
+        // we need to export 0 here to enable pwm0
+        int gpio = 0;
+
+        if ((fd = open("/sys/class/pwm/pwmchip0/export", O_WRONLY)) < 0)
+        {
+            return -1;
+        }
+        len = snprintf(str_gpio, sizeof(str_gpio), "%d", gpio);
+        write(fd, str_gpio, len);
+        close(fd);
+
+        pwm_initialized = 1;
+        return 1;
+    }
+
+    return 0;
+}
+
+int pwm_set_frequency(const char *key, float freq) {
+    int len;
+    char buffer[20];
+    unsigned long period_ns;
+    struct pwm_exp *pwm;
+
+    if (freq <= 0.0)
+        return -1;
+
+    pwm = lookup_exported_pwm(key);
+
+    if (pwm == NULL) {
+        return -1;
+    }
+
+    period_ns = (unsigned long)(1e9 / freq);
+
+    if (period_ns != pwm->period_ns) {
+        pwm->period_ns = period_ns;
+
+        len = snprintf(buffer, sizeof(buffer), "%lu", period_ns);
+        write(pwm->period_fd, buffer, len);
+    }
+
+    return 1;
+}
+
+int pwm_set_polarity(const char *key, int polarity) {
+    int len;
+    char buffer[7]; /* allow room for trailing NUL byte */
+    struct pwm_exp *pwm;
+
+    pwm = lookup_exported_pwm(key);
+
+    if (pwm == NULL) {
+        return -1;
+    }
+
+    len = snprintf(buffer, sizeof(buffer), "%d", polarity);
+    write(pwm->polarity_fd, buffer, len);
+
+    return 0;
+}
+
+int pwm_set_duty_cycle(const char *key, float duty) {
+    int len;
+    char buffer[20];
+    struct pwm_exp *pwm;
+
+    if (duty < 0.0 || duty > 100.0)
+        return -1;
+
+    pwm = lookup_exported_pwm(key);
+
+    if (pwm == NULL) {
+        return -1;
+    }
+
+    pwm->duty = (unsigned long)(pwm->period_ns * (duty / 100.0));
+
+    len = snprintf(buffer, sizeof(buffer), "%lu", pwm->duty);
+    write(pwm->duty_fd, buffer, len);
+
+    return 0;
+}
+
+int pwm_start(const char *key, float duty, float freq, int polarity)
+{
+    char pwm_base_path[45];
+    char period_path[50];
+    char duty_path[50];
+    char polarity_path[55];
+    int period_fd, duty_fd, polarity_fd;
+    struct pwm_exp *new_pwm, *pwm;
+
+    if(!pwm_initialized) {
+        initialize_pwm();
+    }
+
+    //setup the pwm base path, the chip only has one pwm
+    snprintf(pwm_base_path, sizeof(pwm_base_path), "/sys/class/pwm/pwmchip0/%d", "pwm0");
+
+    //create the path for the period and duty
+    snprintf(period_path, sizeof(period_path), "%s/period", pwm_base_path);
+    snprintf(duty_path, sizeof(duty_path), "%s/duty", pwm_base_path);
+    snprintf(polarity_path, sizeof(polarity_path), "%s/polarity", pwm_base_path);
+
+    //add period and duty fd to pwm list
+    if ((period_fd = open(period_path, O_RDWR)) < 0)
+        return -1;
+
+
+    if ((duty_fd = open(duty_path, O_RDWR)) < 0) {
+        //error, close already opened period_fd.
+        close(period_fd);
+        return -1;
+    }
+
+    if ((polarity_fd = open(polarity_path, O_RDWR)) < 0) {
+        //error, close already opened period_fd and duty_fd.
+        close(period_fd);
+        close(duty_fd);
+        return -1;
+    }
+
+    // add to list
+    new_pwm = malloc(sizeof(struct pwm_exp));
+    if (new_pwm == 0) {
+        return -1; // out of memory
+    }
+
+    strncpy(new_pwm->key, key, KEYLEN);  /* can leave string unterminated */
+    new_pwm->key[KEYLEN] = '\0'; /* terminate string */
+    new_pwm->period_fd = period_fd;
+    new_pwm->duty_fd = duty_fd;
+    new_pwm->polarity_fd = polarity_fd;
+    new_pwm->next = NULL;
+
+    if (exported_pwms == NULL)
+    {
+        // create new list
+        exported_pwms = new_pwm;
+    } else {
+        // add to end of existing list
+        pwm = exported_pwms;
+        while (pwm->next != NULL)
+            pwm = pwm->next;
+        pwm->next = new_pwm;
+    }
+
+    pwm_set_frequency(key, freq);
+    pwm_set_polarity(key, polarity);
+    pwm_set_duty_cycle(key, duty);
+
+    return 1;
+}
+
+int pwm_disable(const char *key)
+{
+    struct pwm_exp *pwm, *temp, *prev_pwm = NULL;
+    char fragment[18];
+
+    int fd, len;
+    char str_gpio[2];
+    // Per https://github.com/NextThingCo/CHIP-linux/pull/4
+    // we need to export 0 here to enable pwm0
+    int gpio = 0;
+
+    if ((fd = open("/sys/class/pwm/pwmchip0/unexport", O_WRONLY)) < 0)
+    {
+        return -1;
+    }
+    len = snprintf(str_gpio, sizeof(str_gpio), "%d", gpio);
+    write(fd, str_gpio, len);
+    close(fd);
+
+    // remove from list
+    pwm = exported_pwms;
+    while (pwm != NULL)
+    {
+        if (strcmp(pwm->key, key) == 0)
+        {
+            //close the fd
+            close(pwm->period_fd);
+            close(pwm->duty_fd);
+            close(pwm->polarity_fd);
+
+            if (prev_pwm == NULL)
+            {
+                exported_pwms = pwm->next;
+                prev_pwm = pwm;
+            } else {
+                prev_pwm->next = pwm->next;
+            }
+
+            temp = pwm;
+            pwm = pwm->next;
+            free(temp);
+        } else {
+            prev_pwm = pwm;
+            pwm = pwm->next;
+        }
+    }
+    return 0;
+}
+
+void pwm_cleanup(void)
+{
+    while (exported_pwms != NULL) {
+        pwm_disable(exported_pwms->key);
+    }
+}