vibrator: add support to use led-trigger interface

The existing vibrator HAL uses the timed_output interface which will
never be moved out of kernel's staging tree. The kernel already has a
similar feature with GPIO controlled LEDs and LED triggers. While a
vibrator is not an LED, the control model is the same and can be reused.
Additionally, DT bindings already exist for GPIO controlled LEDs.

This adds support for the LED device in addition to the timed_output
device. It uses the "transient" trigger for the LED device named
"vibrator".

Change-Id: I90d52d6e50d83d255f484db148064069504f78e0
Signed-off-by: Rob Herring <robh@kernel.org>

modules/vibrator/vibrator.c

@@ -21,11 +21,15 @@
 
 #include <malloc.h>
 #include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <math.h>
 
+#define TIMEOUT_STR_LEN         20
+
 static const char THE_DEVICE[] = "/sys/class/timed_output/vibrator/enable";
 
 static int vibra_exists() {
@@ -33,7 +37,6 @@ static int vibra_exists() {
 
     fd = TEMP_FAILURE_RETRY(open(THE_DEVICE, O_RDWR));
     if(fd < 0) {
-        ALOGE("Vibrator file does not exist : %d", fd);
         return 0;
     }
 
@@ -41,27 +44,24 @@ static int vibra_exists() {
     return 1;
 }
 
-static int sendit(unsigned int timeout_ms)
+static int write_value(const char *file, const char *value)
 {
     int to_write, written, ret, fd;
 
-    char value[20]; /* large enough for millions of years */
-
-    fd = TEMP_FAILURE_RETRY(open(THE_DEVICE, O_RDWR));
-    if(fd < 0) {
+    fd = TEMP_FAILURE_RETRY(open(file, O_WRONLY));
+    if (fd < 0) {
         return -errno;
     }
 
-    to_write = snprintf(value, sizeof(value), "%u\n", timeout_ms);
+    to_write = strlen(value) + 1;
     written = TEMP_FAILURE_RETRY(write(fd, value, to_write));
-
     if (written == -1) {
         ret = -errno;
     } else if (written != to_write) {
         /* even though EAGAIN is an errno value that could be set
            by write() in some cases, none of them apply here.  So, this return
            value can be clearly identified when debugging and suggests the
-           caller that it may try to call vibraror_on() again */
+           caller that it may try to call vibrator_on() again */
         ret = -EAGAIN;
     } else {
         ret = 0;
@@ -73,6 +73,14 @@ static int sendit(unsigned int timeout_ms)
     return ret;
 }
 
+static int sendit(unsigned int timeout_ms)
+{
+    char value[TIMEOUT_STR_LEN]; /* large enough for millions of years */
+
+    snprintf(value, sizeof(value), "%u", timeout_ms);
+    return write_value(THE_DEVICE, value);
+}
+
 static int vibra_on(vibrator_device_t* vibradev __unused, unsigned int timeout_ms)
 {
     /* constant on, up to maximum allowed time */
@@ -84,6 +92,43 @@ static int vibra_off(vibrator_device_t* vibradev __unused)
     return sendit(0);
 }
 
+static const char LED_DEVICE[] = "/sys/class/leds/vibrator";
+
+static int write_led_file(const char *file, const char *value)
+{
+    char file_str[50];
+
+    snprintf(file_str, sizeof(file_str), "%s/%s", LED_DEVICE, file);
+    return write_value(file_str, value);
+}
+
+static int vibra_led_exists()
+{
+    return !write_led_file("trigger", "transient");
+}
+
+static int vibra_led_on(vibrator_device_t* vibradev __unused, unsigned int timeout_ms)
+{
+    int ret;
+    char value[TIMEOUT_STR_LEN]; /* large enough for millions of years */
+
+    ret = write_led_file("state", "1");
+    if (ret)
+        return ret;
+
+    snprintf(value, sizeof(value), "%u\n", timeout_ms);
+    ret = write_led_file("duration", value);
+    if (ret)
+        return ret;
+
+    return write_led_file("activate", "1");
+}
+
+static int vibra_led_off(vibrator_device_t* vibradev __unused)
+{
+    return write_led_file("activate", "0");
+}
+
 static int vibra_close(hw_device_t *device)
 {
     free(device);
@@ -92,7 +137,15 @@ static int vibra_close(hw_device_t *device)
 
 static int vibra_open(const hw_module_t* module, const char* id __unused,
                       hw_device_t** device __unused) {
-    if (!vibra_exists()) {
+    bool use_led;
+
+    if (vibra_exists()) {
+        ALOGD("Vibrator using timed_output");
+        use_led = false;
+    } else if (vibra_led_exists()) {
+        ALOGD("Vibrator using LED trigger");
+        use_led = true;
+    } else {
         ALOGE("Vibrator device does not exist. Cannot start vibrator");
         return -ENODEV;
     }
@@ -109,8 +162,13 @@ static int vibra_open(const hw_module_t* module, const char* id __unused,
     vibradev->common.version = HARDWARE_DEVICE_API_VERSION(1,0);
     vibradev->common.close = vibra_close;
 
-    vibradev->vibrator_on = vibra_on;
-    vibradev->vibrator_off = vibra_off;
+    if (use_led) {
+        vibradev->vibrator_on = vibra_led_on;
+        vibradev->vibrator_off = vibra_led_off;
+    } else {
+        vibradev->vibrator_on = vibra_on;
+        vibradev->vibrator_off = vibra_off;
+    }
 
     *device = (hw_device_t *) vibradev;