gpio: Setup udev monitor before exporting pin

This will get rid of race condition that may lead to
missing udev event after exporting gpio pin.
Udev event monitor is now created before export.

Change-Id: Ifbad613252243c24cb03ed1765d3d947d244f56a

diff --git a/src/interface/peripheral_interface_gpio.c b/src/interface/peripheral_interface_gpio.c
index 0a916aadfddde8f12710b7caab2e31dad79c22be..850711da3b9edb82cc1463bc060a5f6625c55546 100644 (file)
--- a/src/interface/peripheral_interface_gpio.c
+++ b/src/interface/peripheral_interface_gpio.c
@@ -20,67 +20,78 @@
 #include "peripheral_interface_gpio.h"
 #include "peripheral_interface_common.h"
 
-static int __gpio_wait_for_udev(int pin)
+static int __gpio_create_udev_monitor(struct udev **udev, struct udev_monitor **monitor)
 {
-       struct udev *udev;
-       struct udev_monitor *monitor;
-       struct udev_device *dev;
-       struct pollfd pfd;
-       char gpio_name[MAX_BUF_LEN];
+       struct udev *_udev = NULL;
+       struct udev_monitor *_monitor = NULL;
        int ret = -EIO;
 
-       udev = udev_new();
-       if (!udev) {
+       _udev = udev_new();
+       if (!_udev) {
                _E("Cannot create udev");
-               return ret;
+               goto error;
        }
 
-       monitor = udev_monitor_new_from_netlink(udev, "udev");
-       if (!monitor) {
+       _monitor = udev_monitor_new_from_netlink(_udev, "udev");
+       if (!_monitor) {
                _E("Cannot create udev monitor");
-               udev_unref(udev);
-               return ret;
+               goto error;
        }
 
-       ret = udev_monitor_filter_add_match_subsystem_devtype(monitor, "gpio", NULL);
+       ret = udev_monitor_filter_add_match_subsystem_devtype(_monitor, "gpio", NULL);
        if (ret < 0) {
                _E("Failed to add monitor filter");
-               goto out;
+               goto error;
        }
 
-       ret = udev_monitor_enable_receiving(monitor);
+       ret = udev_monitor_enable_receiving(_monitor);
        if (ret < 0) {
                _E("Failed to enable udev receiving");
-               goto out;
+               goto error;
        }
 
+       *udev = _udev;
+       *monitor = _monitor;
+
+       return 0;
+
+error:
+       udev_monitor_unref(_monitor);
+       udev_unref(_udev);
+       return ret;
+}
+
+static int __gpio_wait_for_udev(struct udev_monitor *monitor, int pin)
+{
+       struct udev_device *dev;
+       struct pollfd pfd;
+       char gpio_name[MAX_BUF_LEN];
+
        pfd.fd = udev_monitor_get_fd(monitor);
        pfd.events = POLLIN;
 
        snprintf(gpio_name, MAX_BUF_LEN, "gpio%d", pin);
 
        for (int cnt = 0; cnt < 10; cnt++) {
+               _D("poll iteration");
                if (poll(&pfd, 1, 100) < 0) {
                        _E("Failed to watch udev monitor");
-                       goto out;
+                       return -EIO;
                }
 
                dev = udev_monitor_receive_device(monitor);
                if (dev) {
                        if (strcmp(udev_device_get_sysname(dev), gpio_name) == 0) {
                                _D("udev for %s is initialized", gpio_name);
-                               ret = 0;
-                               goto out;
+                               udev_device_unref(dev);
+                               return 0;
                        }
+                       udev_device_unref(dev);
                }
        }
        _E("Time out");
 
-out:
-       udev_monitor_unref(monitor);
-       udev_unref(udev);
-
-       return ret;
+       return 0;
 }
 
 int peripheral_interface_gpio_export(int pin)
@@ -88,27 +99,55 @@ int peripheral_interface_gpio_export(int pin)
        RETVM_IF(pin < 0, PERIPHERAL_ERROR_INVALID_PARAMETER, "Invalid gpio pin");
 
        int ret;
-       int fd;
+       int fd = -1;
        int length;
        char buf[MAX_BUF_LEN] = {0, };
+       struct udev *udev = NULL;
+       struct udev_monitor *monitor = NULL;
+
+       ret = __gpio_create_udev_monitor(&udev, &monitor);
+       if (ret != 0) {
+               _E("Failed to create udev monitor");
+               goto out;
+       };
 
        fd = open("/sys/class/gpio/export", O_WRONLY);
-       IF_ERROR_RETURN(fd < 0);
+       if (fd < 0) {
+               _E("open() failed: %m");
+               ret = PERIPHERAL_ERROR_IO_ERROR;
+               goto out;
+       }
 
        length = snprintf(buf, MAX_BUF_LEN, "%d", pin);
        ret = write(fd, buf, length);
-       IF_ERROR_RETURN(ret != length, close(fd));
+       if (ret != length) {
+               _E("write() failed: %m");
+               ret = PERIPHERAL_ERROR_IO_ERROR;
+               goto out;
+       }
 
        ret = close(fd);
-       IF_ERROR_RETURN(ret != 0);
+       if (ret != 0) {
+               _E("close() failed: %m");
+               ret = PERIPHERAL_ERROR_IO_ERROR;
+               goto out;
+       }
 
-       ret = __gpio_wait_for_udev(pin);
+       ret = __gpio_wait_for_udev(monitor, pin);
        if (ret < 0) {
                _E("device nodes are not writable");
-               return PERIPHERAL_ERROR_IO_ERROR;
+               ret = PERIPHERAL_ERROR_IO_ERROR;
+               goto out;
        }
 
-       return PERIPHERAL_ERROR_NONE;
+out:
+       if (fd != -1)
+               close(fd);
+
+       udev_monitor_unref(monitor);
+       udev_unref(udev);
+
+       return ret;
 }
 
 int peripheral_interface_gpio_unexport(int pin)