[systemd-devel] [PATCH] accelerometer: Don't wait for new data from the sensor

[Bastien Nocera]

Instead of waiting for new data from the sensor, which might be
a long time coming, depending on the sensor device, ask the kernel
for the last state for that particular input device.
---
 src/udev/accelerometer/accelerometer.c | 33 ++++++---------------------------
 1 file changed, 6 insertions(+), 27 deletions(-)

diff --git a/src/udev/accelerometer/accelerometer.c b/src/udev/accelerometer/accelerometer.c
index 925d38d..32adf27 100644
--- a/src/udev/accelerometer/accelerometer.c
+++ b/src/udev/accelerometer/accelerometer.c
@@ -180,7 +180,7 @@ get_prev_orientation(struct udev_device *dev)
         return string_to_orientation(value);
 }
 
-#define SET_AXIS(axis, code_) if (ev[i].code == code_) { if (got_##axis == 0) { axis = ev[i].value; got_##axis = true; } }
+#define READ_AXIS(axis, var) { memzero(&abs_info, sizeof(abs_info)); r = ioctl(fd, EVIOCGABS(axis), &abs_info); if (r < 0) return; var = abs_info.value; }
 
 /* accelerometers */
 static void test_orientation(struct udev *udev,
@@ -189,10 +189,9 @@ static void test_orientation(struct udev *udev,
 {
         OrientationUp old, new;
         _cleanup_close_ int fd = -1;
-        struct input_event ev[64];
-        bool got_syn = false;
-        bool got_x = false, got_y = false, got_z = false;
+        struct input_absinfo abs_info;
         int x = 0, y = 0, z = 0;
+        int r;
         char text[64];
 
         old = get_prev_orientation(dev);
@@ -201,30 +200,10 @@ static void test_orientation(struct udev *udev,
         if (fd < 0)
                 return;
 
-        while (1) {
-                int i, r;
-
-                r = read(fd, ev, sizeof(struct input_event) * 64);
-
-                if (r < (int) sizeof(struct input_event))
-                        return;
-
-                for (i = 0; i < r / (int) sizeof(struct input_event); i++) {
-                        if (got_syn) {
-                                if (ev[i].type == EV_ABS) {
-                                        SET_AXIS(x, ABS_X);
-                                        SET_AXIS(y, ABS_Y);
-                                        SET_AXIS(z, ABS_Z);
-                                }
-                        }
-                        if (ev[i].type == EV_SYN && ev[i].code == SYN_REPORT)
-                                got_syn = true;
-                        if (got_x && got_y && got_z)
-                                goto read_dev;
-                }
-        }
+        READ_AXIS(ABS_X, x);
+        READ_AXIS(ABS_Y, y);
+        READ_AXIS(ABS_Z, z);
 
-read_dev:
         new = orientation_calc(old, x, y, z);
         snprintf(text, sizeof(text),
                  "ID_INPUT_ACCELEROMETER_ORIENTATION=%s", orientation_to_string(new));
-- 
2.0.0