MSM_CAM_IOCTL_GET_PICTURE is a kernel call which runs the function
static int msm_get_pic(struct msm_sync *sync, void __user *arg)
I downloaded the kernel source for your device from the HTCdev and found the function defined in
drivers/media/video/msm/msm_camera-7x30.c
Could check what are the kernel messages when you take a picture?
adb shell su -c "dmesg"