test_write
static inline int __always_unused test_write(struct v4l2_subdev *sd, u8 reg, u8 val)
static void test_write(const char *path, char *buf, int buf_size,
static int test_write(const char *path, const char *buf, size_t size,
ssize_t test_write(int fd, const void *buf, size_t count)