MBOX_HEXDUMP_MAX_LEN
touser = kzalloc(MBOX_HEXDUMP_MAX_LEN + 1, GFP_KERNEL);
while (l < MBOX_HEXDUMP_MAX_LEN) {
ret = simple_read_from_buffer(userbuf, count, ppos, touser, MBOX_HEXDUMP_MAX_LEN);