cec-funcs.h: static inlines to pack/unpack CEC messages

Hello Hans Verkuil,

The patch 50f7d5a65e5a: "[media] cec-funcs.h: static inlines to pack/unpack CEC messages" from Jun 17, 2016, leads to the following static checker warning:

	include/linux/cec-funcs.h:1154 cec_ops_set_osd_string()
	warn: setting length 'msg->len - 3' to negative one

include/linux/cec-funcs.h
1150 static inline void cec_ops_set_osd_string(const struct cec_msg *msg,
1151 __u8 *disp_ctl,
1152 char *osd)
1153 {
1154 unsigned int len = msg->len - 3;

The reason for this warning is that we know msg->len is at least 2 but this code assumes it is at least 3. There is a check in cec_received_msg() which ensures that it is not <= 1.

  1155  
  1156          *disp_ctl = msg->msg[2];
  1157          if (len > 13)
  1158                  len = 13;
  1159          memcpy(osd, msg->msg + 3, len);
  1160          osd[len] = '\0';
  1161  }

regards,
dan carpenter