transmit_cmd_struct
volatile struct transmit_cmd_struct *xmit_cmds[NUM_XMIT_BUFFS];
p->xmit_cmds[i] = (struct transmit_cmd_struct *)ptr; /*transmit cmd/buff 0*/
ptr = (char *) ptr + sizeof(struct transmit_cmd_struct);
memset((char *)(p->xmit_cmds[i]) ,0, sizeof(struct transmit_cmd_struct));