Autoconfiguration

The attach(9E) routine should perform the common initialization tasks that all devices require. Typically, these tasks include:

• Allocating per-instance state structures

• Registering device interrupts

• Mapping the device's registers

• Initializing mutex and condition variables

• Creating power-manageable components

• Creating minor nodes

See "attach(9E)" for code examples of these tasks.

Character device drivers create minor nodes of type S_IFCHR. This causes a character special file representing the node to eventually appear in the /devices hierarchy. Example 10-1 shows a character driver attach(9E) routine.

Example 10-1 Character Driver attach(9E) Routine

static int
xxattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
  switch (cmd) {
  case DDI_ATTACH:
allocate a state structure and initialize it.
map the device's registers.
add the device driver's interrupt handler(s).
initialize any mutexes and condition variables.
create power manageable components.
          /*
           * Create the device's minor node. Note that the node_type
           * argument is set to DDI_NT_TAPE.
           */
           if (ddi_create_minor_node(dip, "minor_name", S_IFCHR,
               minor_number, DDI_NT_TAPE, 0) == DDI_FAILURE) {
                  free resources allocated so far.
               /* Remove any previously allocated minor nodes */
               ddi_remove_minor_node(dip, NULL);
               return (DDI_FAILURE);
           }
           ...
           return (DDI_SUCCESS);    
case DDI_RESUME:
        For information, see Chapter 9, Power Management   
default:
        return (DDI_FAILURE);
      }
}