osf1 man page for badaddr

BADADDR(9r)															       BADADDR(9r)

NAME
       BADADDR - General: Probes the address during device autoconfiguration

SYNOPSIS
       int BADADDR(
	       caddr_t addr,
	       int length,
	       struct bus_ctlr_common *ptr );

ARGUMENTS
       Specifies  the  address of the device registers or memory.  Specifies the length (in bytes) of the data to be checked.  Valid values are 1,
       2, and 4 on 32-bit machines and 4 and 8 on 64-bit machines.  Specifies a pointer to a bus_ctlr_common structure. You cast this argument	as
       a pointer to either a bus or controller structure.

DESCRIPTION
       The  BADADDR  routine generates a call to a machine-dependent routine that does a read access check of the data at the supplied address and
       dismisses any machine check exception that may result from the attempted access. You call this routine to probe for memory or  I/O  devices
       at a specified address during device autoconfiguration.

NOTES
       You  can  use  BADADDR  in  device drivers that are statically configured into the kernel. However, you cannot use BADADDR if the driver is
       dynamically configured into the kernel.

       If you implement the driver to be both statically and dynamically configured, you can declare a variable and use it to control the call	to
       BADADDR.

       The following code fragment shows the use of such a variable used in the probe routine for the /dev/none driver:

       .  .  .

	    if (none_is_dynamic) {

	    /* Code to handle tasks associated with a dynamically *
	     * configured driver */

       .  .  .

	    }
	    else {

	   /* Code to handle tasks (including the call to BADADDR) *
	    * associated with a statically configured driver *
	    * including call to BADADDR 	   */
	   }

       .  .  .

       The  EISA  and  ISA buses do not generate a machine check when BADADDR performs a read access to a nonexistent location. These buses always
       return success when BADADDR performs a read access to their address space.

       For the PCI bus and the VMEbus, you must do the following before calling BADADDR: Call the iohandle_to_phys routine to convert the I/O han-
       dle to a valid system physical address Call the PHYS_TO_KSEG routine to convert the valid system physical address to a kernel-unmapped vir-
       tual address Call the BADADDR routine, passing this kernel-unmapped virtual address as the first argument

RETURN VALUES
       The BADADDR routine returns the value 0 (zero) if the data is accessible or a nonzero value if the data is not accessible.

																       BADADDR(9r)