Index for Section 9r

Alphabetical listing for B

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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
  addr
      Specifies the address of the device registers or memory.

  length
      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.

  ptr 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 handle to a valid
       system physical address

    ·  Call the PHYS_TO_KSEG routine to convert the valid system physical
       address to a kernel-unmapped virtual 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.

Index for Section 9r

Alphabetical listing for B

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