BADADDR(9r)BADADDR(9r)NAMEBADADDR - 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 con‐
figured, 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 call‐
ing 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 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 accessi‐
ble or a nonzero value if the data is not accessible.
BADADDR(9r)