Function 62, subfunctions 4,5,6 - read PCI-register.
Parameters:
- eax = 62 - function number
- bl = 4 - read byte
- bl = 5 - read word
- bl = 6 - read dword
- bh = number of PCI-bus
- ch = dddddfff, where ddddd = number of the device on the bus,
fff = function number of device
- cl = number of register (must be even for bl=5,
divisible by 4 for bl=6)
Returned value:
- eax = -1 - error (access to PCI is disabled or parameters
are not supported); otherwise
- al/ax/eax (depending on requested size) contains the data;
the other part of register eax is destroyed
Remarks:
- Previously low-level access to PCI for applications must be
enabled by subfunction 12 of function 21.
- Access mechanism 2 supports only 16 devices on a bus and ignores
function number. To get access mechanism use subfunction 2.
- Some registers are standard and exist for all devices, some are
defined by the concrete device. The list of registers of the
first type can be found e.g. in famous
Interrupt List by Ralf Brown
(http://www.pobox.com/~ralf/files.html,
ftp://ftp.cs.cmu.edu/afs/cs/user/ralf/pub/);
registers of the second type must be listed
in the device documentation.