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Michael Brown a39b111684 Automatically select between the "10" and "16" variants of command set, 18 years ago
..
arch/i386 Avoid draining the keyboard buffer during gateA20_set(). It shouldn't technically be necessary, because the "enable A20" command requires only that the keyboard controller is ready to accept input (i.e. that its input buffer is empty), and shouldn't also require that the keyboard is ready to send output (i.e. that its output buffer is also empty). See http://www.smsc.com/main/tools/io-bios/42i.pdf section 3.1 ("Command Invocation") for a justification. 18 years ago
bin Merged mcb30-realmode-redesign back to HEAD 19 years ago
commandline Added "clear" command 18 years ago
config Ignore buildserial-related files. 19 years ago
core Added clear_setting() 18 years ago
crypto Added "name" field to digest algorithms 18 years ago
doc Documented the link stages 19 years ago
drivers Automatically select between the "10" and "16" variants of command set, based on the device size. 18 years ago
hci/mucurses - implemented cursor retreat function (_wcursback) as a core function 18 years ago
include Automatically select between the "10" and "16" variants of command set, based on the device size. 18 years ago
interface/pxe We don't actually have a stdio.h header file. Our printf() functions are defined in vsprintf.h. (This may change, since vsprintf.h is a non-standard name, but for now it's the one to use.) 18 years ago
net Request all the options that we're prepared to do anything with. 18 years ago
proto We don't actually have a stdio.h header file. Our printf() functions are defined in vsprintf.h. (This may change, since vsprintf.h is a non-standard name, but for now it's the one to use.) 18 years ago
tests Typo 18 years ago
util Always update the PnP checksum, even if the ident string is not being set. 18 years ago
.cvsignore Merged mcb30-realmode-redesign back to HEAD 19 years ago
Config Removed vestigal FILO code 18 years ago
Makefile Do no evil. :) 18 years ago
Makefile.housekeeping Make VERSION_MAJOR for gPXE be 0 18 years ago
README.cvs Merged this file into HEAD 19 years ago
README.pixify Initial revision 19 years ago
config.h Does anyone still use 9600 baud? 18 years ago
doxygen.cfg Add include/gpxe as a directory to scan. 18 years ago

README.pixify

This file documents the driver changes needed to support use as part
of a PXE stack.

PROPER WAY
==========

1. The probe() routine.

There are three additional fields that need to be filled in the nic
structure: ioaddr, irqno and irq.

ioaddr is the base I/O address and seems to be for information only;
no use will be made of this value other than displaying it on the
screen.

irqno must be the IRQ number for the NIC. For PCI NICs this can
simply be copied from pci->irq.

irq is a function pointer, like poll and transmit. It must point to
the driver's irq() function.

2. The poll() routine.

This must take an additional parameter: "int retrieve". Calling
poll() with retrieve!=0 should function exactly as before. Calling
poll() with retrieve==0 indicates that poll() should check for the
presence of a packet to read, but must *not* read the packet. The
packet will be read by a subsequent call to poll() with retrieve!=0.

The easiest way to implement this is to insert the line
if ( ! retrieve ) return 1;
between the "is there a packet ready" and the "fetch packet" parts of
the existing poll() routine.

Care must be taken that a call to poll() with retrieve==0 does not
clear the NIC's "packet ready" status indicator, otherwise the
subsequent call to poll() with retrieve!=0 will fail because it will
think that there is no packet to read.

poll() should also acknowledge and clear the NIC's "packet received"
interrupt. It does not need to worry about enabling/disabling
interrupts; this is taken care of by calls to the driver's irq()
routine.

Etherboot will forcibly regenerate an interrupt if a packet remains
pending after all interrupts have been acknowledged. You can
therefore get away with having poll() just acknolwedge and clear all
NIC interrupts, without particularly worrying about exactly when this
should be done.

3. The irq() routine.

This is a new routine, with prototype
void DRIVER_irq ( struct nic *nic, irq_action_t action );
"action" takes one of three possible values: ENABLE, DISABLE or FORCE.
ENABLE and DISABLE mean to enable/disable the NIC's "packet received"
interrupt. FORCE means that the NIC should be forced to generate a
fake "packet received" interrupt.

If you are unable to implement FORCE, your NIC will not work when
being driven via the UNDI interface under heavy network traffic
conditions. Since Etherboot's UNDI driver (make bin/undi.zpxe) is the
only program known to use this interface, it probably doesn't really
matter.


QUICK AND DIRTY WAY
===================

It is possible to use the system timer interrupt (IRQ 0) rather than a
genuine NIC interrupt. Since there is a constant stream of timer
interrupts, the net upshot is a whole load of spurious "NIC"
interrupts that have no effect other than to cause unnecessary PXE API
calls. It's inefficient but it works.

To achieve this, simply set nic->irqno=0 in probe() and point nic->irq
to a dummy routine that does nothing. Add the line
if ( ! retrieve ) return 1;
at the beginning of poll(), to prevent the packet being read (and
discarded) when poll() is called with retrieve==0;


UNCONVERTED DRIVERS
===================

Drivers that have not yet been converted should continue to function
when not used as part of a PXE stack, although there will be a
harmless compile-time warning about assignment from an incompatible
pointer type in the probe() function, since the prototype for the
poll() function is missing the "int retrieve" parameter.