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config | ||
core | ||
crypto | ||
doc | ||
drivers | ||
hci/mucurses | ||
include | ||
interface/pxe | ||
net | ||
proto | ||
tests | ||
util | ||
.cvsignore | ||
Config | ||
config.h | ||
doxygen.cfg | ||
Makefile | ||
Makefile.housekeeping | ||
README.cvs | ||
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.