How to list network devices in NASM (custom OS) - networking

Question

I have a custom, DOS-like OS built in NASM completely (no C code). It is very modest (it does have a FAT file system, few apps, is in real mode, etc.) I want to write a command that will list all the network devices (network cards) that are currently connected.
My assumptions go like this: I will need to write a driver for the network card (I'd put it manually inside kernel for simplicity, so dynamic loading would NOT exist), but it would be enough for that driver to just provide the name of the card, the network card wouldn't actually need to work. How do I tell the OS to connect that function to precisely that one network card? This is what I'm in the blue about, I have no idea how the OS usually matches a piece of hardware to code (its driver(s)).

Answer 1

Since it appears from your comments that you have Dosbox supporting an NE2000 card then the code below should detect the presence of an NE2000 card (A port base of 0x300 is assumed). The code is a DOS COM program I wrote and should be compilable with a command like nasm ne2kchk.asm -fbin -o ne2kchk.com
NS_DATAPORT EQU 0x10 ; NatSemi-defined port window offset.
NE_DATAPORT EQU 0x10 ; NatSemi-defined port window offset.
NS_RESET EQU 0x1f ; Issue a read to reset, a write to clear.
NE1SM_START_PG EQU 0x20 ; First page of TX buffer
NE1SM_STOP_PG EQU 0x40 ; Last page +1 of RX ring
NESM_START_PG EQU 0x40 ; First page of TX buffer
NESM_STOP_PG EQU 0x80 ; Last page +1 of RX ring
E8390_CMD EQU 0x00 ; The command register (for all pages)
E8390_STOP EQU 0x01 ; Stop and reset the chip
E8390_START EQU 0x02 ; Start the chip, clear reset
E8390_RREAD EQU 0x08 ; Remote read
E8390_NODMA EQU 0x20 ; Remote DMA
E8390_PAGE0 EQU 0x00 ; Select page chip registers
E8390_PAGE1 EQU 0x40 ; using the two high-order bits
E8390_PAGE2 EQU 0x80
E8390_PAGE3 EQU 0xC0 ; Page 3 is invalid on the real 8390.
E8390_RXOFF EQU 0x20 ; EN0_RXCR: Accept no packets
E8390_TXOFF EQU 0x02 ; EN0_TXCR: Transmitter off
; Page 0 register offsets.
EN0_CLDALO EQU 0x01 ; Low byte of current local dma addr RD
EN0_STARTPG EQU 0x01 ; Starting page of ring bfr WR
EN0_CLDAHI EQU 0x02 ; High byte of current local dma addr RD
EN0_STOPPG EQU 0x02 ; Ending page +1 of ring bfr WR
EN0_BOUNDARY EQU 0x03 ; Boundary page of ring bfr RD WR
EN0_TSR EQU 0x04 ; Transmit status reg RD
EN0_TPSR EQU 0x04 ; Transmit starting page WR
EN0_NCR EQU 0x05 ; Number of collision reg RD
EN0_TCNTLO EQU 0x05 ; Low byte of tx byte count WR
EN0_FIFO EQU 0x06 ; FIFO RD
EN0_TCNTHI EQU 0x06 ; High byte of tx byte count WR
EN0_ISR EQU 0x07 ; Interrupt status reg RD WR
EN0_CRDALO EQU 0x08 ; low byte of current remote dma address RD
EN0_RSARLO EQU 0x08 ; Remote start address reg 0
EN0_CRDAHI EQU 0x09 ; high byte, current remote dma address RD
EN0_RSARHI EQU 0x09 ; Remote start address reg 1
EN0_RCNTLO EQU 0x0a ; Remote byte count reg WR
EN0_RCNTHI EQU 0x0b ; Remote byte count reg WR
EN0_RSR EQU 0x0c ; rx status reg RD
EN0_RXCR EQU 0x0c ; RX configuration reg WR
EN0_TXCR EQU 0x0d ; TX configuration reg WR
EN0_COUNTER0 EQU 0x0d ; Rcv alignment error counter RD
EN0_DCFG EQU 0x0e ; Data configuration reg WR
EN0_COUNTER1 EQU 0x0e ; Rcv CRC error counter RD
EN0_IMR EQU 0x0f ; Interrupt mask reg WR
EN0_COUNTER2 EQU 0x0f ; Rcv missed frame error counter RD
PORT_BASE EQU 0x300 ; Default base port
[BITS 16]
org 0x100
section .text
start:
push cs
pop ds
; Probe for NE2000 card
; Try non destructive test first
mov dx, PORT_BASE+E8390_CMD
in al, dx
cmp al, 0xff
jz .s_notfound
; Attempt potentially destuctive tests
mov al, E8390_NODMA | E8390_PAGE1 | E8390_STOP
mov dx, PORT_BASE+E8390_CMD
out dx, al ; Receive alignment error counter
mov dx, PORT_BASE+EN0_COUNTER0
in al, dx
mov cl, al ; Save to REGD (CL)
mov al, 0xff
out dx, al
mov al, E8390_NODMA | E8390_PAGE0
mov dx, PORT_BASE+E8390_CMD
out dx, al
mov dx, PORT_BASE+EN0_COUNTER0
in al, dx ; Clear the counter by reading.
test al, al
jz .s_found ; If al is clear then card was found
; Card not found
.s_notfound:
xchg al, cl ; Temporarily save al to avoid clobber
out dx, al
mov ah, 0x09
mov dx, notfound_str
int 0x21
xchg al, cl ; Restore al. al = error value to return
jmp .s_exit
; Card found
.s_found:
mov ah, 0x09
mov dx, found_str
int 0x21
xor al, al ; Clear the error code
; exit with al = errcode
.s_exit:
mov ah, 0x4C
int 0x21
notfound_str db "NE2000 not found", 0x0a, 0x0d, "$"
found_str db "NE2000 found", 0x0a, 0x0d, "$"
The code above is an adaptation of "C" code that I found in the Debian nictool code available here . It can be found in the file ne2k-diags.c. It seems more information (datasheets) are available for the rtl8019 which is a clone of the NE2000. The 8390NIC that is at the heart of these devices is documented here. The 8390 documentation discusses how to send and receive data. An excerpt of the "C" code that I based mine on was:
printf("Checking the ethercard at %#3x.\n", port_base);
{ int regd;
long ioaddr = port_base;
outb_p(E8390_NODMA+E8390_PAGE1+E8390_STOP, ioaddr + E8390_CMD);
regd = inb_p(ioaddr + 0x0d);
printk(" Receive alignment error counter (%#lx) is %2.2x\n",
ioaddr + 0x0d, regd);
outb_p(0xff, ioaddr + 0x0d);
outb_p(E8390_NODMA+E8390_PAGE0, ioaddr + E8390_CMD);
inb_p(ioaddr + EN0_COUNTER0); /* Clear the counter by reading. */
if (inb_p(ioaddr + EN0_COUNTER0) != 0) {
outb(regd, ioaddr + 0x0d); /* Restore the old values. */
printk(" Failed initial NE2000 probe, value %2.2x.\n",
inb(ioaddr + EN0_COUNTER0));
} else
printk(" Passed initial NE2000 probe, value %2.2x.\n",
inb(ioaddr + EN0_COUNTER0));
}
The code above is the initial probe but there is more "C" code in the same file that tries to detect some of the specific variants and query the card signature.