Hi all,
myself and AnilKumar Vaddineni had continued a kernelnewbies thread in
private for a couple of mails and I just thought it should probably go
back to the list, in case anyone else wanted to read/contribute.
-kev
----- Forwarded message from -----
Date: Wed, 14 May 2003 11:15:42 +0100
To: AnilKumar Vaddineni <anilkumar_vaddineni@adp.com>
Subject: Re: Help needed regarding Network Device Drivers
Hi Anil,
[snip]
> I have seen the code of ne2k-pci.c but couldn't understand some
> piece of code in ne2k_pci_init_one function. The piece of code is
> given below.
I'm not entirely sure what it's doing here either, but I can make some
guesses:
> /* Do a preliminary verification that we have a 8390. */
> {
> int regd;
> outb(E8390_NODMA+E8390_PAGE1+E8390_STOP, ioaddr+E8390_CMD);
> regd = inb(ioaddr + 0x0d);
> outb(0xff, ioaddr + 0x0d);
> outb(E8390_NODMA+E8390_PAGE0, ioaddr + E8390_CMD);
'ioaddr' looks to be just a variable that addresses the device. To get
specific functions, the driver addresses specific registers on the
device, which it finds by adding offsets (the E8390_ macros) to
'ioaddr'.
I can't make out what the above is doing, but I reckon the E8390_
macros, in drivers/net/8390.h, should answer that.
> inb(ioaddr + EN0_COUNTER0); /* Clear the counter by reading.*/
> if (inb(ioaddr + EN0_COUNTER0) != 0) {
> outb(reg0, ioaddr);
> outb(regd, ioaddr + 0x0d); /* Restore the old
> values. */
> goto err_out_free_res;
> }
> }
All it's doing here is clearing a counter (of what I'm not sure), then
making sure the counter actually has been cleared. If the counter is
not clear, he goes to some error handling code (err_out_free_res); if
the counter is clear the code just continues on to the next step.
> I didn't get why the above code is written? If you know that, then could you
> please explain step by step? If not, can you refer to some site or book?
I think it's just to make sure that the module is being loaded for the
correct device, in case the user/system mistakenly tries to use this
module for some other device.
> In the function call given below, is the value for second argument is fixed
> to a particular device?
>
> request_region (ioaddr, NE_IO_EXTENT, DRV_NAME)
Because of the NE_ prefix, I'd guess that it's fixed to the ne2k
driver/device, but I can't find where the macro is defined. I'll take a
closer look later, but if you find it in the meantime could you let me
know?
> Where can we get the hardware manual for a particular network card? Do you
> have one? If yes, can you please send it?
No idea where you'd get that. I think manufacturers are fairly
secretive about such things.
hope that's of some use
-kev
----- End forwarded message -----
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