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[Qemu-devel] ne2000 bug? buffer full/empty
From: |
Marcel Block |
Subject: |
[Qemu-devel] ne2000 bug? buffer full/empty |
Date: |
Tue, 27 Mar 2007 08:58:44 +0200 |
User-agent: |
Icedove 1.5.0.9 (X11/20061220) |
Hi qemu-devers,
this is my first post here, so please be kind :-)
i believe i found a bug in qemu's ne2000 code. i'm currently working on
a ne2000 driver for my little hobby-os and i'm having some troubles
getting it to receive any packets when running on qemu. but it works
fine on bochs and on _real_ ne2000-hardware (rtl8029-pci in my case).
i believe the case "current page register == boundary register" should
be interpreted as 'buffer empty' instead of 'buffer full'. this was
changed last year or so by dr. han zhu, i tried to send him a email but
it looks like the email-address he used back then is no longer available.
the current code looks like this: (hw/ne2000.c):
static int ne2000_buffer_full(NE2000State *s)
{
int avail, index, boundary;
index = s->curpag << 8;
boundary = s->boundary << 8;
if (index <= boundary)
avail = boundary - index;
else
avail = (s->stop - s->start) - (index - boundary);
if (avail < (MAX_ETH_FRAME_SIZE + 4))
return 1;
return 0;
}
that way qemu thinks the buffer is full if index==boundary. if i change
the "if(index <= boundary)" back to "if(index < boundary)" my driver
appears to work fine.
all the specs i read so far tend to initialize those two registers to
the same value. so it appears logical that index==boundary should be
interpreted as 'buffer empty'.
i'm waiting for your feedback :-)
best regards,
marcel block
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