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You can google for "RTL8139(A/B) programming
guide", it's pretty much comprehensive and detailed.
Roman Mashak
----- Original Message -----
Sent: Tuesday, February 13, 2007 7:45
PM
Subject: Re: RTL8139: TX buffers
On 2/13/07, Roman
Mashak <mrv@xxxxxxxxxxxxx>
wrote:
Hello,
I
kept exploring the sources of rtl8139 NIC and stuck with the weird spot
in
'rtl8139_hw_start()' (same both in a 2.4.x and 2.6.x). I don't post
here
very detailed code, as I assume everybody here has access to linux
source
tree :)
do u have any docs, which explains this driver.? can you share with
us?
because, i haven't written driver for network
cards.
Ashok
...
/*
init Tx buffer DMA addresses */
for (i = 0; i < NUM_TX_DESC;
i++)
RTL_W32_F (TxAddr0 +
(i * 4), tp->tx_bufs_dma + (tp->tx_buf[i]
-
tp->tx_bufs));
RTL_W32_F is a macro exposing into
'writel(tp->tx_bufs_dma +
(tp->tx_buf[i] - tp->tx_bufs), ...)'
call. By the time of this call 'tx_buf'
has been properly initialised and
contains addresses of 4 TX descriptors.
As I understand 'tx_bufs_dma'
holds the physical address of DMA memory,
while 'tx_bufs' - kernel
virtual address.
What I can't figure out is the point
of this calculations: tp->tx_bufs_dma
+ (tp->tx_buf[i] -
tp->tx_bufs)
Why can't we simply have 'tp->tx_bufs_dma + (i *
4)' ?
Thanks in advance.
---
Best regards,
Roman
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