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List:       e1000-devel
Subject:    Re: [E1000-devel] regarding e1000
From:       "Veeraiyan, Ayyappan" <ayyappan.veeraiyan () intel ! com>
Date:       2007-06-21 17:47:25
Message-ID: E35F4F4D7F6C9E4E826FEC1F86CEF58304026DC1 () orsmsx412 ! amr ! corp ! intel ! com
[Download RAW message or body]

I am ccing the e1000-delvel list where many people from Intel and outside can add \
their thoughts..

> > but i never see it setting up deive registers through the read*/write* 
> > to actually signal the device to start the transfer.

If I understand your question correctly, and in simplified view, the driver allocates \
buffers and sets up the descriptors (in Rx side) and then inform the device to start \
the DMA operation by writing to the tail register (RDT).

In both Tx and Rx cases, driver writes to tail (TDD/RDT) which signals the device \
that the buffers are ready for DMA operation. After that, device starts the DMA \
operation. For more info you can refer the SDM available in e1000.sf.net.

Ayyappan

________________________________________
From: Devvrat Tripathi [mailto:tripathidevvrat@gmail.com] 
Sent: Thursday, June 21, 2007 7:33 AM
To: aveerani@users.sourceforge.net
Subject: regarding e1000

respected sir,

I wanted to understand the working of the e1000 driver and i could not understand how \
does the driver signal the device to start a dma data transfer. Actually i wanted to \
log all the IO operations to any device in the system and for that i was logging \
calls to read*/write* and in*/out* and dma_unmap_* for a reasonably accurate idea of \
when and how much data actually flows to and from the devices. When i looked at the \
traces i found i saw that though the unmap functions are called alot of times by the \
e1000 driver but i never see it setting up deive registers through the read*/write* \
to actually signal the device to start the transfer. I guess there is something wrong \
in my approach. Can you suggest me where am i going wrong or is there some other \
method apart from write* or out*  which i need to  log. 

regards

devvrat 

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