Tim Waugh (
Wed, 27 Oct 1999 19:58:56 +0100 (BST)

On Tue, 19 Oct 1999, Gilles Noyer wrote:

> I saw that the version 2.3.22 work on writing in ECP mode.
> but is it possible to read on ECP mode using FIFO or DMA ?

The reason it isn't at the moment possible is this: I haven't found a
datasheet that describes how to change from ECP mode to SPP mode without
data loss.

The issue is that when you change from ECP mode to SPP mode, the FIFO is
cleared. If there were a way of telling the chipset not to receive any
more data to the FIFO, then it would be possible to ensure that no data is
lost, and all would be well. I *suspect* that setting the strobe bit in
CTR will do the trick, but I can't test it here and I haven't seen that
mentioned in any datasheet.

The code to do ECP reads through the FIFO is in parport_pc.c, it's just
not used.

If anyone knows whether the strobe thing works reliably, or knows a better
way that I've overlooked, I'd certainly like to know.


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This archive was generated by hypermail 2.0b3 on Wed 27 Oct 1999 - 15:49:34 EDT