[Linux-parport] EPP modes

Leopold Palomo-Avellaneda leo at alaxarxa.net
Wed Mar 5 05:31:40 EST 2008

A Dilluns 03 Març 2008, Adam Baker va escriure:
> On Monday 03 March 2008 10:22, Leopold Palomo-Avellaneda wrote:
> > Hi,
> >
> >
> >
> > I have realised that all the boxes that we have here using 2.6.18 (debian
> > kernel stock and 2.6.22) nones has EPP active. Also with kernels more
> > recent. Also, only in a lab of 7 different boxes, only one could support
> > EPP, when _ALL_  of them the bios claims to support it.
> >
> > So my question are:
> > Is this a problem of the driver? This driver is unmaintained?
> Short answer, you need to patch your kernel, as per the patch below
> (which is against 2.6.25-rc2 but this code hasn't changed in ages).
> Longer answer: A long time ago (~ 10 years), Intel produced a chipset that
> included broken EPP support. The Linux parport driver was written to detect
> such a chipset and disable EPP support on it. Unfortunately the test that
> was written gives false positives for many current chipsets and no-one
> seems to know exactly what the problem hardware was, let alone have a
> sample of it to see if a better test can be written. After such a long time
> it is probably appropriate to just remove the test (on average it does more
> harm than good) however you are correct in asserting the driver is
> unmaintained so no-one is bothering to fix it.
> In theory the way to get the change into mainline in that case is to post
> to LKML but you should then be prepared to test development kernels etc. so
> I haven't bothered. If you want to chase it up feel free to add


first of all thanks for the mail and I'm sorry for the delay in the answer. I 
took a lot of care with the mail and yesterday I was compiling some kernels. 
Testing it, with a debian stock kernel 2.6.24 patching the needed file. 
Howeber the result was unsuccessfully. I got the same results. :-(

But, I got and strange behaviour  and I couldn't reproduce it again, but maybe 
it could help. In the box I have connected the needed device, I always have 
had a lot of messages in the dmesg with:
parport0: FIFO is stuck
parport0: BUSY timeout (1) in compat_write_block_pio
parport0: FIFO is stuck
parport0: BUSY timeout (1) in compat_write_block_pio
parport0: FIFO is stuck
parport0: BUSY timeout (1) in compat_write_block_pio

then I remove the lp mod with rmmod -f lp

Then I remove ppdev and parport_pc.

When i modprobe parport_pc I got the EPP mode. Howeber, I have tried to repeat 
it but I couldn't. Probably I found some kind of "heissenbug".


what more? I couldn't get EPP mode in any dell box.

Any idea?



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