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Date: Wed, 18 Oct 2006 09:34:30 -0400
To: Paul B Schroeder <pschroeder@uplogix.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Exar quad port serial
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References: <1160068402.29393.7.camel@rupert> <20061005173628.GB30993@csclub.uwaterloo.ca> <45357CA1.80706@uplogix.com>
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From: Lennart Sorensen <lsorense@csclub.uwaterloo.ca>
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On Tue, Oct 17, 2006 at 08:00:17PM -0500, Paul B Schroeder wrote:
> Sorry for the late response..  Here is a fuller explanation.  Maybe 
> somebody out there has a better solution:
> 
> This is on our "Envoy" boxes which we have, according to the documentation, 
> an "Exar ST16C554/554D Quad UART with 16-byte Fifo's".  The box also has 
> two other "on-board" serial ports and a modem chip.
> 
> The two on-board serial UARTs were being detected along with the first two 
> Exar UARTs.  The last two Exar UARTs were not showing up and neither was 
> the modem.
> 
> This patch was the only way I could the kernel to see beyond the standard 
> four serial ports and get all four of the Exar UARTs to show up.
> 
> I hope this explains it well enough..

I suspect all you have to do might be to change how many ports it looks
for.  The default max ports is 4 I believe on many kernel versions.

Look for CONFIG_SERIAL_8250_NR_UARTS and
CONFIG_SERIAL_8250_RUNTIME_UARTS in the kernel config.

If that doesn't work and you do need a special driver, at least label it
with more detail like 'for exar st16c554 quad uart' or 'for envoy board'
or whatever makes it clear which hardware it is for.  I use exar pci
uarts (exar XR17d15[248] chips) which work fine already with the 8250
driver, or optionally with the jsm driver with a small change to the
list if pci identifiers.  THey of course would not work with your driver
since they are completely different exar chips (even though one is also
a quad uart, although 64byte fifo).

--
Len Sorensen
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