Design issues Keyspan serial PCI driver

Geert Uytterhoeven geert at
Sun Aug 15 01:30:44 EST 1999

On Fri, 13 Aug 1999, Otto Moerbeek wrote:
> after some struggling I now have a very first working version of the
> Keyspan SX
> serial card driver, but I do not think the code I wrote is ready for
> publishing. To make a neat driver I have some design issues I want to
> share with you. Hopefully this will help me making the right decisions
> for the real driver.
> The Keyspan SX cards use a PLX9050 as PCI bridge to connect to an
> ST16C654 UART. I found some patches for char/serial.c that support the
> UART directly. So this part of the problem was solved easily.
> But Keyspan choose to map the UART to PCI memory space using the 9050,
> not PCI I/O space. Furthermore, for some unknown reason, the registers
> of the UART are separated 0x80 apart. Since char/serial.c uses I/O
> instructions to access the UART, I had to hack the driver to use readb()
> and friends. I am also multiplying the offset to compensate for the
> strange offsets.

Please also post your message on linux-kernel at, since this is
of interest not only for Linux/PPC development.

> The good news of course is, if I can resolve the above issues, I have a
> driver that can access both I/O based and memory based PCI cards. The
> start of proper PCI serial card support in the standard serial driver?

That would be great!



Geert Uytterhoeven                     Geert.Uytterhoeven at
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium

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