RE: Specifying properly the PCI driver model on all linux archite

Patrick Lerda (LERDA@microprocess.com)
Tue, 2 Nov 1999 17:00:45 +0100

In my opinion the best way to implement ioremap() is with a physical memory
pointer as argument,
not a PCI bus memory pointer. But no specification exists, and the different
answers are not clear.
This question is fundamental on architectures like PREP PowerPC where all
memory spaces are
different and need a translation.

The specification of base_address[] is missing too, and need to be defined.
I think using the physical
address for base_address is the best way.

Physical memory is the only memory space with a different segment for all
space available:
SDRAM memory, PCI memory, PCI IO memory... With this definition ioremap
don't change on
x86 platform and can be used to get a virtual memory pointer an a PCI IO
space. I think this
is the right way.

Functions like readl() or writel() can't in my opinion be compatible with
ioremap(). ioremap() returns
a virtual memory pointer, and if an indirect access must be used to access
PCI memory, an other
programming model must be used... The file IO-mapping.txt is obsolete...

I agree with you Bret, we must clarify and write this documentation.

Patrick LERDA

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