I'm finding the documentation for accessing device memory/registers in
Solaris cryptic to say the least; I'd welcome some clarification. I'd
like to map device register, memory, and PCI Config space into driver
memory space and access it like memory. The Solaris documentation
implies this can't be done, but I find that hard to believe.
Chapter 7 of Writing Device Drivers says that device memory/registers
must be mapped in using ddi_regs_map_setup() then accessed using the
ddi_getX/ddi_putX routines. These access routines can look after
ordering and endianness for me. There is no option offered for me to
just access the regions as mapped memory and deal with any such issues
myself.
However, later chapters explain how I can support mapping device
memory/registers to user space in response to an mmap() call, so it
seems that user processes are allowed to access device memory/registers
as memory. Hard to believe that user processes are allowed to do it
while kernel drivers aren't, but that's what the book says.
Things get yet more cryptic and puzzling in the 'Alternate Device Access
Interfaces' section later in Chapter 7. This says that there are
alternative ways of accessing devices which work in specific
configurations if I don't mind reduced portability. For memory mapped
devices, the ddi_getX and ddi_putX can be used as alternatives to the
standard device access interfaces. Since those ARE the standard
interfaces, this paragraph appears to be nonsense; I suspect this is
meant to cover what I'm looking for, but is hopelessly confused.
This section goes on to talk about special functions for accessing I/O
space and PCI Configuration Space, mentioning alternative routines which
appear to be analogous to the standard routines, and have to be used in
the same ways as the standard routines. Why would I use these
alternatives which reduce my portability when they don't appear to be
any easier or more convenient to use than the standard fully-portable
routines? I must be missing something here as well.
In summary: my device has memory, registers, and config space which
appear in the processors' physical memory map. Does Solaris support
mapping these into kernel memory and accessing them like memory? I'll
look after any size/alignment/ordering/endian problems myself. If this
is supported, how do I do it and is there any documentation anywhere
which covers it?
Many Thanks,
jjf
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