On 08/07/2017 11:15 AM, Jeff Webb wrote:
On 08/07/2017 10:08 AM, Jeff Webb wrote:
I am attempting to port legacy Xenomai 2.6.4 code to Xenomai 3.
In our current code base, we implement userspace drivers using
libpci, iopl, inb/outb, /dev/mem, and the pthread_intr_*_np
family of functions. Since the pthread_intr_*_np functions are
no longer part of Xenomai, I have been researching and
experimenting with the new UDD framework as a replacement.
Although documentation and examples are a little scarce, I have
found most of the information I need. I also used some
documentation on the Linux UIO framwork to fill in some gaps in
my knowledge. My preliminary conclusion is that using the UDD
framework would allow us to port our existing code base without
too much modification, but I still have a few remaining
questions.
I see the way that PCI device memory regions can be accessed
using mmap with UDD_MEM_PHYS mem_regions, but on some PCI devices
we also need to access I/O port regions, such as:
Region 0: Memory at f7102000 (32-bit, non-prefetchable) [size=128]
Region 1: I/O ports at b100 [size=128]
Region 2: I/O ports at b280 [size=4]
The UIO documentation recommends using the struct uio_info's port
field (an array of 'uio_port' structs) to pass information about
the I/O port regions associated with the device to userspace. I
did not see the equivalent of this functionality in the UDD
framework, and was wondering why it was omitted. What is the
recommended way of determining the ports associated with a device
when using a UDD driver? It seems like continuing to do this
using libpci and then somehow matching this up with the
corresponding UDD device would be messy and error-prone.
If no other support exists, perhaps I could use kmalloc to allocate a
UDD_MEM_LOGICAL region corresponding to each PCI I/O port region on the
card. The kernel UDD driver would then populate these regions with
the I/O addresses of the corresponding PCI I/O port regions. The
UDD_MEM_LOGICAL regions could then be read by the userspace driver
to determine the I/O address to use with inb/outb (and iopl).
Another way would be to pass the port I/O region addresses (and possibly sizes)
to userspace via explicit IOCTLs. If so, should the IOCTL numbers for such a
use case be standardized?
If there is no standard way to do this sort of thing, and if there are no
recommendations about how to do proceed, I'll just do what feels right in my
case, but I thought someone might have some experience or opinion on how this
should be done in the Xenomai UDD context, since the Linux UIO method of
passing port information is not available.
Thanks,
-Jeff
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