DDE Linux26 in the Hurd

Björn Döbel doebel at os.inf.tu-dresden.de
Wed Jan 27 13:51:16 CET 2010

Hash: SHA1

>>> 1. dde linux26 doesn't support multiple PCI buses. Unfortunately, my virtual
>>> machine has two PCI buses: bus 0 and bus 2. Now I have to hardcode the bus
>>> numbers in the code. Do you have plan to support multiple PCI buses?
>> Our approach is to provide the application with a single logical PCI bus
>> within DDEKit and have a management component that parses the real PCI
>> bus and multiplexes accesses. Have a look at l4/pkg/l4io. As in most of
>> the cases you only use one device within a DDEKit-based application, we
>> did not see any real benefit of supporting multiple PCI buses in DDE.
> OK, I see your point and I believe that one device doesn't use two buses, but I
> didn't see how a logical PCI bus is mapped to a physical one. ddekit_pci_init calls
>         err = l4io_pci_find_device(~0, ~0, start, &l4dev);
> to search for buses, which calls a RPC to the kernel, but every DDEKIT
> application starts with 0. I don't see where is your management component and
> how it chooses the right bus for the device.

The L4IO server scans all PCI devices at startup. DDE applications use
l4io_pci_find_device() to iterate over all the devices and assign them a
local/logical PCI ID. So, yes, for a DDE application it always looks
like there is only one PCI bus (bus 0) with a continuous range of devices.

>>> 2. DDE Linux26 doesn't support sound card drivers.
>>> Does DDE Linux26 support the block device and character device?
>> The answer for all points is that this is usually a matter of adding the
>> corresponding Linux code and maybe some glue code. We did this for
>> character, sound and block devices to a certain point. However, there is
>> no releasable code, yet.
> So are you still working on supporting character, sound and block devices?

Yes. In our current (unreleased) versions, input devices work. Sound and
block support has not been driven to an acceptible point, yet. There is
also a USB package in the public SVN, fyi.

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