[uml-devel] [ link to patch] resurrecting the uml-hcd

["James McMechan" <james_mcmechan@hotmail.com>]

I am attempting to resurrect the uml-hcd driver
this version is based off of the gadget/dummy_hcd.c driver.

I am aiming at a 2.6.12.2 target where it will be used.
I have forward ported it to 2.6.17.6 for testing and hopefully
eventual inclusion.

This patch has a #PLATFORM to deal with the issues between
2.6.17.6/2.6.12.2 since platform_register... is not present in older
kernels and the new kernels don't work with the older registration.

For some reason the usb core is not sending hub urbs to my hcd
all the control seems to run through hub_control and hub_status_data
both of which are not checked before calling and so segfaults the kernel
if not present rather than queuing a control urb to get the
status as I would have expected...

Now I realize, that in hub_control I can assemble a urb out of the data
presented and call my enqueue method, but it looks like that would
be unusually dense of me, since it appears that there should already be
some way to get the urbs.

Notes:
I found that core/message.c does not include asm/scatterlist.h
it appears to assume that linux/pci.h has the scatterlist stuff,
but since UML has no PCI at all pci.h does not include it.
I just added the scatterlist.h should I have removed pci.h?

On 2.6.17.6 it segfaults in the core at hub.c:2251 dev_dbg
where udev->bus->controller->driver->name is used without checking
if driver == NULL which it was in my version.  I have not figured out
where that driver is supposed to be set since the controller appears to
be created in the usb core somewhere...
This patch now checks for that.

Does anyone know where bus->controller->driver is supposed to be set?

uml-hcd is currently partly operational
I can enumerate the device, libusb will talk to it.
Control URBs seem to go back and forth.
and report status back correctly.

I have walked through the usbmon output on the host and the hub simulation
is producing the same status in the same order as the host does
the host appears to produce urbs for its root hub however.
under uml usbmon does not show up in /sys/kernel/debug so
I have not been able to test it there, my current spew level dev_info dumps
all the hub control/status to my console.

Your thoughts are welcome, I would hate to have to fall back to creating a
virtual proc files system that just forwards all the libusb calls down to 
the
host OS.  This was working a few years ago and it looks (from dummy_hcd.c
and usbip) that it should be possible here. I know it was possible to write
a complete usb from userspace without requiring a stub driver back in
the bad old days of 2.4.18...

No doubt this version takes may liberties with the core and driver model
if you could point out some of the more obvious ones to me,
I still was thinking about the automatic interrupt urb submission when last
this was current.

The patch can be fetched from 
http://mysite.verizon.net/james.mcmechan/uml-hcd.2.6.17.6.patch
or bzipped as 
http://mysite.verizon.net/james.mcmechan/uml-hcd.2.6.17.6.patch.bz2
it is 1104 lines long & 31K in size so I stuck it on a web page.

Enjoy,

James McMechan



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