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Re: [Qemu-devel] Large USB patch

From: Fabrice Bellard
Subject: Re: [Qemu-devel] Large USB patch
Date: Sun, 23 Apr 2006 17:02:34 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913


Could you make a small patch containing just the bug fixes of the state machine ?

Concerning your API changes, I am relunctant to include them now, but my mind can evolve. An API change that I would consider as very useful could be to be able to make asynchronous USB I/Os to avoid blocking QEMU while doing host USB I/Os.



address@hidden wrote:
Hello everybody,

I have extended the USB support for Qemu. The patch is included and
compiles just fine against todays cvs repository. As explained below,
this patch touches 15 different files, which makes it not so easy to
keep it applying on that very fast developing project. Thats why I would
ask you to test it quickly and apply it to cvs as soon as possible.

With this patch applied I could detect a USB Epson Scanner and a USB
Epson Printer from Windows 98 + XP and I could even print pages with
the printer (see known problems below).

reasons for this patch:
I was looking for a way to address my USB printer with windows while
working on linux. As I started the work I had to recognize that my
printer was not even detected under qemu. So I started to work on it.

changes I made:
First I eliminated all potential error sources, which could be avoided.
One of these sources where the

1. usb-hub - which I transfered to an extra file usb-hub.c, then I
added the usb-libusb.c devices directly to the UHCI controller this
introduced the changes of 2)
2. I enhanced the usb add device potentialities so that you should be
able to add a device to the UHCI controller. This device can be a usb
hub or a usb device. Behind this device you can add another hub or
device ... (remember this feature is now theoretically possible but not
tested yet), this let to a new usb syntax:
#$ qemu -usb controller=uhci,busnum=001 device=host:2:3,addto=001:001
(the short form is:
#$ qemu -usb controller=uhci -usb device=host:2:3)
so you can build up a complete usb tree.
3. I changed the usb_generic_handle_packet() function and implemented a
state machine, which is able to handle the usb packets correct.
4. I changed the linux standard usb-host library to libusb. I personally
will always prefer a portable solution if possible.
5. I changed large parts of usb-libusb.c. Some changes were made because
I found the source very awkward, some others because I fixed errors and
some because I changed the general usb api (see item 2).
6. I tried to join as many usb functions as possible to the usb related
files. So that hopefully nobody has to change 15 files again.
7. I made minor changes to usb-uhci - mainly I applied the new api and
changed the handling of special messages like usb_reset or usb_attach
8. I made the necessary changes to usb-hid.c and usb-hub.c
9. I wrote a lot of source comments

this patch breaks some things:
Sorry guys but I could not fix all of it, so I need your help, I didn't
want to destroy anybodys work, but the new api makes it necessary to
change some files:
1. usb-linux.c and usb-bsd.c will not work without adoption of the new api
2. I did not test usb-hid and usb-hub

known problems:
1. under linux the uhci controller reports an error if no usb device is
2. the printer and the scanner are recognized under Windows 98/XP and
Linux, but the scanner goes into STALL state as soon as a packet in
usb_write_bulk() or usb_read_bulk()
3. the libusb usb_host_reset() function does not work as expected and I
don't know why (i have commented out this part of the source)
4. the printer stops printing on large images and is then in a state,
where it will not resume his work (probably a timing issue)

With kind regards,
Tino H. Seifert


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