Re: Regression in 5.5.0-rc6 for FL2000 USB 3.0 to VGA adapter

[Johan Hovold <johan@kernel.org>]

On Sun, Jan 19, 2020 at 12:52:40AM +0100, Steve Markgraf wrote:
> Hi list,
> 
> Commit 3e4f8e21c4f27bcf30a48486b9dcc269512b79ff "USB: core: fix check
> for duplicate endpoints" is causing a regression with devices based on
> the Fresco Logic FL2000 chip, i.e. it is totally unusable.
>
> The issue was first reported on the osmocom-sdr mailing list [1] and I
> can reproduce it on my machine with 5.5.0-rc6, with rc5 everything is
> working fine. By reverting the commit mentioned above, it is working as
> well.

Thanks for the detailed report.

> When connecting the device with rc6, I see the following dmesg output:
> https://steve-m.de/files/fl2000_dmesg.txt
> 
> The output of lsusb -v:
> https://steve-m.de/files/fl2000_lsusb.txt
> 
> Output of the Windows tool "USB Device Tree Viewer":
> https://steve-m.de/files/fl2000_usbtreeview.txt
> 
> Output of the USB-IF USB 3.0 Chapter 9 tests with a version from around
> the time the FL2000 was released to market (passing):
> https://steve-m.de/files/fl2000_chapter9.html
> 
> By looking at the lsusb output, it almost seems like a descriptor
> parsing issue, that now causes trouble after introducing the duplicate
> endpoint testing.

Looks like you indeed have two interfaces (0 and 1) claiming the same
endpoints (0x01 and 0x81), so the new sanity check is working as
intended.

I just took a quick look at the libosmo-fl2k code and it appears that
you claim both interfaces but never set alternate setting 1 for
interface 0, which would enable those endpoints.

Could you see if that's all that's needed to get your application
working again?

Johan