[Libdlo] DL vendor descriptor separate from config desc?

[Bernie Thompson]

Hi Andrew,

Thanks for posting about this - I hadn't yet seen a device with the
DisplayLink vendor descriptor hung off one of the configuration
descriptors, instead of the main device descriptor.

Can you email a dump of this device's USB topology - e.g. how many
configurations, and is it configuration #1 that has the DisplayLink
vendor descriptor in the extended area?

Actually, if you'd be willing to do up a patch to look first at the
device descriptor and if that's not there, then alternatively at the
(active) configuration descriptor, and can verify it works on that
device, we can push the patch downstream.

Yes, total_len would be better as u16 to catch errors. The philosophy
of udlfb related to these descriptors is to be tolerant of the
unexpected - maybe log something, but go ahead anyway (especially as
there are many older devices that don't have the descriptors at all).

Thanks again for the problem report on this device,
Bernie
http://plugable.com/

On Mon, Dec 13, 2010 at 10:10 AM, Andrew Kephart <akephart at akephart.org> wrote:
> During initialization, udlfb tries to pull a vendor-specific descriptor
> (0x5F) from the DL device, but on my device that particular info is
> embedded in the config descriptor.  Are there DL devices where that
> descriptor is independent of the config descriptor?
>
> Also, total_len (in dlfb_parse_vendor_descriptor) is declared u8, which
> may mask usb_get_descriptor errors.
>
> -andrew
>
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