On Tue, Dec 20, 2016 at 10:02 AM, roboknight <[email protected]> wrote:

At the underlined point, I believe ep->desc is NULL because using the
kernel and an arm objdump variant,
>
> I located the assembly that is causing the NULL dereference.  Inside of
> usb_endpoing_dir_out, it tries to
> dereference ep->desc, but ep->desc must be NULL otherwise things would
> likely go swimmingly.  The problem
> is, I don't know what would cause ep->desc == NULL?  Whatever causes this
> (and it might be related to
> a function called "usb_gadget_ep_match_desc") I'd like to know because
> knowing might tell me how to fix
> whatever it is I'm doing wrong or maybe patch the code so that things
> might work.
>
> I'm hoping someone knowledgeable about am335x USB can help here, or maybe
> let me know what I'm missing
> in my HID configuration.  The above configuration steps may not work,
> however, some python code I had previously
> also fails to function.  It might even be possible that I just need to use
> the regular HID driver and not one based on
> libcomposite.
>
> Thanks for reading this.  Hopefully there are some answers.
>

So, I'm not a USB composite framework expert. I only started reading about
it last night for another reason. A lot of what you're stating in your last
couple paragraphs here do not make sense to me. What I'm reading from your
post is that the end point descriptor must be NULL. but you're not sure why
it's NULL . . .yadda yadda yadda . . .That should not be true.

My first impression after looking through that code is user error. Simply
because a function that's being used requires a valid end point descriptor
reference as an argument, and that argument is NULL. Which tells me that
whole "object" was never instantiated in the first place.

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