On Wed, Dec 21, 2016 at 1:56 PM, roboknight <robokni...@gmail.com> wrote:
> > > On Tuesday, December 20, 2016 at 3:27:44 PM UTC-5, William Hermans wrote: >> >> >> >> On Tue, Dec 20, 2016 at 10:02 AM, roboknight <robok...@gmail.com> 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. >> > > The yadda yadda yadda was kind of the point. I actually have looked into > it further and the only way that reference would actually be null is if the > autoepconfig function couldn't choose any available endpoint because none > of them matched the correct criteria. I'm not sure where I'm supposed to > SET UP the appropriate criteria, hence the question, and the details. > >> >> 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. >> > those objects aren't "instantiated". They are actually endpoints that are > "built-in" (you can see one for full-speed, high-speed, and now > super-speed). One of the endpoints is supposed to get selected based on an > appropriate description. Mine probably doesn't match or I haven't set one, > hence it doesn't work. But I don't see anywhere where I can actually > SPECIFY the necessary things in configfs... Maybe you just can't build a > HID device with configfs right now? Or maybe something changed. Either > way, I'm researching the answer to that question so I can figure out what I > really need to do. Maybe there is another way I can configure a HID > driver, not using configfs. > > The things I was able to do in the 3.13.xx kernel don't seem to work with > this kernel either, or I don't have them set up correctly, hence I figured > the "new" or current method was to use configfs. But maybe this isn't the > case. > > I have tried to get the "latest" from the TI repo, and the results are the > same. So I'm guessing that my kernel configuration was probably okay, but > somehow I'm not doing something right with configfs, or configfs doesn't > work for HID devices yet (I don't know if I believe that, but its > possible). At any rate, I've not managed to get it working yet. > Yeah that's all I was really saying. Sometimes *things* like to be done in a certain order, or maybe a configfs step that was required was missed ? Theres a LWN article I was reading the other day, that seems to be pretty full of information. However, the "walk-thru" only talks about re-implementing the mass storage gadget using USB composite. https://lwn.net/Articles/395712/ I've also seen a few presentation type PDF's out there. I do not really know enough about the framework to know how useful these are though. Passed that, I have not yet seen one for HiD. Although . . . you know what, I think DR. Phil Polstra did a presentation on emulating a keyboard using HiD USB device, and I do think he used configfs . . . However he may have used an older kernel as well. I'll tell you what though, even though I'm not necessarily interested in creating an HiD device. I have interest in this whole composite framework. SO I'll do some searching on my own, and let you know what I find. I may even just start out with an HiD "thing" just to get my feet wet. Maybe you've seen these already ? I'm not sure if any, or all of this is already know to you, but here goes . . . Matt Porter: http://events.linuxfoundation.org/sites/events/files/slides/USB%20Gadget%20Configfs%20API_0.pdf Andrzej Pietrasiewicz: https://events.linuxfoundation.org/sites/events/files/slides/LinuxConNA-Make-your-own-USB-gadget-Andrzej.Pietrasiewicz.pdf Additional documentation / example code: http://lxr.free-electrons.com/source/Documentation/usb/gadget_hid.txt -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CALHSORrSC5RsWQ5rdcMg%3D4SuOmgvw2h4YFAMLhQTozGO6q1ajQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
