Hi, Binyamin Sharet <bsharet@xxxxxxxxx> writes: >>>>> I think this will cause existing implementation over gadgetfs to fail >>>>> with this >>>>> special kernel (as now it will delegate everything all of the time). How >>>>> about >>>>> using a ioctl to configure it, but wrapping this ioctl with Kconfig? >>>>> This way >>>>> gadgetfs will operate as always unless a user activates "delegate all" >>>>> in runtime. >>>>> >>>>> Sounds reasonable? >>>> You mean a ep0 ioctl? Makes sense to me. Then we can add more features >>>> later. Perhaps just add a "Get supported features" IOCTL which returns >>>> a struct with 256 bits (4x uint64_t). I doubt we will ever need that >>>> many bits, but better safe than sorry, I guess. >>>> >>> Don't we need some "set feature" IOCTL as well? >> Why? Features are enabled at kernel compile time. Userspace issues ioctl >> to ask the kernel "which features do you have enabled for >> GadgetFS?". Note that we have a backwards compatibility problem here. If >> "which features do you have enabled for GadgetFS" ioctl fails, we will >> assume that kernel is older than the first kernel where this ioctl was >> added. >> >> To help userland a little more, we can make sure that, from now on, the >> ioctl itself is always enabled and bit0 out of the 256 bits we have MUST >> always be set. This means that "Forward all requests to userspace" >> feature has to be, at least, bit1. >> >> This mimics what USB descriptors where bit7 of config descriptor's >> bmAttributes must always be set. We're just using bit0 instead. >> > What I mean is - when the gadgetfs compiled with "Forward all requests to > userspace" feature, it should behave as before until an ep0 ioctl is issued > to actually enable this feature (e.g. forward the messages) otherwise, this > version of gadgetfs will break any current userspace application that uses > it. > Am I missing something? No, you're not. I misunderstood what you meant ;-) Yeah, I agree, we also need an IOCTL to enable specific features after discovering they exist. -- balbi
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