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| author | Andrey Konovalov <andreyknvl@google.com> | 2020-05-07 19:06:58 +0200 |
|---|---|---|
| committer | Felipe Balbi <balbi@kernel.org> | 2020-05-14 12:30:18 +0300 |
| commit | 61d2658db48af0c563d126cccc5c1105137b1ec9 (patch) | |
| tree | 03c61388a0ef230de689a82d977510b79361a085 | |
| parent | c61769bd4777a922952aed0d042a2572e5bd9b74 (diff) | |
| download | lwn-61d2658db48af0c563d126cccc5c1105137b1ec9.tar.gz lwn-61d2658db48af0c563d126cccc5c1105137b1ec9.zip | |
usb: raw-gadget: documentation updates
Mention the issue with fixed UDC addresses.
Links external examples and test suite.
Add more implmenetation details and potential improvements.
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
| -rw-r--r-- | Documentation/usb/raw-gadget.rst | 30 |
1 files changed, 28 insertions, 2 deletions
diff --git a/Documentation/usb/raw-gadget.rst b/Documentation/usb/raw-gadget.rst index 3b3d78e850b2..68d879a8009e 100644 --- a/Documentation/usb/raw-gadget.rst +++ b/Documentation/usb/raw-gadget.rst @@ -49,10 +49,36 @@ The typical usage of Raw Gadget looks like: Raw Gadget and react to those depending on what kind of USB device needs to be emulated. +Note, that some UDC drivers have fixed addresses assigned to endpoints, and +therefore arbitrary endpoint addresses can't be used in the descriptors. +Nevertheles, Raw Gadget provides a UDC-agnostic way to write USB gadgets. +Once a USB_RAW_EVENT_CONNECT event is received via USB_RAW_IOCTL_EVENT_FETCH, +the USB_RAW_IOCTL_EPS_INFO ioctl can be used to find out information about +endpoints that the UDC driver has. Based on that information, the user must +chose UDC endpoints that will be used for the gadget being emulated, and +properly assign addresses in endpoint descriptors. + +You can find usage examples (along with a test suite) here: + +https://github.com/xairy/raw-gadget + +Internal details +~~~~~~~~~~~~~~~~ + +Currently every endpoint read/write ioctl submits a USB request and waits until +its completion. This is the desired mode for coverage-guided fuzzing (as we'd +like all USB request processing happen during the lifetime of a syscall), +and must be kept in the implementation. (This might be slow for real world +applications, thus the O_NONBLOCK improvement suggestion below.) + Potential future improvements ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- Reporting more events (suspend, resume, etc.) through - USB_RAW_IOCTL_EVENT_FETCH. +- Report more events (suspend, resume, etc.) through USB_RAW_IOCTL_EVENT_FETCH. - Support O_NONBLOCK I/O. + +- Support USB 3 features (accept SS endpoint companion descriptor when + enabling endpoints; allow providing stream_id for bulk transfers). + +- Support ISO transfer features (expose frame_number for completed requests). |