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2021-01-26usb: raw-gadget: update documentation and KconfigAndrey Konovalov
Update Raw Gadget documentation and Kconfig. Make the description more precise and clear, fix typos and grammar mistakes, and do other cleanups. Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Link: https://lore.kernel.org/r/f4c650c94ae2b910e38819d51109cd5f0b251a2a.1611429174.git.andreyknvl@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-05-14usb: raw-gadget: documentation updatesAndrey Konovalov
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>
2020-05-14usb: raw-gadget: support stalling/halting/wedging endpointsAndrey Konovalov
Raw Gadget is currently unable to stall/halt/wedge gadget endpoints, which is required for proper emulation of certain USB classes. This patch adds a few more ioctls: - USB_RAW_IOCTL_EP0_STALL allows to stall control endpoint #0 when there's a pending setup request for it. - USB_RAW_IOCTL_SET/CLEAR_HALT/WEDGE allow to set/clear halt/wedge status on non-control non-isochronous endpoints. Fixes: f2c2e717642c ("usb: gadget: add raw-gadget interface") Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Felipe Balbi <balbi@kernel.org>
2020-05-14usb: raw-gadget: fix gadget endpoint selectionAndrey Konovalov
Currently automatic gadget endpoint selection based on required features doesn't work. Raw Gadget tries iterating over the list of available endpoints and finding one that has the right direction and transfer type. Unfortunately selecting arbitrary gadget endpoints (even if they satisfy feature requirements) doesn't work, as (depending on the UDC driver) they might have fixed addresses, and one also needs to provide matching endpoint addresses in the descriptors sent to the host. The composite framework deals with this by assigning endpoint addresses in usb_ep_autoconfig() before enumeration starts. This approach won't work with Raw Gadget as the endpoints are supposed to be enabled after a set_configuration/set_interface request from the host, so it's too late to patch the endpoint descriptors that had already been sent to the host. For Raw Gadget we take another approach. Similarly to GadgetFS, we allow the user to make the decision as to which gadget endpoints to use. This patch adds another Raw Gadget ioctl USB_RAW_IOCTL_EPS_INFO that exposes information about all non-control endpoints that a currently connected UDC has. This information includes endpoints addresses, as well as their capabilities and limits to allow the user to choose the most fitting gadget endpoint. The USB_RAW_IOCTL_EP_ENABLE ioctl is updated to use the proper endpoint validation routine usb_gadget_ep_match_desc(). These changes affect the portability of the gadgets that use Raw Gadget when running on different UDCs. Nevertheless, as long as the user relies on the information provided by USB_RAW_IOCTL_EPS_INFO to dynamically choose endpoint addresses, UDC-agnostic gadgets can still be written with Raw Gadget. Fixes: f2c2e717642c ("usb: gadget: add raw-gadget interface") Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Felipe Balbi <balbi@kernel.org>
2020-03-15usb: gadget: add raw-gadget interfaceAndrey Konovalov
USB Raw Gadget is a kernel module that provides a userspace interface for the USB Gadget subsystem. Essentially it allows to emulate USB devices from userspace. Enabled with CONFIG_USB_RAW_GADGET. Raw Gadget is currently a strictly debugging feature and shouldn't be used in production. Raw Gadget is similar to GadgetFS, but provides a more low-level and direct access to the USB Gadget layer for the userspace. The key differences are: 1. Every USB request is passed to the userspace to get a response, while GadgetFS responds to some USB requests internally based on the provided descriptors. However note, that the UDC driver might respond to some requests on its own and never forward them to the Gadget layer. 2. GadgetFS performs some sanity checks on the provided USB descriptors, while Raw Gadget allows you to provide arbitrary data as responses to USB requests. 3. Raw Gadget provides a way to select a UDC device/driver to bind to, while GadgetFS currently binds to the first available UDC. 4. Raw Gadget uses predictable endpoint names (handles) across different UDCs (as long as UDCs have enough endpoints of each required transfer type). 5. Raw Gadget has ioctl-based interface instead of a filesystem-based one. Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Felipe Balbi <balbi@kernel.org>