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authorAndrey Konovalov <andreyknvl@google.com>2020-05-07 20:06:56 +0300
committerFelipe Balbi <balbi@kernel.org>2020-05-14 12:30:17 +0300
commit97df5e5758f7d1dd0ca97e3210696818fc45bdb3 (patch)
tree33060c1f81e52b4651c2bde89eb275aef8578361 /Documentation
parent17ff3b72e742192f11e3136174ac4eafb50e38d4 (diff)
downloadlinux-97df5e5758f7d1dd0ca97e3210696818fc45bdb3.tar.xz
usb: raw-gadget: fix gadget endpoint selection
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>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/usb/raw-gadget.rst5
1 files changed, 2 insertions, 3 deletions
diff --git a/Documentation/usb/raw-gadget.rst b/Documentation/usb/raw-gadget.rst
index 9e78cb858f86..4af8b1f15574 100644
--- a/Documentation/usb/raw-gadget.rst
+++ b/Documentation/usb/raw-gadget.rst
@@ -27,9 +27,8 @@ differences are:
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).
+4. Raw Gadget explicitly exposes information about endpoints addresses and
+ capabilities allowing a user to write UDC-agnostic gadgets.
5. Raw Gadget has ioctl-based interface instead of a filesystem-based one.