[PATCH 3/3] usb: gadget: uvc: Allow disabling of interrupt endpoint

Daniel Scally
2022-12-05T14:38:18Z

The f_uvc code includes an interrupt endpoint against the VideoControl
interface. According to section 2.4.2 of the UVC specification however
this endpoint is optional in at least some cases:

"This endpoint is optional, but may be mandatory under certain
conditions"

The conditions enumerated are whether...

1. The device supports hardware triggers
2. The device implements any AutoUpdate controls
3. The device implements any Asynchronous controls

As all of those things are implementation dependent, this endpoint
might be unnecessary for some users. Check whether the user has
requested it be disable via configfs and don't proceed with its
instantiation if so.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
---
drivers/usb/gadget/function/f_uvc.c | 42 ++++++++++++++++++-----------
drivers/usb/gadget/function/uvc.h | 1 +
2 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index 49b7231742d6..76ec84d3a5fd 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -79,7 +79,7 @@ static struct usb_interface_descriptor uvc_control_intf = {
.bDescriptorType = USB_DT_INTERFACE,
.bInterfaceNumber = UVC_INTF_VIDEO_CONTROL,
.bAlternateSetting = 0,
- .bNumEndpoints = 1,
+ .bNumEndpoints = 0,
.bInterfaceClass = USB_CLASS_VIDEO,
.bInterfaceSubClass = UVC_SC_VIDEOCONTROL,
.bInterfaceProtocol = 0x00,
@@ -290,14 +290,16 @@ uvc_function_set_alt(struct usb_function *f, unsigned interface, unsigned alt)
if (alt)
return -EINVAL;

- uvcg_info(f, "reset UVC interrupt endpoint\n");
- usb_ep_disable(uvc->interrupt_ep);
+ if (!uvc->disable_interrupt_ep) {
+ uvcg_info(f, "reset UVC interrupt endpoint\n");
+ usb_ep_disable(uvc->interrupt_ep);

- if (!uvc->interrupt_ep->desc)
- if (config_ep_by_speed(cdev->gadget, f, uvc->interrupt_ep))
- return -EINVAL;
+ if (!uvc->interrupt_ep->desc)
+ if (config_ep_by_speed(cdev->gadget, f, uvc->interrupt_ep))
+ return -EINVAL;

- usb_ep_enable(uvc->interrupt_ep);
+ usb_ep_enable(uvc->interrupt_ep);
+ }

if (uvc->state == UVC_STATE_DISCONNECTED) {
memset(&v4l2_event, 0, sizeof(v4l2_event));
@@ -375,7 +377,8 @@ uvc_function_disable(struct usb_function *f)
uvc->state = UVC_STATE_DISCONNECTED;

usb_ep_disable(uvc->video.ep);
- usb_ep_disable(uvc->interrupt_ep);
+ if (!uvc->disable_interrupt_ep)
+ usb_ep_disable(uvc->interrupt_ep);
}

/* --------------------------------------------------------------------------
@@ -523,8 +526,10 @@ uvc_copy_descriptors(struct uvc_device *uvc, enum usb_device_speed speed)
control_size = 0;
streaming_size = 0;
bytes = uvc_iad.bLength + uvc_control_intf.bLength
- + uvc_interrupt_ep.bLength + uvc_control_cs_ep.bLength
- + uvc_streaming_intf_alt0.bLength;
+ + uvc_control_cs_ep.bLength + uvc_streaming_intf_alt0.bLength;
+
+ if (!uvc->disable_interrupt_ep)
+ bytes += uvc_interrupt_ep.bLength;

if (speed == USB_SPEED_SUPER) {
bytes += uvc_ss_control_comp.bLength;
@@ -569,7 +574,8 @@ uvc_copy_descriptors(struct uvc_device *uvc, enum usb_device_speed speed)
uvc_control_header->bInCollection = 1;
uvc_control_header->baInterfaceNr[0] = uvc->streaming_intf;

- UVC_COPY_DESCRIPTOR(mem, dst, &uvc_interrupt_ep);
+ if (!uvc->disable_interrupt_ep)
+ UVC_COPY_DESCRIPTOR(mem, dst, &uvc_interrupt_ep);
if (speed == USB_SPEED_SUPER)
UVC_COPY_DESCRIPTOR(mem, dst, &uvc_ss_control_comp);

@@ -656,12 +662,16 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
(opts->streaming_maxburst + 1));

/* Allocate endpoints. */
- ep = usb_ep_autoconfig(cdev->gadget, &uvc_interrupt_ep);
- if (!ep) {
- uvcg_info(f, "Unable to allocate control EP\n");
- goto error;
+ if (!opts->disable_interrupt_ep) {
+ ep = usb_ep_autoconfig(cdev->gadget, &uvc_interrupt_ep);
+ if (!ep) {
+ uvcg_info(f, "Unable to allocate interrupt EP\n");
+ goto error;
+ }
+ uvc->interrupt_ep = ep;
+ uvc_control_intf.bNumEndpoints = 1;
}
- uvc->interrupt_ep = ep;
+ uvc->disable_interrupt_ep = opts->disable_interrupt_ep;

if (gadget_is_superspeed(c->cdev->gadget))
ep = usb_ep_autoconfig_ss(cdev->gadget, &uvc_ss_streaming_ep,
diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 48b71e04c2b1..0d0ef9b90b1a 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -149,6 +149,7 @@ struct uvc_device {
struct usb_ep *interrupt_ep;
struct usb_request *control_req;
void *control_buf;
+ bool disable_interrupt_ep;

unsigned int streaming_intf;

--
2.34.1