[PATCH 4.4 15/46] USB: core: add helpers to retrieve endpoints

Greg Kroah-Hartman
2020-09-21T16:32:03Z

From: Johan Hovold <johan@kernel.org>

commit 66a359390e7e34f9a4c489467234b107b3d76169 upstream.

Many USB drivers iterate over the available endpoints to find required
endpoints of a specific type and direction. Typically the endpoints are
required for proper function and a missing endpoint should abort probe.

To facilitate code reuse, add a helper to retrieve common endpoints
(bulk or interrupt, in or out) and four wrappers to find a single
endpoint.

Note that the helpers are marked as __must_check to serve as a reminder
to always verify that all expected endpoints are indeed present. This
also means that any optional endpoints, typically need to be looked up
through separate calls.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/core/usb.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/usb.h | 35 ++++++++++++++++++++
2 files changed, 118 insertions(+)

--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -77,6 +77,89 @@ MODULE_PARM_DESC(autosuspend, "default a

/**
+ * usb_find_common_endpoints() -- look up common endpoint descriptors
+ * @alt: alternate setting to search
+ * @bulk_in: pointer to descriptor pointer, or NULL
+ * @bulk_out: pointer to descriptor pointer, or NULL
+ * @int_in: pointer to descriptor pointer, or NULL
+ * @int_out: pointer to descriptor pointer, or NULL
+ *
+ * Search the alternate setting's endpoint descriptors for the first bulk-in,
+ * bulk-out, interrupt-in and interrupt-out endpoints and return them in the
+ * provided pointers (unless they are NULL).
+ *
+ * If a requested endpoint is not found, the corresponding pointer is set to
+ * NULL.
+ *
+ * Return: Zero if all requested descriptors were found, or -ENXIO otherwise.
+ */
+int usb_find_common_endpoints(struct usb_host_interface *alt,
+ struct usb_endpoint_descriptor **bulk_in,
+ struct usb_endpoint_descriptor **bulk_out,
+ struct usb_endpoint_descriptor **int_in,
+ struct usb_endpoint_descriptor **int_out)
+{
+ struct usb_endpoint_descriptor *epd;
+ int i;
+
+ if (bulk_in)
+ *bulk_in = NULL;
+ if (bulk_out)
+ *bulk_out = NULL;
+ if (int_in)
+ *int_in = NULL;
+ if (int_out)
+ *int_out = NULL;
+
+ for (i = 0; i < alt->desc.bNumEndpoints; ++i) {
+ epd = &alt->endpoint[i].desc;
+
+ switch (usb_endpoint_type(epd)) {
+ case USB_ENDPOINT_XFER_BULK:
+ if (usb_endpoint_dir_in(epd)) {
+ if (bulk_in && !*bulk_in) {
+ *bulk_in = epd;
+ break;
+ }
+ } else {
+ if (bulk_out && !*bulk_out) {
+ *bulk_out = epd;
+ break;
+ }
+ }
+
+ continue;
+ case USB_ENDPOINT_XFER_INT:
+ if (usb_endpoint_dir_in(epd)) {
+ if (int_in && !*int_in) {
+ *int_in = epd;
+ break;
+ }
+ } else {
+ if (int_out && !*int_out) {
+ *int_out = epd;
+ break;
+ }
+ }
+
+ continue;
+ default:
+ continue;
+ }
+
+ if ((!bulk_in || *bulk_in) &&
+ (!bulk_out || *bulk_out) &&
+ (!int_in || *int_in) &&
+ (!int_out || *int_out)) {
+ return 0;
+ }
+ }
+
+ return -ENXIO;
+}
+EXPORT_SYMBOL_GPL(usb_find_common_endpoints);
+
+/**
* usb_find_alt_setting() - Given a configuration, find the alternate setting
* for the given interface.
* @config: the configuration to search (not necessarily the current config).
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -97,6 +97,41 @@ enum usb_interface_condition {
USB_INTERFACE_UNBINDING,
};

+int __must_check
+usb_find_common_endpoints(struct usb_host_interface *alt,
+ struct usb_endpoint_descriptor **bulk_in,
+ struct usb_endpoint_descriptor **bulk_out,
+ struct usb_endpoint_descriptor **int_in,
+ struct usb_endpoint_descriptor **int_out);
+
+static inline int __must_check
+usb_find_bulk_in_endpoint(struct usb_host_interface *alt,
+ struct usb_endpoint_descriptor **bulk_in)
+{
+ return usb_find_common_endpoints(alt, bulk_in, NULL, NULL, NULL);
+}
+
+static inline int __must_check
+usb_find_bulk_out_endpoint(struct usb_host_interface *alt,
+ struct usb_endpoint_descriptor **bulk_out)
+{
+ return usb_find_common_endpoints(alt, NULL, bulk_out, NULL, NULL);
+}
+
+static inline int __must_check
+usb_find_int_in_endpoint(struct usb_host_interface *alt,
+ struct usb_endpoint_descriptor **int_in)
+{
+ return usb_find_common_endpoints(alt, NULL, NULL, int_in, NULL);
+}
+
+static inline int __must_check
+usb_find_int_out_endpoint(struct usb_host_interface *alt,
+ struct usb_endpoint_descriptor **int_out)
+{
+ return usb_find_common_endpoints(alt, NULL, NULL, NULL, int_out);
+}
+
/**
* struct usb_interface - what usb device drivers talk to
* @altsetting: array of interface structures, one for each alternate