device/xhci: Add helper method to iterate over xhci_supported_protocl

There is some boilerplate required to iterate over the USB supported
protocol structs. Encapsulate all the in a method to make the callers
simpler.

BUG=b:154756391
TEST=Built test trembyle.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I401f10d242638b0000ba697573856d765333dca0
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43352
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/device/xhci.c

@@ -1,9 +1,10 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
-#include <device/xhci.h>
+#include <arch/mmio.h>
 #include <console/console.h>
 #include <device/pci_def.h>
-#include <arch/mmio.h>
+#include <device/xhci.h>
+#include <string.h>
 
 union xhci_ext_caps_header {
 	uint32_t val;
@@ -75,6 +76,42 @@ enum cb_err xhci_for_each_ext_cap(const struct device *device, void *context,
 	return CB_SUCCESS;
 }
 
+struct supported_usb_cap_context {
+	void *context;
+	void (*callback)(void *context, const struct xhci_supported_protocol *data);
+};
+
+static void xhci_supported_usb_cap_handler(void *context, const struct xhci_ext_cap *cap)
+{
+	const struct xhci_supported_protocol *data;
+	struct supported_usb_cap_context *internal_context = context;
+
+	if (cap->cap_id != XHCI_ECP_CAP_ID_SUPP)
+		return;
+
+	data = &cap->supported_protocol;
+
+	if (memcmp(data->name, "USB ", 4)) {
+		printk(BIOS_DEBUG, "%s: Unknown Protocol: %.*s\n", __func__,
+		       (int)sizeof(data->name), data->name);
+		return;
+	}
+
+	internal_context->callback(internal_context->context, data);
+}
+
+enum cb_err xhci_for_each_supported_usb_cap(
+	const struct device *device, void *context,
+	void (*callback)(void *context, const struct xhci_supported_protocol *data))
+{
+	struct supported_usb_cap_context internal_context = {
+		.context = context,
+		.callback = callback,
+	};
+
+	return xhci_for_each_ext_cap(device, &internal_context, xhci_supported_usb_cap_handler);
+}
+
 void xhci_print_supported_protocol(const struct xhci_supported_protocol *supported_protocol)
 {
 	printk(BIOS_DEBUG, "xHCI Supported Protocol:\n");

src/include/device/xhci.h

@@ -52,6 +52,14 @@ enum cb_err xhci_for_each_ext_cap(const struct device *device, void *context,
 				  void (*callback)(void *context,
 						   const struct xhci_ext_cap *cap));
 
+/**
+ * Helper method that iterates over only the USB supported capabilities structures in the
+ * xHCI Extended Capabilities List.
+ */
+enum cb_err xhci_for_each_supported_usb_cap(
+	const struct device *device, void *context,
+	void (*callback)(void *context, const struct xhci_supported_protocol *data));
+
 void xhci_print_supported_protocol(const struct xhci_supported_protocol *supported_protocol);
 
 #endif /* __DEVICE_XHCI_H__ */