drivers: usb: move UDC net_buf_data_cb implementation to USB common

Move it to USB common so that it can be used on the host side in the
future.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>

Author: jfischer-no

drivers/usb/common/CMakeLists.txt

@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: Apache-2.0
 
 add_subdirectory_ifdef(CONFIG_HAS_NRFX nrf_usbd_common)
+add_subdirectory(buf)

drivers/usb/common/buf/CMakeLists.txt

@@ -0,0 +1,5 @@
+# Copyright Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()
+zephyr_library_sources_ifdef(CONFIG_UDC_DRIVER usb_buf.c)

drivers/usb/common/buf/usb_buf.c

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/net_buf.h>
+#include <zephyr/drivers/usb/udc_buf.h>
+
+static inline uint8_t *usb_pool_data_alloc(struct net_buf *const buf,
+					   size_t *const size, k_timeout_t timeout)
+{
+	struct net_buf_pool *const buf_pool = net_buf_pool_get(buf->pool_id);
+	struct k_heap *const pool = buf_pool->alloc->alloc_data;
+	void *b;
+
+	*size = UDC_ROUND_UP(*size);
+	b = k_heap_aligned_alloc(pool, UDC_BUF_ALIGN, *size, timeout);
+	if (b == NULL) {
+		*size = 0;
+		return NULL;
+	}
+
+	return b;
+}
+
+static inline void usb_pool_data_unref(struct net_buf *buf, uint8_t *const data)
+{
+	struct net_buf_pool *buf_pool = net_buf_pool_get(buf->pool_id);
+	struct k_heap *pool = buf_pool->alloc->alloc_data;
+
+	k_heap_free(pool, data);
+}
+
+const struct net_buf_data_cb net_buf_dma_cb = {
+	.alloc = usb_pool_data_alloc,
+	.unref = usb_pool_data_unref,
+};

drivers/usb/udc/udc_common.c

@@ -21,36 +21,6 @@
 #endif
 LOG_MODULE_REGISTER(udc, CONFIG_UDC_DRIVER_LOG_LEVEL);
 
-static inline uint8_t *udc_pool_data_alloc(struct net_buf *const buf,
-					   size_t *const size, k_timeout_t timeout)
-{
-	struct net_buf_pool *const buf_pool = net_buf_pool_get(buf->pool_id);
-	struct k_heap *const pool = buf_pool->alloc->alloc_data;
-	void *b;
-
-	*size = ROUND_UP(*size, UDC_BUF_GRANULARITY);
-	b = k_heap_aligned_alloc(pool, UDC_BUF_ALIGN, *size, timeout);
-	if (b == NULL) {
-		*size = 0;
-		return NULL;
-	}
-
-	return b;
-}
-
-static inline void udc_pool_data_unref(struct net_buf *buf, uint8_t *const data)
-{
-	struct net_buf_pool *buf_pool = net_buf_pool_get(buf->pool_id);
-	struct k_heap *pool = buf_pool->alloc->alloc_data;
-
-	k_heap_free(pool, data);
-}
-
-const struct net_buf_data_cb net_buf_dma_cb = {
-	.alloc = udc_pool_data_alloc,
-	.unref = udc_pool_data_unref,
-};
-
 static inline void udc_buf_destroy(struct net_buf *buf);
 
 UDC_BUF_POOL_VAR_DEFINE(udc_ep_pool,