change(usb/host): Remove data buffer headers from URBs

This commit removes the ability to reserve a header in the data buffer of an
allocated URB. The header was required for a now defunct implementation of a
synchronous USB Host library API. Thus, headers are no longer required in
URB data buffers.

components/usb/hub.c

@@ -938,7 +938,7 @@ esp_err_t hub_install(hub_config_t *hub_config)
     HUB_DRIVER_EXIT_CRITICAL();
     // Allocate Hub driver object
     hub_driver_t *hub_driver_obj = heap_caps_calloc(1, sizeof(hub_driver_t), MALLOC_CAP_DEFAULT);
-    urb_t *enum_urb = urb_alloc(sizeof(usb_setup_packet_t) + ENUM_CTRL_TRANSFER_MAX_DATA_LEN, 0, 0);
+    urb_t *enum_urb = urb_alloc(sizeof(usb_setup_packet_t) + ENUM_CTRL_TRANSFER_MAX_DATA_LEN, 0);
     if (hub_driver_obj == NULL || enum_urb == NULL) {
         return ESP_ERR_NO_MEM;
     }

components/usb/private_include/usb_private.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2023 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -43,7 +43,6 @@ struct urb_s {
     uint32_t hcd_var;
     // Host Lib Layer:
     void *usb_host_client;  // Currently only used when submitted to shared pipes (i.e., Device default pipes)
-    size_t usb_host_header_size; // USB Host may need the data buffer to have a transparent header
     bool usb_host_inflight; // Debugging variable, used to prevent re-submitting URBs already inflight
     // Public transfer structure. Must be last due to variable length array
     usb_transfer_t transfer;
@@ -76,15 +75,13 @@ typedef bool (*usb_proc_req_cb_t)(usb_proc_req_source_t source, bool in_isr, voi
  *
  * - Data buffer is allocated in DMA capable memory
  * - The constant fields of the URB are also set
- * - The data_buffer field of the URB is set to point to start of the allocated data buffer AFTER the header. To access
- *   the header, users need a negative offset from data_buffer.
+ * - The data_buffer field of the URB is set to point to start of the allocated data buffer.
  *
  * @param data_buffer_size Size of the URB's data buffer
- * @param header_size Size of header to put in front of URB's data buffer
  * @param num_isoc_packets Number of isochronous packet descriptors
  * @return urb_t* URB object
  */
-urb_t *urb_alloc(size_t data_buffer_size, size_t header_size, int num_isoc_packets);
+urb_t *urb_alloc(size_t data_buffer_size, int num_isoc_packets);
 
 /**
  * @brief Free a URB

components/usb/usb_host.c

@@ -1245,7 +1245,7 @@ exit:
 
 esp_err_t usb_host_transfer_alloc(size_t data_buffer_size, int num_isoc_packets, usb_transfer_t **transfer)
 {
-    urb_t *urb = urb_alloc(data_buffer_size, 0, num_isoc_packets);
+    urb_t *urb = urb_alloc(data_buffer_size, num_isoc_packets);
     if (urb == NULL) {
         return ESP_ERR_NO_MEM;
     }

components/usb/usb_private.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2023 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -8,17 +8,16 @@
 #include "usb_private.h"
 #include "usb/usb_types_ch9.h"
 
-urb_t *urb_alloc(size_t data_buffer_size, size_t header_size, int num_isoc_packets)
+urb_t *urb_alloc(size_t data_buffer_size, int num_isoc_packets)
 {
     urb_t *urb = heap_caps_calloc(1, sizeof(urb_t) + (sizeof(usb_isoc_packet_desc_t) * num_isoc_packets), MALLOC_CAP_DEFAULT);
-    uint8_t *data_buffer = heap_caps_malloc(data_buffer_size + header_size, MALLOC_CAP_DMA);
+    uint8_t *data_buffer = heap_caps_malloc(data_buffer_size, MALLOC_CAP_DMA);
     if (urb == NULL || data_buffer == NULL)     {
         goto err;
     }
-    urb->usb_host_header_size = header_size;    // Indicate that this URB's data_buffer has a header in front of it.
-    // Case as dummy transfer to write to initialize const fields
+    // Cast as dummy transfer so that we can assign to const fields
     usb_transfer_dummy_t *dummy_transfer = (usb_transfer_dummy_t *)&urb->transfer;
-    dummy_transfer->data_buffer = (uint8_t *)(data_buffer + header_size);
+    dummy_transfer->data_buffer = data_buffer;
     dummy_transfer->data_buffer_size = data_buffer_size;
     dummy_transfer->num_isoc_packets = num_isoc_packets;
     return urb;
@@ -33,6 +32,6 @@ void urb_free(urb_t *urb)
     if (urb == NULL) {
         return;
     }
-    heap_caps_free((uint8_t *)(urb->transfer.data_buffer - urb->usb_host_header_size));
+    heap_caps_free(urb->transfer.data_buffer);
     heap_caps_free(urb);
 }