feat(eppp): Support for channels -- WIP

Author: david-cermak

components/eppp_link/eppp_sdio.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -8,12 +8,21 @@
 #define MAX_SDIO_PAYLOAD 1500
 #define SDIO_ALIGN(size) (((size) + 3U) & ~(3U))
 #define SDIO_PAYLOAD SDIO_ALIGN(MAX_SDIO_PAYLOAD)
+#define SDIO_PACKET_SIZE SDIO_ALIGN(MAX_SDIO_PAYLOAD + 4)
 #define PPP_SOF 0x7E
 
+#define NR_OF_CHANNELS 2
+
 // Interrupts and registers
 #define SLAVE_INTR      0
 #define SLAVE_REG_REQ   0
 
 // Requests from host to slave
 #define REQ_RESET 1
 #define REQ_INIT  2
+
+struct header {
+    uint8_t magic;
+    uint8_t channel;
+    uint16_t size;
+} __attribute__((packed));

components/eppp_link/eppp_sdio_host.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -28,8 +28,8 @@ static SemaphoreHandle_t s_essl_mutex = NULL;
 static essl_handle_t s_essl = NULL;
 static sdmmc_card_t *s_card = NULL;
 
-static DRAM_DMA_ALIGNED_ATTR uint8_t send_buffer[SDIO_PAYLOAD];
-static DMA_ATTR uint8_t rcv_buffer[SDIO_PAYLOAD];
+static DRAM_DMA_ALIGNED_ATTR uint8_t send_buffer[SDIO_PACKET_SIZE];
+static DMA_ATTR uint8_t rcv_buffer[SDIO_PACKET_SIZE];
 
 esp_err_t eppp_sdio_host_tx(void *h, void *buffer, size_t len)
 {
@@ -38,12 +38,17 @@ esp_err_t eppp_sdio_host_tx(void *h, void *buffer, size_t len)
         return ESP_OK;
     }
 
-    memcpy(send_buffer, buffer, len);
-    size_t send_len = SDIO_ALIGN(len);
-    if (send_len > len) {
-        // pad with SOF's
-        memset(&send_buffer[len], PPP_SOF, send_len - len);
-    }
+
+    struct header *head = (void *)send_buffer;
+    head->magic = PPP_SOF;
+    head->channel = 0;
+    head->size = len;
+    memcpy(send_buffer + sizeof(struct header), buffer, len);
+    size_t send_len = SDIO_ALIGN(len + sizeof(struct header));
+//    if (send_len > len) {
+//        // pad with SOF's
+//        memset(&send_buffer[len], PPP_SOF, send_len - len);
+//    }
     xSemaphoreTake(s_essl_mutex, portMAX_DELAY);
     esp_err_t ret = essl_send_packet(s_essl, send_buffer, send_len, PACKET_TIMEOUT_MS);
     if (ret != ESP_OK) {
@@ -145,15 +150,28 @@ esp_err_t eppp_sdio_host_rx(esp_netif_t *netif)
     if (intr & ESSL_SDIO_DEF_ESP32.new_packet_intr_mask) {
         esp_err_t ret;
         do {
-            size_t size_read = SDIO_PAYLOAD;
-            ret = essl_get_packet(s_essl, rcv_buffer, SDIO_PAYLOAD, &size_read, PACKET_TIMEOUT_MS);
+            size_t size_read = SDIO_PACKET_SIZE;
+            ret = essl_get_packet(s_essl, rcv_buffer, SDIO_PACKET_SIZE, &size_read, PACKET_TIMEOUT_MS);
             if (ret == ESP_ERR_NOT_FOUND) {
                 ESP_LOGE(TAG, "interrupt but no data can be read");
                 break;
             } else if (ret == ESP_OK) {
                 ESP_LOGD(TAG, "receive data, size: %d", size_read);
+                struct header *head = (void *)rcv_buffer;
+                if (head->magic != PPP_SOF) {
+                    ESP_LOGE(TAG, "invalid magic %x", head->magic);
+                    break;
+                }
+                if (head->channel >= NR_OF_CHANNELS) {
+                    ESP_LOGE(TAG, "invalid channel %x", head->channel);
+                    break;
+                }
+                if (head->size > SDIO_PAYLOAD || head->size > size_read) {
+                    ESP_LOGE(TAG, "invalid size %x", head->size);
+                    break;
+                }
                 ESP_LOG_BUFFER_HEXDUMP(TAG, rcv_buffer, size_read, ESP_LOG_VERBOSE);
-                esp_netif_receive(netif, rcv_buffer, size_read, NULL);
+                esp_netif_receive(netif, rcv_buffer + sizeof(struct header), head->size, NULL);
                 break;
             } else {
                 ESP_LOGE(TAG, "rx packet error: %08X", ret);

components/eppp_link/eppp_sdio_slave.c

@@ -27,12 +27,16 @@ esp_err_t eppp_sdio_slave_tx(void *h, void *buffer, size_t len)
         // silently skip the Tx if the SDIO not fully initialized
         return ESP_OK;
     }
-    memcpy(sdio_slave_tx_buffer, buffer, len);
-    size_t send_len = SDIO_ALIGN(len);
-    if (send_len > len) {
-        // pad with SOF's if the size is not 4 bytes aligned
-        memset(&sdio_slave_tx_buffer[len], PPP_SOF, send_len - len);
-    }
+    struct header *head = (void *)sdio_slave_tx_buffer;
+    head->magic = PPP_SOF;
+    head->channel = 0;
+    head->size = len;
+    memcpy(sdio_slave_tx_buffer + sizeof(struct header), buffer, len);
+    size_t send_len = SDIO_ALIGN(len + sizeof(struct header));
+//    if (send_len > len) {
+//        // pad with SOF's if the size is not 4 bytes aligned
+//        memset(&sdio_slave_tx_buffer[len], PPP_SOF, send_len - len);
+//    }
 
     ESP_LOG_BUFFER_HEXDUMP(TAG, sdio_slave_tx_buffer, send_len, ESP_LOG_VERBOSE);
     esp_err_t ret = sdio_slave_transmit(sdio_slave_tx_buffer, send_len);
@@ -82,7 +86,21 @@ esp_err_t eppp_sdio_slave_rx(esp_netif_t *netif)
     if (ret == ESP_ERR_NOT_FINISHED || ret == ESP_OK) {
 again:
         ptr = sdio_slave_recv_get_buf(handle, &length);
-        esp_netif_receive(netif, ptr, length, NULL);
+        struct header *head = (void *)ptr;
+        if (head->magic != PPP_SOF) {
+            ESP_LOGE(TAG, "invalid magic %x", head->magic);
+            return ESP_FAIL;
+        }
+        if (head->channel >= NR_OF_CHANNELS) {
+            ESP_LOGE(TAG, "invalid channel %x", head->channel);
+            return ESP_FAIL;
+        }
+        if (head->size > SDIO_PAYLOAD || head->size > length) {
+            ESP_LOGE(TAG, "invalid size %x", head->size);
+            return ESP_FAIL;
+        }
+
+        esp_netif_receive(netif, ptr + sizeof(struct header), head->size, NULL);
         if (sdio_slave_recv_load_buf(handle) != ESP_OK) {
             ESP_LOGE(TAG, "Failed to recycle packet buffer");
             return ESP_FAIL;