Zero-copy for STM32 MAC driver.

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@4985 35acf78f-673a-0410-8e92-d51de3d6d3f4

os/hal/platforms/AT91SAM7/mac_lld.h

@@ -35,6 +35,11 @@
 /* Driver constants.                                                         */
 /*===========================================================================*/
 
+/**
+ * @brief   This implementation does not support the zero-copy mode API.
+ */
+#define MAC_SUPPORTS_ZERO_COPY      FALSE
+
 #define EMAC_RECEIVE_BUFFERS_SIZE       128     /* Do not modify */
 #define EMAC_TRANSMIT_BUFFERS_SIZE      MAC_BUFFERS_SIZE
 #define EMAC_RECEIVE_DESCRIPTORS                                            \

os/hal/platforms/STM32/mac_lld.c

@@ -624,18 +624,26 @@ bool_t mac_lld_poll_link_status(MACDriver *macp) {
  *                      on the first call then scale the value down subtracting
  *                      the amount of data already copied into the previous
  *                      buffers.
- * @param[out] sizep    pointer to variable receiving the real buffer size.
- *                      The returned value can be less than the amount
- *                      requested, this means that more buffers must be
- *                      requested in order to fill the frame data entirely.
+ * @param[out] sizep    pointer to variable receiving the buffer size, it is
+ *                      zero when the last buffer has already been returned.
+ *                      Note that a returned size lower than the amount
+ *                      requested means that more buffers must be requested
+ *                      in order to fill the frame data entirely.
  * @return              Pointer to the returned buffer.
+ * @retval NULL         if the buffer chain has been entirely scanned.
  *
  * @notapi
  */
 uint8_t *mac_lld_get_next_transmit_buffer(MACTransmitDescriptor *tdp,
                                           size_t size,
                                           size_t *sizep) {
-  (void)tdp; (void)size; (void)sizep;
+
+  if (tdp->offset == 0) {
+    *sizep      = tdp->size;
+    tdp->offset = size;
+    return (uint8_t *)tdp->physdesc->tdes2;
+  }
+  *sizep = 0;
   return NULL;
 }
 
@@ -655,7 +663,14 @@ uint8_t *mac_lld_get_next_transmit_buffer(MACTransmitDescriptor *tdp,
  */
 const uint8_t *mac_lld_get_next_receive_buffer(MACReceiveDescriptor *rdp,
                                                size_t *sizep) {
-  (void)rdp; (void)sizep;
+
+  if (rdp->size > 0) {
+    *sizep      = rdp->size;
+    rdp->offset = rdp->size;
+    rdp->size   = 0;
+    return (uint8_t *)rdp->physdesc->rdes2;
+  }
+  *sizep = 0;
   return NULL;
 }
 #endif /* MAC_USE_ZERO_COPY */

os/hal/platforms/STM32/mac_lld.h

@@ -291,7 +291,6 @@ typedef struct {
    * @brief Available space size.
    */
   size_t                    size;
-  /* End of the mandatory fields.*/
   /**
    * @brief Pointer to the physical descriptor.
    */
@@ -310,7 +309,6 @@ typedef struct {
    * @brief Available data size.
    */
   size_t                size;
-  /* End of the mandatory fields.*/
   /**
    * @brief Pointer to the physical descriptor.
    */

readme.txt

@@ -90,6 +90,8 @@
   (backported to 2.4.3).
 - FIX: Fixed wrong SPI path in platform_f105_f107.mk (bug 3598151).
 - FIX: Fixed PHY powerdown issues not fixed (bug 3596911).
+- NEW: Added zero-copy capability to the STM32 MAC driver (experimental and
+  not tested yet).
 - NEW: Added an optional zero-copy mode API to the MAC driver model.
 - NEW: Added EXT driver to the STM32F3xx platform.
 - NEW: Improved the STM32 EXT driver to support more than 32 channels.