NetDev_AddrMulticastRemove() (Ethernet)

The next API function is the AddrMulticastRemove() function used to remove an (IP-to-Ethernet) multicast hardware address from a device.

Files

Every device driver’s net_dev.c

Prototype

          static void NetDev_AddrMulticastRemove (NET_IF     *p_if,
                                                  CPU_INT08U *p_addr_hw,
                                                  CPU_INT08U  addr_hw_len,
                                                  NET_ERR    *p_err);

Note that since every device driver’s AddrMulticastRemove() function is accessed only by function pointer via the device driver’s API structure, it doesn’t need to be globally available and should therefore be declared as ‘static’.

Arguments

p_if

Pointer to the interface to remove a multicast address.

p_addr_hw

Pointer to multicast hardware address to remove.

addr_hw_len

Length of multicast hardware address.

p_err

Pointer to variable that will receive the return error code from this function.

Returned Value

None.

Required Configuration

Necessary only if NET_MCAST_CFG_IPv4_RX_EN or NET_MCAST_CFG_IPv4_TX_EN is configured for transmit and receive multicasting.

Notes / Warnings

Use same exact code as in NetDev_AddrMulticastAdd() to calculate the device’s CRC hash (see NetDev_MgmtDemux()), but remove a multicast address by decrementing the device’s hash bit reference counters and clearing the appropriate bits in the device’s multicast registers.

                                                            /* ---------- CALCULATE HASH CODE ---------- */
          /* Use NetDev_AddrMulticastAdd()'s algorithm to calculate CRC hash.                            */
                                                            /* - REMOVE MULTICAST ADDRESS FROM DEVICE -- */
          paddr_hash_ctrs = &pdev_data->MulticastAddrHashBitCtr[hash];
          if (*paddr_hash_ctrs > 1u) {                      /* If multiple multicast addresses hashed, ..*/
             (*paddr_hash_ctrs)--;                          /* .. decrement hash bit reference counter ..*/
              *perr = NET_DEV_ERR_NONE;                     /* .. but do NOT unconfigure hash register.  */
               return;
          }
          *paddr_hash_ctrs = 0u;                            /* Clear hash bit reference counter.         */
           
          if (hash <= 31u) {                                /* Clear multicast hash register bit.        */
              pdev->MCAST_REG_LO &= ~(1u << reg_bit);       /* (Substitute 'MCAST_REG_LO/HI' with ..     */
          } else {                                          /* .. device's actual multicast registers.)  */
              pdev->MCAST_REG_HI &= ~(1u << reg_bit);
          }