The next API function is the AddrMulticastRemove() function used to remove an (IP-to-Ethernet) multicast hardware address from a device.
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Every device driver’s net_dev.c
Prototype
| Code Block |
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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’.
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Required Configuration
Necessary only if if NET_MCAST_CFG_IPv4_RX_EN or NET_IPMCAST_CFG_MULTICAST_SELIPv4_TX_EN is configured for transmit and receive multicasting (see NET_IP_CFG_MULTICAST_SEL).
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.Listing B-3 Example device multicast address removal
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/* ---------- 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);
} |