Merge remote-tracking branches 'asoc/fix/adsp', 'asoc/fix/arizona', 'asoc/fix/atmel...

[linux-drm-fsl-dcu.git] / Documentation / networking / packet_mmap.txt

diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt
index c01223628a87ae5e522b714c8a3a86edda15dea5..8e48e3b142275ff1500df754301d39c7f1639d71 100644 (file)
--- a/Documentation/networking/packet_mmap.txt
+++ b/Documentation/networking/packet_mmap.txt
@@ -123,6 +123,16 @@ Transmission process is similar to capture as shown below.
 [shutdown]  close() --------> destruction of the transmission socket and
                               deallocation of all associated resources.
 
+Socket creation and destruction is also straight forward, and is done
+the same way as in capturing described in the previous paragraph:
+
+ int fd = socket(PF_PACKET, mode, 0);
+
+The protocol can optionally be 0 in case we only want to transmit
+via this socket, which avoids an expensive call to packet_rcv().
+In this case, you also need to bind(2) the TX_RING with sll_protocol = 0
+set. Otherwise, htons(ETH_P_ALL) or any other protocol, for example.
+
 Binding the socket to your network interface is mandatory (with zero copy) to
 know the header size of frames used in the circular buffer.