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-rw-r--r--Documentation/networking/can.txt20
1 files changed, 18 insertions, 2 deletions
diff --git a/Documentation/networking/can.txt b/Documentation/networking/can.txt
index 0a2859a8ee7e..5abad1e921ca 100644
--- a/Documentation/networking/can.txt
+++ b/Documentation/networking/can.txt
@@ -22,7 +22,8 @@ This file contains
4.1.3 RAW socket option CAN_RAW_LOOPBACK
4.1.4 RAW socket option CAN_RAW_RECV_OWN_MSGS
4.1.5 RAW socket option CAN_RAW_FD_FRAMES
- 4.1.6 RAW socket returned message flags
+ 4.1.6 RAW socket option CAN_RAW_JOIN_FILTERS
+ 4.1.7 RAW socket returned message flags
4.2 Broadcast Manager protocol sockets (SOCK_DGRAM)
4.2.1 Broadcast Manager operations
4.2.2 Broadcast Manager message flags
@@ -601,7 +602,22 @@ solution for a couple of reasons:
CAN FD frames by checking if the device maximum transfer unit is CANFD_MTU.
The CAN device MTU can be retrieved e.g. with a SIOCGIFMTU ioctl() syscall.
- 4.1.6 RAW socket returned message flags
+ 4.1.6 RAW socket option CAN_RAW_JOIN_FILTERS
+
+ The CAN_RAW socket can set multiple CAN identifier specific filters that
+ lead to multiple filters in the af_can.c filter processing. These filters
+ are indenpendent from each other which leads to logical OR'ed filters when
+ applied (see 4.1.1).
+
+ This socket option joines the given CAN filters in the way that only CAN
+ frames are passed to user space that matched *all* given CAN filters. The
+ semantic for the applied filters is therefore changed to a logical AND.
+
+ This is useful especially when the filterset is a combination of filters
+ where the CAN_INV_FILTER flag is set in order to notch single CAN IDs or
+ CAN ID ranges from the incoming traffic.
+
+ 4.1.7 RAW socket returned message flags
When using recvmsg() call, the msg->msg_flags may contain following flags: