Am 01.02.2011 17:33, schrieb Kurt Van Dijck:
diff --git a/include/linux/can.h b/include/linux/can.h
+/* particular protocols of the protocol family PF_CAN */
+#define CAN_RAW 1 /* RAW sockets */
+#define CAN_BCM 2 /* Broadcast Manager */
+#define CAN_TP16 3 /* VAG Transport Protocol v1.6 */
+#define CAN_TP20 4 /* VAG Transport Protocol v2.0 */
+#define CAN_MCNET 5 /* Bosch MCNet */
+#define CAN_ISOTP 6 /* ISO 15765-2 Transport Protocol */
+#define CAN_J1939 7 /* SAE J1939 */
Very nice :-)
+#define CAN_NPROTO 8
+
+#define SOL_CAN_BASE 100
+
+/**
+ * struct sockaddr_can - the sockaddr structure for CAN sockets
+ * @can_family: address family number AF_CAN.
+ * @can_ifindex: CAN network interface index.
+ * @can_addr: protocol specific address information
+ */
+struct sockaddr_can {
+ sa_family_t can_family;
+ int can_ifindex;
+ union {
+ /* transport protocol class address information (e.g. ISOTP) */
+ struct { canid_t rx_id, tx_id; } tp;
+
+ /* J1939 address information */
+ struct {
+ /* 8 byte name when using dynamic addressing */
+ __u64 name;
+ /*
+ * pgn:
+ * 8bit: PS in PDU2 case, else 0
+ * 8bit: PF
+ * 1bit: DP
+ * 1bit: reserved
+ */
+ __u32 pgn;
+
+ /* 1byte address */
+ __u8 addr;
+ } j1939;
+
+ /* reserved for future CAN protocols address information */
+ } can_addr;
+};
struct sockaddr is 16 Bytes long and is defined here:
http://lxr.linux.no/#linux+v2.6.37/include/linux/socket.h#L42
struct sockaddr_in is defined here:
http://lxr.linux.no/#linux+v2.6.37/include/linux/in.h#L181
And as you can see, the inet-guys managed to extend their struct to the
maximum size of 16 bytes total with the __pad[] array.
I did not see this idea before, so the struct sockaddr_can is:
http://lxr.linux.no/#linux+v2.6.37/include/linux/can.h#L73
struct sockaddr_can {
sa_family_t can_family;
int can_ifindex;
union {
/* transport protocol class address info (e.g. ISOTP) */
struct { canid_t rx_id, tx_id; } tp;
/* reserved for future CAN protocols address information */
} can_addr;
};
This struct sockaddr_can has a length of 2+4+4+4 = 14 bytes which fit's
fortunately into the max 16 bytes specified by struct sockaddr.
Your proposed structure is
2+4+8+4+1 = 19
Unfortunately this does not fit.
Also the problem can not be solved to make struct sockaddr_can longer
than 14 bytes. E.g. if you build a CAN application with the new
sockaddr_can and then try to run this binary (16 byte struct) on an
older kernel expecting a 14 bytes (max 16 bytes) struct. :-(
So it is assumed that the address information for j1939 is limited to
the 8 bytes in the can_addr union that has been reserved by struct tp.
What about ...
struct sockaddr_can {
sa_family_t can_family;
int can_ifindex;
union {
/* transport protocol class address info (e.g. ISOTP) */
struct { canid_t rx_id, tx_id; } tp;
struct {
/* parameter group number */
struct {
__u8 ps;
__u8 pf;
__u8 dp:1,
res:1;
} pgn;
/* 1byte address */
__u8 addr;
} j1939;
/* reserved for future CAN protocols address information */
} can_addr;
};
and putting the
"/* 8 byte name when using dynamic addressing */"
into a sockopt?
So far you defined:
+#define J1939_NO_NAME 0
which says to me that it can be '0' or a valid 'name'.
Therefore this 'name' could be set by an socket option too, simply:
When it is set with a non-zero value before a bind()-syscall, the
dynamic addressing is used.
+/*
+ * J1939 NAME
+ *
+ * bit 0-20 : Identity Number
+ * bit 21-31 : Manufacturer Code
+ * bit 32-34 : ECU Instance
+ * bit 35-39 : Function Instance
+ * bit 40-47 : Function
+ * bit 48 : Reserved
+ * bit 49-55 : Vehicle System
+ * bit 56-59 : Vehicle System Instance
+ * bit 60-62 : Industry Group
+ * bit 63 : Arbitrary Address Capable
+ */
+typedef __u64 name_t;
Expect these kind of typedefs to be remarked as unwanted on the
netdev-ML. Typedefs may 'hide' things and therefore there are not
wanted. I had a longer discussion on this for the canid_t ...
Btw. how dou you ensure the endian problem to be solved, when working
with __u64 bitfields?
Regards,
Oliver
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