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Diffstat (limited to 'Documentation/w1')
| -rw-r--r-- | Documentation/w1/w1.netlink | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/Documentation/w1/w1.netlink b/Documentation/w1/w1.netlink new file mode 100644 index 000000000000..3640c7c87d45 --- /dev/null +++ b/Documentation/w1/w1.netlink @@ -0,0 +1,98 @@ +Userspace communication protocol over connector [1]. + + +Message types. +============= + +There are three types of messages between w1 core and userspace: +1. Events. They are generated each time new master or slave device found + either due to automatic or requested search. +2. Userspace commands. Includes read/write and search/alarm search comamnds. +3. Replies to userspace commands. + + +Protocol. +======== + +[struct cn_msg] - connector header. It's length field is equal to size of the attached data. +[struct w1_netlink_msg] - w1 netlink header. + __u8 type - message type. + W1_SLAVE_ADD/W1_SLAVE_REMOVE - slave add/remove events. + W1_MASTER_ADD/W1_MASTER_REMOVE - master add/remove events. + W1_MASTER_CMD - userspace command for bus master device (search/alarm search). + W1_SLAVE_CMD - userspace command for slave device (read/write/ search/alarm search + for bus master device where given slave device found). + __u8 res - reserved + __u16 len - size of attached to this header data. + union { + __u8 id; - slave unique device id + struct w1_mst { + __u32 id; - master's id. + __u32 res; - reserved + } mst; + } id; + +[strucrt w1_netlink_cmd] - command for gived master or slave device. + __u8 cmd - command opcode. + W1_CMD_READ - read command. + W1_CMD_WRITE - write command. + W1_CMD_SEARCH - search command. + W1_CMD_ALARM_SEARCH - alarm search command. + __u8 res - reserved + __u16 len - length of data for this command. + For read command data must be allocated like for write command. + __u8 data[0] - data for this command. + + +Each connector message can include one or more w1_netlink_msg with zero of more attached w1_netlink_cmd messages. + +For event messages there are no w1_netlink_cmd embedded structures, only connector header +and w1_netlink_msg strucutre with "len" field being zero and filled type (one of event types) +and id - either 8 bytes of slave unique id in host order, or master's id, which is assigned +to bus master device when it is added to w1 core. + +Currently replies to userspace commands are only generated for read command request. +One reply is generated exactly for one w1_netlink_cmd read request. +Replies are not combined when sent - i.e. typical reply messages looks like the following: +[cn_msg][w1_netlink_msg][w1_netlink_cmd] +cn_msg.len = sizeof(struct w1_netlink_msg) + sizeof(struct w1_netlink_cmd) + cmd->len; +w1_netlink_msg.len = sizeof(struct w1_netlink_cmd) + cmd->len; +w1_netlink_cmd.len = cmd->len; + + +Operation steps in w1 core when new command is received. +======================================================= + +When new message (w1_netlink_msg) is received w1 core detects if it is master of slave request, +according to w1_netlink_msg.type field. +Then master or slave device is searched for. +When found, master device (requested or those one on where slave device is found) is locked. +If slave command is requested, then reset/select procedure is started to select given device. + +Then all requested in w1_netlink_msg operations are performed one by one. +If command requires reply (like read command) it is sent on command completion. + +When all commands (w1_netlink_cmd) are processed muster device is unlocked +and next w1_netlink_msg header processing started. + + +Connector [1] specific documentation. +==================================== + +Each connector message includes two u32 fields as "address". +w1 uses CN_W1_IDX and CN_W1_VAL defined in include/linux/connector.h header. +Each message also includes sequence and acknowledge numbers. +Sequence number for event messages is appropriate bus master sequence number increased with +each event message sent "through" this master. +Sequence number for userspace requests is set by userspace application. +Sequence number for reply is the same as was in request, and +acknowledge number is set to seq+1. + + +Additional documantion, source code examples. +============================================ + +1. Documentation/connector +2. http://tservice.net.ru/~s0mbre/archive/w1 +This archive includes userspace application w1d.c which +uses read/write/search commands for all master/slave devices found on the bus. |