99 lines
4.0 KiB
Plaintext
99 lines
4.0 KiB
Plaintext
|
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.
|