w1: documentation update

Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 91 insertions, 38 deletions

diff --git a/Documentation/w1/w1.netlink b/Documentation/w1/w1.netlink
index 3640c7c87d45..d596d406e0a5 100644
--- a/Documentation/w1/w1.netlink
+++ b/Documentation/w1/w1.netlink
@@ -5,69 +5,122 @@ 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.
+1. Events. They are generated each time new master or slave device
+        found either due to automatic or requested search.
+2. Userspace commands.
 3. Replies to userspace commands.
 
 
 Protocol.
 ========
 
-[struct cn_msg] - connector header. It's length field is equal to size of the attached data.
+[struct cn_msg] - connector header.
+        Its 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).
+                        W1_LIST_MASTERS
+                                list current bus masters
+                        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/touch)
         __u8 res        - reserved
-        __u16 len       - size of attached to this header data.
+        __u16 len       - size of data attached to this header data
         union {
-                __u8 id;                         - slave unique device id
+                __u8 id[8];                      - slave unique device id
                 struct w1_mst {
-                        __u32           id;      - master's id.
+                        __u32           id;      - master's id
                         __u32           res;     - reserved
                 } mst;
         } id;
 
-[strucrt w1_netlink_cmd] - command for gived master or slave device.
+[struct w1_netlink_cmd] - command for given 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.
+                        W1_CMD_READ     - read command
+                        W1_CMD_WRITE    - write command
+                        W1_CMD_TOUCH    - touch command
+                                (write and sample data back to userspace)
+                        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.
+        __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.
+Each connector message can include one or more w1_netlink_msg with
+zero or 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.
+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:
 
-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;
+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;
 
+Replies to W1_LIST_MASTERS should send a message back to the userspace
+which will contain list of all registered master ids in the following
+format:
+
+        cn_msg (CN_W1_IDX.CN_W1_VAL as id, len is equal to sizeof(struct
+        w1_netlink_msg) plus number of masters multipled by 4)
+        w1_netlink_msg (type: W1_LIST_MASTERS, len is equal to
+                number of masters multiplied by 4 (u32 size))
+        id0 ... idN
+
+        Each message is at most 4k in size, so if number of master devices
+        exceeds this, it will be split into several messages,
+        cn.seq will be increased for each one.
+
+W1 search and alarm search commands.
+request:
+[cn_msg]
+  [w1_netlink_msg type = W1_MASTER_CMD
+        id is equal to the bus master id to use for searching]
+  [w1_netlink_cmd cmd = W1_CMD_SEARCH or W1_CMD_ALARM_SEARCH]
+
+reply:
+  [cn_msg, ack = 1 and increasing, 0 means the last message,
+        seq is equal to the request seq]
+  [w1_netlink_msg type = W1_MASTER_CMD]
+  [w1_netlink_cmd cmd = W1_CMD_SEARCH or W1_CMD_ALARM_SEARCH
+        len is equal to number of IDs multiplied by 8]
+  [64bit-id0 ... 64bit-idN]
+Length in each header corresponds to the size of the data behind it, so
+w1_netlink_cmd->len = N * 8; where N is number of IDs in this message.
+        Can be zero.
+w1_netlink_msg->len = sizeof(struct w1_netlink_cmd) + N * 8;
+cn_msg->len = sizeof(struct w1_netlink_msg) +
+              sizeof(struct w1_netlink_cmd) +
+              N*8;
 
 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.
+When new message (w1_netlink_msg) is received w1 core detects if it is
+master or 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.
+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.
@@ -82,8 +135,8 @@ 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 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.
@@ -93,6 +146,6 @@ 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.
+2. http://www.ioremap.net/archive/w1
+This archive includes userspace application w1d.c which uses
+read/write/search commands for all master/slave devices found on the bus.