Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 1 | Userspace communication protocol over connector [1]. |
| 2 | |
| 3 | |
| 4 | Message types. |
| 5 | ============= |
| 6 | |
| 7 | There are three types of messages between w1 core and userspace: |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 8 | 1. Events. They are generated each time new master or slave device |
| 9 | found either due to automatic or requested search. |
| 10 | 2. Userspace commands. |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 11 | 3. Replies to userspace commands. |
| 12 | |
| 13 | |
| 14 | Protocol. |
| 15 | ======== |
| 16 | |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 17 | [struct cn_msg] - connector header. |
| 18 | Its length field is equal to size of the attached data |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 19 | [struct w1_netlink_msg] - w1 netlink header. |
| 20 | __u8 type - message type. |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 21 | W1_LIST_MASTERS |
| 22 | list current bus masters |
| 23 | W1_SLAVE_ADD/W1_SLAVE_REMOVE |
| 24 | slave add/remove events |
| 25 | W1_MASTER_ADD/W1_MASTER_REMOVE |
| 26 | master add/remove events |
| 27 | W1_MASTER_CMD |
| 28 | userspace command for bus master |
| 29 | device (search/alarm search) |
| 30 | W1_SLAVE_CMD |
| 31 | userspace command for slave device |
| 32 | (read/write/touch) |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 33 | __u8 res - reserved |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 34 | __u16 len - size of data attached to this header data |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 35 | union { |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 36 | __u8 id[8]; - slave unique device id |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 37 | struct w1_mst { |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 38 | __u32 id; - master's id |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 39 | __u32 res; - reserved |
| 40 | } mst; |
| 41 | } id; |
| 42 | |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 43 | [struct w1_netlink_cmd] - command for given master or slave device. |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 44 | __u8 cmd - command opcode. |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 45 | W1_CMD_READ - read command |
| 46 | W1_CMD_WRITE - write command |
| 47 | W1_CMD_TOUCH - touch command |
| 48 | (write and sample data back to userspace) |
| 49 | W1_CMD_SEARCH - search command |
| 50 | W1_CMD_ALARM_SEARCH - alarm search command |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 51 | __u8 res - reserved |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 52 | __u16 len - length of data for this command |
| 53 | For read command data must be allocated like for write command |
| 54 | __u8 data[0] - data for this command |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 55 | |
| 56 | |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 57 | Each connector message can include one or more w1_netlink_msg with |
| 58 | zero or more attached w1_netlink_cmd messages. |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 59 | |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 60 | For event messages there are no w1_netlink_cmd embedded structures, |
| 61 | only connector header and w1_netlink_msg strucutre with "len" field |
| 62 | being zero and filled type (one of event types) and id: |
| 63 | either 8 bytes of slave unique id in host order, |
| 64 | or master's id, which is assigned to bus master device |
| 65 | when it is added to w1 core. |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 66 | |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 67 | Currently replies to userspace commands are only generated for read |
| 68 | command request. One reply is generated exactly for one w1_netlink_cmd |
| 69 | read request. Replies are not combined when sent - i.e. typical reply |
| 70 | messages looks like the following: |
| 71 | |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 72 | [cn_msg][w1_netlink_msg][w1_netlink_cmd] |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 73 | cn_msg.len = sizeof(struct w1_netlink_msg) + |
| 74 | sizeof(struct w1_netlink_cmd) + |
| 75 | cmd->len; |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 76 | w1_netlink_msg.len = sizeof(struct w1_netlink_cmd) + cmd->len; |
| 77 | w1_netlink_cmd.len = cmd->len; |
| 78 | |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 79 | Replies to W1_LIST_MASTERS should send a message back to the userspace |
| 80 | which will contain list of all registered master ids in the following |
| 81 | format: |
| 82 | |
| 83 | cn_msg (CN_W1_IDX.CN_W1_VAL as id, len is equal to sizeof(struct |
| 84 | w1_netlink_msg) plus number of masters multipled by 4) |
| 85 | w1_netlink_msg (type: W1_LIST_MASTERS, len is equal to |
| 86 | number of masters multiplied by 4 (u32 size)) |
| 87 | id0 ... idN |
| 88 | |
| 89 | Each message is at most 4k in size, so if number of master devices |
| 90 | exceeds this, it will be split into several messages, |
| 91 | cn.seq will be increased for each one. |
| 92 | |
| 93 | W1 search and alarm search commands. |
| 94 | request: |
| 95 | [cn_msg] |
| 96 | [w1_netlink_msg type = W1_MASTER_CMD |
| 97 | id is equal to the bus master id to use for searching] |
| 98 | [w1_netlink_cmd cmd = W1_CMD_SEARCH or W1_CMD_ALARM_SEARCH] |
| 99 | |
| 100 | reply: |
| 101 | [cn_msg, ack = 1 and increasing, 0 means the last message, |
| 102 | seq is equal to the request seq] |
| 103 | [w1_netlink_msg type = W1_MASTER_CMD] |
| 104 | [w1_netlink_cmd cmd = W1_CMD_SEARCH or W1_CMD_ALARM_SEARCH |
| 105 | len is equal to number of IDs multiplied by 8] |
| 106 | [64bit-id0 ... 64bit-idN] |
| 107 | Length in each header corresponds to the size of the data behind it, so |
| 108 | w1_netlink_cmd->len = N * 8; where N is number of IDs in this message. |
| 109 | Can be zero. |
| 110 | w1_netlink_msg->len = sizeof(struct w1_netlink_cmd) + N * 8; |
| 111 | cn_msg->len = sizeof(struct w1_netlink_msg) + |
| 112 | sizeof(struct w1_netlink_cmd) + |
| 113 | N*8; |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 114 | |
| 115 | Operation steps in w1 core when new command is received. |
| 116 | ======================================================= |
| 117 | |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 118 | When new message (w1_netlink_msg) is received w1 core detects if it is |
| 119 | master or slave request, according to w1_netlink_msg.type field. |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 120 | Then master or slave device is searched for. |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 121 | When found, master device (requested or those one on where slave device |
| 122 | is found) is locked. If slave command is requested, then reset/select |
| 123 | procedure is started to select given device. |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 124 | |
| 125 | Then all requested in w1_netlink_msg operations are performed one by one. |
| 126 | If command requires reply (like read command) it is sent on command completion. |
| 127 | |
| 128 | When all commands (w1_netlink_cmd) are processed muster device is unlocked |
| 129 | and next w1_netlink_msg header processing started. |
| 130 | |
| 131 | |
| 132 | Connector [1] specific documentation. |
| 133 | ==================================== |
| 134 | |
| 135 | Each connector message includes two u32 fields as "address". |
| 136 | w1 uses CN_W1_IDX and CN_W1_VAL defined in include/linux/connector.h header. |
| 137 | Each message also includes sequence and acknowledge numbers. |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 138 | Sequence number for event messages is appropriate bus master sequence number |
| 139 | increased with each event message sent "through" this master. |
Evgeniy Polyakov | 1200337 | 2006-03-23 19:11:58 +0300 | [diff] [blame] | 140 | Sequence number for userspace requests is set by userspace application. |
| 141 | Sequence number for reply is the same as was in request, and |
| 142 | acknowledge number is set to seq+1. |
| 143 | |
| 144 | |
| 145 | Additional documantion, source code examples. |
| 146 | ============================================ |
| 147 | |
| 148 | 1. Documentation/connector |
Evgeniy Polyakov | e4e056a | 2009-01-07 18:09:02 -0800 | [diff] [blame] | 149 | 2. http://www.ioremap.net/archive/w1 |
| 150 | This archive includes userspace application w1d.c which uses |
| 151 | read/write/search commands for all master/slave devices found on the bus. |