Documentation/w1/w1-netlink.rst

Source file repositories/reference/linux-study-clean/Documentation/w1/w1-netlink.rst

File Facts

System
Linux kernel
Corpus path
Documentation/w1/w1-netlink.rst
Extension
.rst
Size
7260 bytes
Lines
203
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

struct w1_mst {
			__u32		id;	 - master's id
			__u32		res;	 - reserved
		} mst;
	} id;

  [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_TOUCH	- touch command
				(write and sample data back to userspace)
			W1_CMD_RESET	- send bus reset
			W1_CMD_SLAVE_ADD	- add slave to kernel list
			W1_CMD_SLAVE_REMOVE	- remove slave from kernel list
			W1_CMD_LIST_SLAVES	- get slaves list from kernel
	__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 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 structure 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;

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 multiplied 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.

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::

Annotation

Implementation Notes