W1: Dallas’ 1-wire bus¶
W1 API internal to the kernel¶
W1 API internal to the kernel¶
include/linux/w1.h¶
W1 kernel API functions.
broken out slave device id
Definition
Members
family identifies the type of device id along with family is the unique device id crc checksum of the other bytes crc checksum of the other bytes id along with family is the unique device id family identifies the type of device struct w1_slave В¶
holds a single slave device on the bus
Definition
Members
owner Points to the one wire “wire” kernel module. name Device id is ascii. w1_slave_entry data for the linked list reg_num the slave id in binary refcnt reference count, delete when 0 ttl decrement per search this slave isn’t found, deatch at 0 flags bit flags for W1_SLAVE_ACTIVE W1_SLAVE_DETACH master bus which this slave is on family module for device family type family_data pointer for use by the family module dev kernel device identifier hwmon pointer to hwmon device struct w1_bus_master ¶
operations available on a bus master
Definition
Members
data the first parameter in all the functions below read_bit Sample the line level return the level read (0 or 1) write_bit Sets the line level touch_bit the lowest-level function for devices that really support the 1-wire protocol. touch_bit(0) = write-0 cycle touch_bit(1) = write-1 / read cycle return the bit read (0 or 1) read_byte Reads a bytes. Same as 8 touch_bit(1) calls. return the byte read write_byte Writes a byte. Same as 8 touch_bit(x) calls. read_block Same as a series of read_byte() calls return the number of bytes read write_block Same as a series of write_byte() calls triplet Combines two reads and a smart write for ROM searches return bit0=Id bit1=comp_id bit2=dir_taken reset_bus long write-0 with a read for the presence pulse detection return -1=Error, 0=Device present, 1=No device present set_pullup Put out a strong pull-up pulse of the specified duration. return -1=Error, 0=completed search Really nice hardware can handles the different types of ROM search w1_master* is passed to the slave found callback. u8 is search_type, W1_SEARCH or W1_ALARM_SEARCH dev_id Optional device id string, which w1 slaves could use for creating names, which then give a connection to the w1 master
Note
read_bit and write_bit are very low level functions and should only be used with hardware that doesn’t really support 1-wire operations, like a parallel/serial port. Either define read_bit and write_bit OR define, at minimum, touch_bit and reset_bus.
bitfields used in w1_master.flags
Constants
W1_ABORT_SEARCH abort searching early on shutdown W1_WARN_MAX_COUNT limit warning when the maximum count is reached struct w1_master В¶
one per bus master
Definition
Members
w1_master_entry master linked list owner module owner name dynamically allocate bus name list_mutex protect slist and async_list slist linked list of slaves async_list linked list of netlink commands to execute max_slave_count maximum number of slaves to search for at a time slave_count current number of slaves known attempts number of searches ran slave_ttl number of searches before a slave is timed out initialized prevent init/removal race conditions id w1 bus number search_count number of automatic searches to run, -1 unlimited search_id allows continuing a search refcnt reference count priv private data storage enable_pullup allows a strong pullup pullup_duration time for the next strong pullup flags one of w1_master_flags thread thread for bus search and netlink commands mutex protect most of w1_master bus_mutex pretect concurrent bus access driver sysfs driver dev sysfs device bus_master io operations available seq sequence number used for netlink broadcasts struct w1_family_ops В¶
operations for a family type
Definition
Members
add_slave add_slave remove_slave remove_slave groups sysfs group chip_info pointer to struct hwmon_chip_info struct w1_family В¶
reference counted family structure.
Definition
Members
family_entry family linked list fid 8 bit family identifier fops operations for this family refcnt reference counter module_w1_family ( __w1_family ) В¶
Helper macro for registering a 1-Wire families
Parameters
__w1_family w1_family struct
Description
Helper macro for 1-Wire families which do not do anything special in module init/exit. This eliminates a lot of boilerplate. Each module may only use this macro once, and calling it replaces module_init() and module_exit()
drivers/w1/w1.c¶
W1 core functions.
void w1_search ( struct w1_master * dev, u8 search_type, w1_slave_found_callback cb ) В¶
Performs a ROM Search & registers any devices found.
Parameters
struct w1_master * dev The master device to search u8 search_type W1_SEARCH to search all devices, or W1_ALARM_SEARCH to return only devices in the alarmed state w1_slave_found_callback cb Function to call when a device is found
Description
The 1-wire search is a simple binary tree search. For each bit of the address, we read two bits and write one bit. The bit written will put to sleep all devies that don’t match that bit. When the two reads differ, the direction choice is obvious. When both bits are 0, we must choose a path to take. When we can scan all 64 bits without having to choose a path, we are done.
See “Application note 187 1-wire search algorithm” at www.maxim-ic.com
int w1_process_callbacks ( struct w1_master * dev ) В¶
execute each dev->async_list callback entry
Parameters
struct w1_master * dev w1_master device
Description
The w1 master list_mutex must be held.
Return
1 if there were commands to executed 0 otherwise
drivers/w1/w1_family.c¶
Allows registering device family operations.
int w1_register_family ( struct w1_family * newf ) В¶
register a device family driver
Parameters
struct w1_family * newf family to register void w1_unregister_family ( struct w1_family * fent ) В¶
unregister a device family driver
Parameters
struct w1_family * fent family to unregister
drivers/w1/w1_internal.h¶
W1 internal initialization for master devices.
execute callback from the w1_process kthread
Definition
Members
async_entry link entry cb callback function, must list_del and destroy this list before returning
Description
When inserted into the w1_master async_list, w1_process will execute the callback. Embed this into the structure with the command details.
drivers/w1/w1_int.c¶
W1 internal initialization for master devices.
int w1_add_master_device ( struct w1_bus_master * master ) В¶
registers a new master device
Parameters
struct w1_bus_master * master master bus device to register void w1_remove_master_device ( struct w1_bus_master * bm ) В¶
unregister a master device
Parameters
struct w1_bus_master * bm master bus device to remove
drivers/w1/w1_netlink.h¶
W1 external netlink API structures and commands.
bitfield flags for struct cn_msg.flags
Constants
W1_CN_BUNDLE Request bundling replies into fewer messagse. Be prepared to handle multiple struct cn_msg, struct w1_netlink_msg, and struct w1_netlink_cmd in one packet. enum w1_netlink_message_types В¶
Constants
W1_SLAVE_ADD notification that a slave device was added W1_SLAVE_REMOVE notification that a slave device was removed W1_MASTER_ADD notification that a new bus master was added W1_MASTER_REMOVE notification that a bus masterwas removed W1_MASTER_CMD initiate operations on a specific master W1_SLAVE_CMD sends reset, selects the slave, then does a read/write/touch operation W1_LIST_MASTERS used to determine the bus master identifiers struct w1_netlink_msg В¶
holds w1 message type, id, and result
Definition
Members
type one of enum w1_netlink_message_types status kernel feedback for success 0 or errno failure value len length of data following w1_netlink_msg id union holding bus master id (msg.id) and slave device id (id[8]). id.id Slave ID (8 bytes) id.mst bus master identification id.mst.id bus master ID id.mst.res bus master reserved data start address of any following data
Description
The base message structure for w1 messages over netlink. The netlink connector data sequence is, struct nlmsghdr, struct cn_msg, then one or more struct w1_netlink_msg (each with optional data).
commands available for master or slave operations
Constants
W1_CMD_READ read len bytes W1_CMD_WRITE write len bytes W1_CMD_SEARCH initiate a standard search, returns only the slave devices found during that search W1_CMD_ALARM_SEARCH search for devices that are currently alarming W1_CMD_TOUCH Touches a series of bytes. W1_CMD_RESET sends a bus reset on the given master W1_CMD_SLAVE_ADD adds a slave to the given master, 8 byte slave id at data[0] W1_CMD_SLAVE_REMOVE removes a slave to the given master, 8 byte slave id at data[0] W1_CMD_LIST_SLAVES list of slaves registered on this master W1_CMD_MAX number of available commands struct w1_netlink_cmd В¶
holds the command and data
Definition
Members
cmd one of enum w1_commands res reserved len length of data following w1_netlink_cmd data start address of any following data
Description
One or more struct w1_netlink_cmd is placed starting at w1_netlink_msg.data each with optional data.
drivers/w1/w1_io.c¶
u8 w1_touch_bit ( struct w1_master * dev, int bit ) В¶
Generates a write-0 or write-1 cycle and samples the level.
Parameters
struct w1_master * dev the master device int bit 0 — write a 0, 1 — write a 0 read the level void w1_write_8 ( struct w1_master * dev, u8 byte ) В¶
Parameters
struct w1_master * dev the master device u8 byte the byte to write u8 w1_triplet ( struct w1_master * dev, int bdir ) В¶
- Does a triplet — used for searching ROM addresses.
Parameters
struct w1_master * dev the master device int bdir the bit to write if both id_bit and comp_bit are 0
Description
Return bits: bit 0 = id_bit bit 1 = comp_bit bit 2 = dir_taken
If both bits 0 & 1 are set, the search should be restarted.
Return
bit fields — see above
u8 w1_read_8 ( struct w1_master * dev ) В¶
Parameters
struct w1_master * dev the master device
Return
void w1_write_block ( struct w1_master * dev, const u8 * buf, int len ) В¶
Writes a series of bytes.
Parameters
struct w1_master * dev the master device const u8 * buf pointer to the data to write int len the number of bytes to write void w1_touch_block ( struct w1_master * dev, u8 * buf, int len ) В¶
Touches a series of bytes.
Parameters
struct w1_master * dev the master device u8 * buf pointer to the data to write int len the number of bytes to write u8 w1_read_block ( struct w1_master * dev, u8 * buf, int len ) В¶
Reads a series of bytes.
Parameters
struct w1_master * dev the master device u8 * buf pointer to the buffer to fill int len the number of bytes to read
Return
the number of bytes read
int w1_reset_bus ( struct w1_master * dev ) В¶
Issues a reset bus sequence.
Parameters
struct w1_master * dev the master device
Return
0=Device present, 1=No device present or error
int w1_reset_select_slave ( struct w1_slave * sl ) В¶
reset and select a slave
Parameters
struct w1_slave * sl the slave to select
Description
Resets the bus and then selects the slave by sending either a skip rom or a rom match. A skip rom is issued if there is only one device registered on the bus. The w1 master lock must be held.
Return
0=success, anything else=error
int w1_reset_resume_command ( struct w1_master * dev ) В¶
resume instead of another match ROM
Parameters
struct w1_master * dev the master device
Description
When the workflow with a slave amongst many requires several successive commands a reset between each, this function is similar to doing a reset then a match ROM for the last matched ROM. The advantage being that the matched ROM step is skipped in favor of the resume command. The slave must support the command of course.
If the bus has only one slave, traditionnaly the match ROM is skipped and a “SKIP ROM” is done for efficiency. On multi-slave busses, this doesn’t work of course, but the resume command is the next best thing.
The w1 master lock must be held.
void w1_next_pullup ( struct w1_master * dev, int delay ) В¶
register for a strong pullup
Parameters
struct w1_master * dev the master device int delay time in milliseconds
Description
Put out a strong pull-up of the specified duration after the next write operation. Not all hardware supports strong pullups. Hardware that doesn’t support strong pullups will sleep for the given time after the write operation without a strong pullup. This is a one shot request for the next write, specifying zero will clear a previous request. The w1 master lock must be held.
Return
0=success, anything else=error
void w1_write_bit ( struct w1_master * dev, int bit ) В¶
Generates a write-0 or write-1 cycle.
Parameters
struct w1_master * dev the master device int bit bit to write
Description
Only call if dev->bus_master->touch_bit is NULL
void w1_pre_write ( struct w1_master * dev ) В¶
Parameters
struct w1_master * dev the master device
Description
Pre-write operation, currently only supporting strong pullups. Program the hardware for a strong pullup, if one has been requested and the hardware supports it.
void w1_post_write ( struct w1_master * dev ) В¶
Parameters
struct w1_master * dev the master device
Description
Post-write operation, currently only supporting strong pullups. If a strong pullup was requested, clear it if the hardware supports them, or execute the delay otherwise, in either case clear the request.
u8 w1_read_bit ( struct w1_master * dev ) В¶
Generates a write-1 cycle and samples the level.
Parameters
struct w1_master * dev the master device
Description
Only call if dev->bus_master->touch_bit is NULL
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