STRUCT W1_BUS_MASTER(9)

Okay bestie, welcome to struct w1_bus_master(9) from the Kernel API Manual ✨. This is the whole ops vibe for a bus master, and we’re gonna go through every single member together, no skips, fr fr 💖.

✨ NAME ✨

struct w1_bus_master — operations available on a bus master. That’s the glow-up: it’s the set of operations you get on a bus master, periodt 👑.

🌸 SYNOPSIS 🌸

Here’s the struct in all its iconic form — copy it exactly, bestie:

       struct w1_bus_master {
           void *data;
           u8 (*read_bit)(void *);
           void (*write_bit)(void *, u8);
           u8 (*touch_bit)(void *, u8);
           u8 (*read_byte)(void *);
           void (*write_byte)(void *, u8);
           u8 (*read_block)(void *, u8 *, int);
           void (*write_block)(void *, const u8 *, int);
           u8 (*triplet)(void *, u8);
           u8 (*reset_bus)(void *);
           u8 (*set_pullup)(void *, int);
           void (*search)(void *, struct w1_master *, u8,
       w1_slave_found_callback);
           char *dev_id;
        };

💅 Members 💅

• data — the first parameter in all the functions below. The main-character pointer, basically 🫶.
• read_bit — sample the line level, then 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 byte. 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 handle the different types of ROM search. w1_master* is passed to the slave found callback. The 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. No cap, that’s the rule 💀.

👀 SEE ALSO 👀

Kernel file ./include/linux/w1.h:

• struct w1_reg_num(9)
• struct w1_slave(9)
• enum w1_master_flags(9)
• struct w1_master(9)
• struct w1_family_ops(9)
• struct w1_family(9)
• module_w1_family(9)

Signed off with love from ./include/linux — October 2026 — struct w1_bus_master(9) 💖🦋✨