STRUCT COMEDI_BUFINFO(9)

✨ struct comedi_bufinfo(9) ✨

okay bestie, buckle up 💖 this is a page from the Kernel API Manual (that's the manual name, slay) and it's all about one lil struct that lets you mess with buffer positions for a subdevice. it's giving "small but important" energy, no cap.

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🎀 SYNOPSIS 🎀

like, here's the whole vibe of the struct, literally verbatim, don't touch:

struct comedi_bufinfo {
    unsigned int subdevice;
    unsigned int bytes_read;
    unsigned int buf_write_ptr;
    unsigned int buf_read_ptr;
    unsigned int buf_write_count;
    unsigned int buf_read_count;
    unsigned int bytes_written;
    unsigned int unused[4];
 };

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🌸 Members 🌸

okay so every single field, let's go 🫶

• subdevice — the subdevice index. which subdevice you're talking about, iykyk.
• bytes_read — you use this to specify how much to advance the read position for an asynchronous command in the input ("read") direction. it's giving "move the read pointer this far" 💅
• buf_write_ptr — the current write position (index) within the buffer. where the writing is at, right now.
• buf_read_ptr — the current read position (index) within the buffer. where the reading is at, right now.
• buf_write_count — total amount written, modulo 2^32. yes, the modulo is real 🔥
• buf_read_count — total amount read, modulo 2^32. same energy, read edition.
• bytes_written — you use this to specify how much to advance the write position for an asynchronous command in the output ("write") direction. the write-side twin of bytes_read ✨
• unused — reserved for future use. it's literally just sitting there, main character energy, waiting for its moment 🌈

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💜 Description 💜

so this whole struct is used with the COMEDI_BUFINFO ioctl, and it does two iconic things:

• optionally advance the current read or write position in an asynchronous acquisition data buffer (yes, optionally — you don't have to, it's chill)
• get the current read and write positions in the buffer

that's it, that's the tea. two jobs, both ate. 💅

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🦋 SEE ALSO 🦋

the kernel file is ./include/uapi/linux/comedi.h, and it's friends with literally everyone. here's the full squad, no skips:

• enum comedi_subdevice_type(9)
• enum comedi_io_direction(9)
• enum configuration_ids(9)
• enum comedi_digital_trig_op(9)
• enum comedi_support_level(9)
• enum comedi_counter_status_flags(9)
• struct comedi_insn(9)
• struct comedi_insnlist(9)
• struct comedi_cmd(9)
• struct comedi_chaninfo(9)
• struct comedi_rangeinfo(9)
• struct comedi_krange(9)
• struct comedi_subdinfo(9)
• struct comedi_devinfo(9)
• struct comedi_devconfig(9)
• struct comedi_bufconfig(9)

like, that's a whole group chat right there 💀 but go read them, fr fr.

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ngl bestie, the struct has unused[4] and it means it — reserved for future use, so don't go writing your own lore into it 🙈

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🌸 okay bye, this page lives in ./include/uapi/linux, dated October 2026, and it's struct comedi_bufinfo(9) — go forth and advance those buffer positions, you absolute icon 👑💖