comedi_dio_insn_config(9)

💫 comedi_dio_insn_config(9) — the Kernel API Manual glow-up

okay so bestie, welcome to the Kernel API Manual page for comedi_dio_insn_config, and trust me when I say this little function is doing so much behind the scenes for DIO subdevices 💅

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🌸 NAME 🌸

comedi_dio_insn_config — boilerplate (*insn_config) for DIO subdevices ✨

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🎀 SYNOPSIS 🎀

int comedi_dio_insn_config (struct comedi_device *dev , struct
       comedi_subdevice *s , struct comedi_insn *insn , unsigned int *data ,
       unsigned int mask );

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🦋 ARGUMENTS 🦋

• dev — the COMEDI device. the whole vibe, the main character 🫶
• s — the COMEDI subdevice. the specific little guy we're working on 💖
• insn — the COMEDI instruction. what you're asking it to do ✨
• data — instruction parameters and return data. it's giving input, it's giving output, it's giving both 😭
• mask — an io_bits mask for grouped channels, or 0 for a single channel 🎯

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⭐ DESCRIPTION ⭐

okay so here's the tea ☕ — if mask is 0, it gets replaced with a single-bit mask that matches the channel number given by insn->chanspec. literally just that one channel, no cap.

other than that, mask is for a group of channels — and that group should include the channel you specified — that are always configured together as inputs or as outputs. they're a package deal, bestie 🤝

this function partially handles the INSN_CONFIG_DIO_INPUT, INSN_CONFIG_DIO_OUTPUTS, and INSN_CONFIG_DIO_QUERY instructions:

• the first two (INSN_CONFIG_DIO_INPUT and INSN_CONFIG_DIO_OUTPUTS) update s->io_bits to record the directions of the masked channels 📝
• the last one (INSN_CONFIG_DIO_QUERY) sets data[1] to the current direction of that group of channels — COMEDI_INPUT or COMEDI_OUTPUT — the way it's recorded in s->io_bits 👑

🚨 important one: the caller is responsible for updating the DIO direction in the hardware registers if this function returns 0. like, this function sets you up, but you have to actually go do the hardware part. no skipping, fr fr 🙈

💀 return values (the vibe check)

• returns 0 for an INSN_CONFIG_DIO_INPUT or INSN_CONFIG_DIO_OUTPUT instruction ✅
• returns insn->n (which is > 0) for an INSN_CONFIG_DIO_QUERY instruction 🔥
• returns -EINVAL for some other instruction. not me getting rejected 💀

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🌈 SEE ALSO 🌈

kernel file ./drivers/comedi/drivers.c plus the whole friend group 💜:

comedi_set_hw_dev(9), comedi_alloc_devpriv(9), comedi_alloc_subdevices(9), comedi_alloc_subdev_readback(9), comedi_readback_insn_read(9), comedi_timeout(9), comedi_dio_update_state(9), comedi_bytes_per_scan_cmd(9), comedi_bytes_per_scan(9), comedi_nscans_left(9), comedi_nsamples_left(9), comedi_inc_scan_progress(9), comedi_handle_events(9), comedi_load_firmware(9), __comedi_check_request_region(9), comedi_check_request_region(9), comedi_legacy_detach(9), comedi_auto_config(9), comedi_auto_unconfig(9), comedi_driver_register(9), comedi_driver_unregister(9)

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and that's the page! 🧚 mwah 💋

this cutie lives over in ./drivers/comedi, dated October 2026, and it will forever be known as comedi_dio_insn_config(9) — slay, periodt 👑✨