comedi_readback_insn_read(9)

🌸 comedi_readback_insn_read(9) 🌸

okay so bestie, welcome to the Kernel API Manual ✨ — yes this is a real kernel manpage, no I'm not kidding, and yes we're gonna get through it together 💖

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🎀 NAME 🎀

comedi_readback_insn_read — literally the generic (*insn_read) for subdevice readback 🫶 like that's its whole job and it does it slayfully

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✨ SYNOPSIS ✨

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

that's the whole vibe right there 👑

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🌸 ARGUMENTS 🌸

• dev — the COMEDI device 💜
• s — the COMEDI subdevice 🦋
• insn — the COMEDI instruction ⭐
• data — pointer where the readback data gets returned, so like, this is where the good stuff lands 📬

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💅 DESCRIPTION 💅

so what this cutie actually does: it handles the INSN_READ instruction for subdevices that use the readback array allocated by comedi_alloc_subdev_readback. iconic of it honestly 🌈

you can use it directly as the subdevice's handler (s->insn_read) or call it via a wrapper — dealer's choice, both valid, we love flexibility 💖

now listen, about insn->n: it's normally 1, which will read a single value. lowkey the standard. but if it's higher? then the same element of the readback array gets read multiple times. not different elements. the same one. repeatedly. that's the whole bit, no cap 🫶

returns insn->n on success ✨ — or -EINVAL if s->readback is NULL, because bestie there's nothing to read back, that's an error, periodt 💀

fr fr note: if s->readback is NULL you get -EINVAL. no readback array = no reads. it's giving "empty handed" 🙈

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🔥 SEE ALSO 🔥

oh we got a whole friend group here, all from the kernel file ./drivers/comedi/drivers.c 🧚 — say hi to:

• comedi_set_hw_dev(9)
• comedi_alloc_devpriv(9)
• comedi_alloc_subdevices(9)
• comedi_alloc_subdev_readback(9)
• comedi_timeout(9)
• comedi_dio_insn_config(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)

like I said. whole friend group. main character energy from start to finish 👑

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and that's the page!! mwah 💋 this lil manual lives under the source dir ./drivers/comedi, dated October 2026 — so yeah, mark your calendar bestie, and go read some subdevice readback data for me 🍓✨💜