comedi_bytes_per_scan_cmd(9)

💅 comedi_bytes_per_scan_cmd(9) — the Kernel API Manual era 🎀

okay so bestie, gather round, because we're diving into comedi_bytes_per_scan_cmd from the Kernel API Manual and honestly? it's giving "small function, big responsibilities" ✨

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🌸 NAME 🌸

comedi_bytes_per_scan_cmd — literally just tells you the length of an asynchronous command "scan" in bytes 💖

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✨ SYNOPSIS ✨

unsigned int comedi_bytes_per_scan_cmd (struct comedi_subdevice *s ,
struct comedi_cmd *cmd );

two arguments, one unsigned int coming back at you, no drama 🫶

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🎀 ARGUMENTS 🎀

• s — the COMEDI subdevice. yes queen, that one 💅
• cmd — the COMEDI command. the actual command in question, bestie 🦋

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🔥 DESCRIPTION 🔥

so what does it do? it determines the overall scan length according to the subdevice type and the number of channels in the scan for the specified command. that's the whole vibe check 🔍

for digital input, output or input/output subdevices, samples for multiple channels are assumed to be packed into one or more unsigned short or unsigned int values according to the subdevice's SDF_LSAMPL flag. packed! like a cute little lunchbox 🍓

for other types of subdevice, samples are assumed to occupy a whole unsigned short or unsigned int according to the SDF_LSAMPL flag. one sample, one whole value, no sharing, main character energy only 👑

and then — drumroll — it returns the overall scan length in bytes 🌈

ngl the SDF_LSAMPL flag is doing a LOT of heavy lifting in this paragraph, so keep an eye on it 👀

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💜 SEE ALSO 💜

• the Kernel file ./drivers/comedi/drivers.c 📁
• 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_insn_config(9)
• comedi_dio_update_state(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, the whole friend group showed up 😭🫶

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and that's the page!! this lil section lives in ./drivers/comedi, dated October 2026, and it's all under the comedi_bytes_per_scan_cmd(9) header — stay hydrated, read your manpages, mwah 💋💖