comedi_request_region(9)

💅 comedi_request_region(9) — Kernel API Manual ✨

okay bestie, welcome to comedi_request_region, the function that bags you an I/O region for a legacy driver 🎀 this is the 9 section of the Kernel API Manual, so like, kernel-internals territory, hydrate first 💖

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🌸 NAME 🌸

comedi_request_region — request an I/O region for a legacy driver 👑

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✨ SYNOPSIS ✨

int comedi_request_region (struct comedi_device *dev , unsigned long
start , unsigned long len );

literally three args, she's lowkey simple, iykyk 🦋

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🫶 ARGUMENTS 🫶

• dev — the COMEDI device. the main character of this whole situation 🌟
• start — base address of the I/O region. like where it starts, obviously 💅
• len — length of the I/O region. how much of it you're claiming, no cap 📏

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🔥 DESCRIPTION 🔥

okay so this one requests the specified I/O port region — and heads up, that region must start at a non-zero address. zero is not the vibe, zero gets rejected 🙈

on success, dev->iobase is set to the base address of the region, and dev->iolen is set to its length. she files her paperwork correctly, we love that for her 📋✨

and the returns? iconic behaviour, honestly:

• returns 0 on success — slay 💚
• returns -EINVAL if start is 0 — yeah bestie, told you, non-zero only 💀
• returns -EIO if the request fails — it happens, we move on 😭

fr fr, don't pass 0 as start, that's a guaranteed -EINVAL and you'll be crying in the group chat 🥲

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👑 SEE ALSO 👑

so there's a whole friend group here, and they're all important, so we're listing every single one, no skipping, periodt 💜

• the kernel file ./include/linux/comedi/comedidev.h — go read it, it's giving main character energy 📖
• struct comedi_subdevice(9)
• struct comedi_buf_page(9)
• struct comedi_buf_map(9)
• struct comedi_async(9)
• enum comedi_cb(9)
• struct comedi_driver(9)
• struct comedi_device(9)
• struct comedi_lrange(9)
• comedi_range_is_bipolar(9)
• comedi_range_is_unipolar(9)
• comedi_range_is_external(9)
• comedi_chan_range_is_bipolar(9)
• comedi_chan_range_is_unipolar(9)
• comedi_chan_range_is_external(9)
• comedi_offset_munge(9)
• comedi_bytes_per_sample(9)
• comedi_sample_shift(9)
• comedi_bytes_to_samples(9)
• comedi_samples_to_bytes(9)
• comedi_check_trigger_src(9)
• comedi_check_trigger_is_unique(9)
• comedi_check_trigger_arg_is(9)
• comedi_check_trigger_arg_min(9)
• comedi_check_trigger_arg_max(9)
• comedi_buf_n_bytes_ready(9)
• __comedi_request_region(9)
• module_comedi_driver(9)

that's the whole squad, all 28 of them, go say hi 🫶💖

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kisses bestie, the source path is <code>./include/linux/comedi</code> and this edition is stamped October 2026 — go request some I/O regions responsibly and drink some water 💜🎀🌈