__comedi_request_region(9)

🌸 __comedi_request_region (9) — Kernel API Manual 💅

okay so bestie, welcome to the group chat for __comedi_request_region(9), straight out of the Kernel API Manual, section 9. this one's a little legend hidden in the kernel headers and honestly it's giving "small but mighty" energy 🫶

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✨ NAME ✨

__comedi_request_region — Request an I/O region for a legacy driver 👑

like, it's the girl who books the venue for the old-school drivers. literally her whole job 💖

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🎀 SYNOPSIS 🎀

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

that's the whole vibe check right there — three args, one int coming back at you 😭

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💅 ARGUMENTS 💅

• dev — the COMEDI device. your main character ✨
• start — the base address of the I/O region. where the party starts 📍
• len — the length of the I/O region. how long the party lasts 🎉

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🦋 DESCRIPTION 🦋

So basically: it requests the specified I/O port region, and that region must start at a non-zero address. not zero. never zero. zero is not invited 🚫💀

Here's the receipts on what you get back, no cap:

• Returns 0 on success — ate, no notes 👑
• -EINVAL if start is 0 — like I said, zero is not invited 🙈
• -EIO if the request fails — it's giving "we tried, bestie" 😭

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🌈 SEE ALSO 🌈

the whole friend group fr fr — go say hi 💜

Kernel file ./include/linux/comedi/comedidev.h

• 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)

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bestie reminder: that start address has to be non-zero. that's the whole plot twist. -EINVAL is literally waiting for you if you forget 🫶

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and that's the page!! mwah 💋 — brought to you by the file ./include/linux/comedi, dated October 2026, and it's still __comedi_request_region(9) forever and always 🧚‍♀️💜