COMEDI_DIO_BITFIELD2(3)

💖 COMEDI_DIO_BITFIELD2 💖

okay bestie, sit down, we're reading a whole Comedi reference page together and it's gonna be iconic. this is comedi_dio_bitfield2, from section 3 of the Comedi manual, and it's your girl's fave way to touch a whole bunch of digital channels at once. no cap. 🦋

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✨ NAME ✨

comedi_dio_bitfield2 — read/write multiple digital channels. yes, multiple, plural, we're not doing them one at a time like it's 1998. 💅

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🌸 SYNOPSIS 🌸

#include <comedilib.h>

int comedi_dio_bitfield2(comedi_t * device, unsigned int subdevice,
                         unsigned int write_mask, unsigned int * bits,
                         unsigned int base_channel);

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👑 DESCRIPTION 👑

so here's the tea. comedi_dio_bitfield2 lets you read or write a bunch of channels together on a digital input device, a digital output device, or a configurable digital I/O device. group project energy, but make it hardware. 🫶

the parameter write_mask and the value that bits points to are both interpreted as bit fields — and the least significant bit is the one that represents channel base_channel. like, that's the anchor point, everything else stacks up from there. ⭐

for every bit in write_mask that's set to 1, the matching bit in *bits gets written out to the corresponding digital output channel. slay, that's the write half.

then, after all the output channels have been written, every channel gets read, and the result goes into the appropriate bits in *bits. and here's the lil detail people always forget: the result of reading an output channel is the last value written to that output channel. it's giving "you get back what you gave it." 💀

⚠️ real talk — all the channels might not be read or written at the exact same time. not a glow-up moment, just how it is. for example, the driver may need to sequentially write to several registers in order to set all the digital channels specified by the write_mask and base_channel parameters. so like, it's a conceptual all-at-once, not a literal one. lowkey important. 😭

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🔥 RETURN VALUE 🔥

if everything went great, 0 is returned. otherwise, -1. that's it, that's the whole vibe check. 💜

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🎀 AUTHORS 🎀

the main characters who made this happen:

• David Schleef <ds@schleef.org> — Author.
• Frank Mori Hess <fmhess@users.sourceforge.net> — Author.
• Herman Bruyninckx <Herman.Bruyninckx@mech.kuleuven.ac.be> — Author.
• Bernd Porr <tech@linux-usb-daq.co.uk> — Author.
• Ian Abbott <abbotti@mev.co.uk> — Author.
• Éric Piel <piel@delmic.com> — Author.

all of them, legends, no notes. 👑

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🌈 COPYRIGHT 🌈

Copyright © 1998-2003 David Schleef Copyright © 2001-2003, 2005, 2008 Frank Mori Hess Copyright © 2002-2003 Herman Bruyninckx Copyright © 2012 Bernd Porr Copyright © 2012 Ian Abbott Copyright © 2012, 2015 Éric Piel

This document is part of Comedilib. In the context of this document, the term "source code" as defined by the license is interpreted as the XML source.

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, version 2.1 of the License.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.

🚨 bestie pls read that warranty bit again. there is literally no warranty. it's LGPL 2.1 and it's doing its best. do not @ me. 💖

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and that's the whole page!! this one came from the Comedi reference manual, version dated 03/20/2026 — save it, cite it, love it. bye pookie, go write some bit fields 💅✨🎀