COMEDI_GET_CLOCK_SOU(3)

💖 comedi_get_clock_source — get the master clock for a subdevice 💖

okay bestie, welcome to the Comedi reference page for comedi_get_clock_source(3) ✨ (yes, the manual is literally named COMEDI_GET_CLOCK_SOU(3), the terminal just cuts it off, it's giving ctrl-c on the title ngl). Sit down, grab a boba 🧋, and let's find out what clock your subdevice is running on 🕐💅

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✨ NAME ✨

comedi_get_clock_source — get the master clock for a subdevice

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🦋 SYNOPSIS 🦋

#include <comedilib.h>

int comedi_get_clock_source(comedi_t * device, unsigned int subdevice,
                            unsigned int channel, unsigned int * clock,
                            unsigned int * period_ns);

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🎀 STATUS 🎀

alpha 🍼 — yeah she's still in her alpha era, handle with care-ish, but we love her anyway.

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🌸 DESCRIPTION 🌸

So basically 💁‍♀️ this function goes and queries the master clock for a subdevice — aka the clock that comedi_set_clock_source already set up earlier. Think of it like asking your subdevice "hey girl, what time is it for you?" 🕵️‍♀️

The master clock that's currently configured gets written to *clock ✍️. And here's the tea: the possible values and what clock each one actually corresponds to are driver-dependant — so it depends on which driver you're running, no cap 🚫🧢.

The period of the clock, in nanoseconds, gets written to *period_ns. If that period is unknown, you just get a literal zero 0 in there, and honestly? relatable, sometimes we don't know our own period either 😭🩸

Now, if your subdevice doesn't support configuring its master clocks on a per-channel basis, then the channel parameter just gets ignored. It's giving "I don't see you" energy 🙈 — not personal, it's just how the hardware is set up.

It is safe to pass NULL pointers as the clock or period_ns parameters 🫶 — so if you only care about one of them, go off, pass NULL for the other, she won't crash.

⚠️ important vibe check: this function is only useable on subdevices that provide support for the INSN_CONFIG_GET_CLOCK_SRC configuration instruction. If your subdevice doesn't do that, it's not happening bestie 💀

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👑 RETURN VALUE 👑

• 0 — on success 🎉 slay, you got your clock
• -1 — on error 😔 something went wrong

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💜 AUTHORS 💜

The iconic legends who made this happen, we stan 🫶:

• 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. 👑

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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 📚. And quick side note for the legal girlies: 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 — like, literally none. Not even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE 💀. See the GNU Lesser General Public License for more details, bestie, please read it fr fr 📖

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 📬🫶

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aaaaand that's the whole page! 💅 This was Comedi, dated 03/20/2026, for the manual page COMEDI_GET_CLOCK_SOU(3) — go get those clocks, main character 🕐👑✨ bye bestie, ily, gn 🎀🦋