COMEDI_SET_CLOCK_SOU(3)

✨ COMEDI_SET_CLOCK_SOU — bestie edition ✨

okay so this is a page from the Comedi reference manual, section 3, and it's about comedi_set_clock_source. clock lore incoming 💖

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🌸 NAME 🌸

comedi_set_clock_source — set the master clock for a subdevice 👑

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🎀 SYNOPSIS 🎀

#include <comedilib.h>

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

like, that's the whole vibe. five arguments, one int back. slay ✨

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🦋 STATUS 🦋

alpha 💅

(yeah bestie, it's giving experimental. tread lightly, it's still growing into itself.)

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💜 DESCRIPTION 💜

so this function picks out a master clock for a subdevice. that's the whole job. the clock parameter is what selects the master clock, and bestie — it's driver-dependant. no universal list, it depends on your driver, iykyk.

here's the tea on channel: if the subdevice doesn't support configuring its master clocks on a per-channel basis, then the channel parameter just gets ignored. gone. not a thought. 🙈

then there's period_ns, which specifies the clock's period in nanoseconds. you can leave it unspecified by passing a value of zero. drivers will ignore the clock period if they already know what the clock period should be for the specified clock — like, for an on-board 20MHz oscillator, they already know, so they're not even listening. 💀

but!! certain boards that use a phase-locked loop to synchronize to external clock sources must be told the period of the external clock. no period, no sync, periodt. and specifying a clock period for an external clock may also allow the driver to support TRIG_TIMER sources in commands while using the external clock. cute, right? 🔥

if you wanna know what clock is currently set, you can query it with the comedi_get_clock_source function. 🫶

⚠️ important: this function is only useable on subdevices that provide support for the INSN_CONFIG_SET_CLOCK_SRC configuration instruction. no support, no clock-setting, no exceptions.

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🌈 RETURN VALUE 🌈

• 0 on success 🎉
• -1 on error 😭

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👑 AUTHORS 👑

the icons 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.

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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. (yes bestie, that's the all-caps part, it's serious and we respect it 🙏)

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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and that's the page!! 💖 this was the Comedi reference, page COMEDI_SET_CLOCK_SOU(3), dated 03/20/2026, brought to you by Comedi. go set some clocks, bestie, you've got this 🫶✨🎀