From: Emil Lenngren <emil.lenngren@gmail.com>
To: linux-pwm@vger.kernel.org
Subject: Atomic update of period and duty_cycle in sysfs
Date: Mon, 7 Jun 2021 15:47:36 +0200 [thread overview]
Message-ID: <CAO1O6seyi+1amAY5YLz0K1dkNd7ewAvot4K1eZMpAAQquz0-9g@mail.gmail.com> (raw)
Hi everyone,
I don't know if this has been proposed before, but I propose a
period_and_duty_cycle attribute in sysfs, beyond period and
duty_cycle, that could be used if both period and duty cycle should be
updated at the same time.
When we programmatically want to update these values, it can currently
be a bit tricky to get this correct, since if we write the two
attributes in the "wrong" order we could end up in a situation where a
write gets EINVAL as result, depending on the current values, since it
must always be the case that duty_cycle <= period. We also have the
issue that writing one file at the time doesn't result in an atomic
update, so potentially the user can observe a strange behaviour from
the pwm between the two writes, because for example the old period is
used but the new duty_cycle is used for a short amount of time.
A period_and_duty_cycle attribute would fix this, where the two values
are space-separated.
/Emil
reply other threads:[~2021-06-07 13:48 UTC|newest]
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