lm75 on i2c-elektor.c

lm75 on i2c-elektor.c

[Magnus Lindholm]

Hi,

I was playing around with lm_sensors on my UP2000 Alpha board and things work
pretty well, right out of the box. I noticed that the i2c-elektor.c
stuff gets disabled
when building a SMP kernel, does anyone know why that is?
i2c/busses/Kconfig says I2C_ELEKTOR BROKEN_ON_SMP.

Regards

Magnus Lindhom

Re: lm75 on i2c-elektor.c

[Wolfram Sang]

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> when building a SMP kernel, does anyone know why that is?

In history.git, I found 51e9e9743877660198565a86034ca72de73dcf7e from
2003 which adds BROKEN_ON_SMP. Commit message says:

    - let all drivers that don't compile on SMP (due to cli/sti usage)
      depend on a BROKEN_ON_SMP that is only defined if !SMP || BROKEN

But then again, there is also 4b16dac1d9 ("[PATCH] i2c-elektor: get rid
of cli/sti") from 2004 which converts the driver from cli/sti to
spinlocks. Maybe it just works now?


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Re: lm75 on i2c-elektor.c

[Magnus Lindholm]

> But then again, there is also 4b16dac1d9 ("[PATCH] i2c-elektor: get rid
> of cli/sti") from 2004 which converts the driver from cli/sti to
> spinlocks. Maybe it just works now?
>

I've been running it for a day or so on my UP2000+ Alpha with an SMP
kernel and haven't seen any issues (I manually removed the
BROKEN_ON_SMP from Kconfig). I guess I can keep testing it for a
while and if everything seems fine I can submit a patch to remove the
BROKEN_ON_SMP?


/Magnus

Re: lm75 on i2c-elektor.c

[Wolfram Sang]

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> I've been running it for a day or so on my UP2000+ Alpha with an SMP
> kernel and haven't seen any issues (I manually removed the
> BROKEN_ON_SMP from Kconfig). I guess I can keep testing it for a
> while and if everything seems fine I can submit a patch to remove the
> BROKEN_ON_SMP?

Yes. If possible, stress-test I2C communication a bit. But with the
spinlocks, I am optimistic anyhow.


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Re: lm75 on i2c-elektor.c

[Magnus Lindholm]

Hi,

It's running stable so far, Wolfram, the git history references that
you mentioned,
they are not in torvalds linux git repo? I could only find history
there dating back
to 2005.


/Magnus¨

Re: lm75 on i2c-elektor.c

[Wolfram Sang]

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> they are not in torvalds linux git repo? I could only find history
> there dating back to 2005.

history.git is a dedicated tree, built after the facts ;)

https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/

Fun to browse for such questions...


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Re: lm75 on i2c-elektor.c

[Magnus Lindholm]

Hi,

Thanks! I've been running the driver on SMP kernel for a few days now
sending i2c data from all sensors to influx/grafana and everything seems
stable. I'll send out a patch later for review. I believe we can just
allow this driver to be built on SMP kernels.

Magnus

On Fri, Nov 21, 2025 at 8:24 AM Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
>
>
> > they are not in torvalds linux git repo? I could only find history
> > there dating back to 2005.
>
> history.git is a dedicated tree, built after the facts ;)
>
> https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/
>
> Fun to browse for such questions...
>