linux-kernel - Re: [PATCH v2] hwmon: corsair-psu: add reporting of rail mode via debugfs

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Date:   Thu, 11 Aug 2022 08:05:06 +0000
From:   Wilken Gottwalt <wilken.gottwalt@...teo.net>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-kernel@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v2] hwmon: corsair-psu: add reporting of rail mode via
 debugfs

On Wed, 10 Aug 2022 11:21:36 -0700
Guenter Roeck <linux@...ck-us.net> wrote:

> On 8/10/22 10:48, Wilken Gottwalt wrote:
> > On Wed, 10 Aug 2022 10:29:08 -0700
> > Guenter Roeck <linux@...ck-us.net> wrote:
> > 
> >> On 8/10/22 09:56, Wilken Gottwalt wrote:
> >>> On Wed, 10 Aug 2022 09:31:21 -0700
> >>> Guenter Roeck <linux@...ck-us.net> wrote:
> >>>
> >>>> On 8/10/22 06:53, Wilken Gottwalt wrote:
> >>>>> Add reporting if the PSU is running in single or multi rail mode via
> >>>>> ocpmode debugfs entry. Also update the documentation accordingly.
> >>>>>
> >>>>> Signed-off-by: Wilken Gottwalt <wilken.gottwalt@...teo.net>
> >>>>> ---
> >>>>> Changes in v2:
> >>>>>      - fixed spelling issues in commit message
> >>>>
> >>>> You did not address or even provide feedback on my second comment.
> >>>
> >>> Oh darn ... sorry, I was quite busy and didn't really pay attention. I will
> >>> answer the earlier mail and think about it.
> >>>
> >>> Though, maybe you can help me with that what keeps me so busy. Would it be okay
> >>> to use a kthread in a hwmon driver to do sampling (500ms - 10s) in conjunction
> >>> with HWMON_C_UPDATE_INTERVAL, or is this a strict no-no? I know it is actually
> >>> used to set a sample/update rate in a sensor (-register), but this USB-HID
> >>> approach is a pure polling thing. It seems to work quite and enables the driver
> >>> to collect data quite early in the boot process.
> >>>
> >>
> >> It really depends. Is it _necessary_ ? The pwm-fan driver uses a timer for
> >> periodic polling, but that is because it has to. We should not do it purely
> >> for convenience, and from the code I don't immediately see why it would
> >> be necessary.
> > 
> > Together with the polling I would add encountered lowest and highest values and
> > the average of basically all available sensors (kind of session statistics). I
> > know it is a bit odd, but currently these power supplies are sold again in a
> > newer version and people really like to use them in their servers/workstations
> > because of the "realtime" data and this driver. No joke, but I really got
> > several requests to add this and I must admit I have quite some fun implementing
> > it.
> > 
> 
> That is out of scope for a kernel driver. If desired, a user space application
> should do the polling and calculate statistics such as lowest/highest or averages.

That is exactly what I told the requesting people. Now it is in the public
record and I hope that kind of requests go down a bit, at least for pushing
this in the mainline kernel.

greetings,
Wilken