linux-kernel - Re: [1/2] pmbus: added tps544c20 driver with trimming support

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Date:   Mon, 23 Oct 2017 15:17:02 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Romain Porte <romain.porte@...ia.com>
Cc:     linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [1/2] pmbus: added tps544c20 driver with trimming support

On Mon, Oct 23, 2017 at 03:34:24PM +0200, Romain Porte wrote:
> On 21/10/2017 18:20, Guenter Roeck wrote:
> >This should be part of device programming in manufacturing, just like,
> >say, current calibration. It should not be user programmable, even less so
> >runtime programmable. On top of that, we definitely don't want to make
> >STORE_USER_ALL available to user space. Both can too easily result in
> >a bricked device (bad enough that the register values are writable using
> >i2cset).
> After some work, I have tested accessing these registers using i2cget and
> i2cset and I can reproduce all the features I have implemented in this
> driver. I think am going to re-implement my calibration procedure using
> i2cget and i2cset in userspace.
> 
> I thought it could be a good idea to make this accessible by sysfs entries.
> Since one must read the datasheet for calibrating the component, I guess it
> is not a big deal to have users to find register addresses/sizes and write
> to them using userspace commands instead of (over?)simplifying it by
> providing dedicated sysfs entries.
> 
Anyone tasked with calibration type work on any chip should _really_ read
the datasheet.

Guenter