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

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Message-ID: <d97c57bc-dfe0-74cf-4266-a2f223cc5d24@nokia.com>
Date:   Mon, 23 Oct 2017 09:54:26 +0200
From:   Romain Porte <romain.porte@...ia.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [1/2] pmbus: added tps544c20 driver with trimming support

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).
My point is that I am exactly using Linux's pmbus implementation in 
order to perform a manufacturing calibration which is indeed a one-time 
operation.

I agree that exposing these sysfs entries to end users can be dangerous. 
It can be useful if you actually want to perform a component calibration 
using Linux. Actually I am running an userspace application that does 
the calibration by writing to these sysfs entries. This driver is useful 
for manufacturing calibration and I think can be useful for other Linux 
users who wants to perform this kind of operation too.

If this driver is dangerous for the end-user, how can we keep the 
features of this driver for manufacturing calibration using Linux? Maybe 
keep the generic driver for normal use and propose this specific driver 
as 'Advanced TPS544C20 driver [DANGER]'?

Romain.