linux-kernel - Re: [PATCH] thermal/drivers/of: Add a get_temp

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Date:   Tue, 28 May 2019 20:05:43 -0700
From:   Eduardo Valentin <edubezval@...il.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH] thermal/drivers/of: Add a get_temp_id callback function

On Thu, May 23, 2019 at 07:48:56PM -0700, Andrey Smirnov wrote:
> On Mon, Apr 29, 2019 at 9:51 AM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
> >
> > On 24/04/2019 01:08, Daniel Lezcano wrote:
> > > On 23/04/2019 17:44, Eduardo Valentin wrote:
> > >> Hello,
> > >>
> > >> On Tue, Apr 16, 2019 at 07:22:03PM +0200, Daniel Lezcano wrote:
> > >>> Currently when we register a sensor, we specify the sensor id and a data
> > >>> pointer to be passed when the get_temp function is called. However the
> > >>> sensor_id is not passed to the get_temp callback forcing the driver to
> > >>> do extra allocation and adding back pointer to find out from the sensor
> > >>> information the driver data and then back to the sensor id.
> > >>>
> > >>> Add a new callback get_temp_id() which will be called if set. It will
> > >>> call the get_temp_id() with the sensor id.
> > >>>
> > >>> That will be more consistent with the registering function.
> > >>
> > >> I still do not understand why we need to have a get_id callback.
> > >> The use cases I have seen so far, which I have been intentionally rejecting, are
> > >> mainly solvable by creating other compatible entries. And really, if you
> > >> have, say a bandgap, chip that supports multiple sensors, but on
> > >> SoC version A it has 5 sensors, and on SoC version B it has only 4,
> > >> or on SoC version C, it has 5 but they are either logially located
> > >> in different places (gpu vs iva regions), these are all cases in which
> > >> you want a different compatible!
> > >>
> > >> Do you mind sharing why you need a get sensor id callback?
> > >
> > > It is not a get sensor id callback, it is a get_temp callback which pass
> > > the sensor id.
> > >
> > > See in the different drivers, it is a common pattern there is a
> > > structure for the driver, then a structure for the sensor. When the
> > > get_temp is called, the callback needs info from the sensor structure
> > > and from the driver structure, so a back pointer to the driver structure
> > > is added in the sensor structure.
> >

Do you mind sending a patch showing how one could convert an existing
driver to use this new API?

> > Hi Eduardo,
> >
> > does the explanation clarifies the purpose of this change?
> >
> 
> Eduardo, did you ever have a chance to revisit this thread? I would
> really like to make some progress on this one to unblock my i.MX8MQ
> hwmon series.

The problem I have with this patch is that it is an API which resides
only in of-thermal. Growing APIs on DT only diverges of-thermal from
thermal core and platform drivers.

Besides, this patch needs to document the API in Documention/

> 
> Thanks,
> Andrey Smirnov