Re: IIO Driver for TMP117 Temperature sensor

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Mon, 14 Dec 2020 01:44:20 +0530
Puranjay Mohan <puranjay12@gmail.com> wrote:

> On Sun, Dec 13, 2020 at 10:20 PM Jonathan Cameron <jic23@kernel.org> wrote:
> >
> > On Sun, 13 Dec 2020 08:08:26 -0800
> > Guenter Roeck <linux@roeck-us.net> wrote:
> >  
> > > On 12/13/20 7:12 AM, Jonathan Cameron wrote:  
> > > > On Wed, 9 Dec 2020 11:48:40 -0800
> > > > Guenter Roeck <linux@roeck-us.net> wrote:
> > > >  
> > > >> On 12/9/20 12:11 AM, Alexandru Ardelean wrote:  
> > > >>> On Tue, Dec 8, 2020 at 6:10 PM Puranjay Mohan <puranjay12@gmail.com> wrote:  
> > > >>>>
> > > >>>> I have this TI's TMP117 sensor with me and I was thinking about writing an
> > > >>>> IIO driver for it as a hobby project. Is the IIO subsystem the correct
> > > >>>> place for this driver? if yes, can someone help me get started with this,
> > > >>>> I haven't written an IIO driver before. I have this sensor and also a
> > > >>>> raspberry pi with me for testing.  
> > > >>>
> > > >>> This could also fit into drivers/hwmon.
> > > >>> Looking at the HWMON subsystem there are more TMP drivers there
> > > >>> (TMP102/103/108/401/513).
> > > >>> The first 3 seem a bit more similar to TMP117 (in terms of register map).
> > > >>>  
> > > >>
> > > >> It would probably be better suited for hwmon (it has limit registers,
> > > >> suggesting a common use as hardware monitoring device).  
> > > > It is a curious part.  I suspect TI based their design for a medical grade
> > > > digital thermometer chip on an existing hwmon part.
> > > >
> > > > The limit registers are very simple so could be supported by IIO.
> > > > This sits somewhere in the middle of high end thermocouple chips which
> > > > tend to be in IIO and typically lower accuracy / range hwmon parts.
> > > >
> > > > It's in the fuzzy borderline region so I doubt anyone would raise strong
> > > > objections to which subsystem it was in.  Guenter has fallen on the
> > > > hwmon side of things and I'm fine with that.
> > > >  
> > >
> > > On the other side, it turns out that there is already tmp107 support
> > > in iio, and tmp107 is pretty much the spi equivalent of the same chip.
> > > So it really depends on the use case. If the user wants to use the iio
> > > subsystem, I am fine with it. We just need to remind people that this
> > > implies no or only limited hwmon support.
> > >
> > > [ I really need to spend the time to write a hwmon->iio bridge.
> > >   The iio->hwmon bridge is a bit limited - I have not been able to
> > >   figure out how to support limit registers (or event values)
> > >   and events, and I don't think it is possible. ]  
> >
> > So far IIO doesn't have an in kernel consumer interface for
> > events. It shouldn't be that hard to add one though and it
> > has been on the todo list for a very long time.  We've discussed
> > it a few times and concluded that there are some short cuts such
> > as sending all events to all consumers and relying on the receiver
> > to do any necessary filtering. It's a bit messy but it makes for
> > much simpler core code.
> >
> > Maybe I'll get bored enough over xmas to look at it...
> >  
> 
> Hi Jonathan,
> Where can I access this TODO list, I would like to do some tasks on it.
> I am a novice but I might be able to solve the easier tasks.

Sadly I'm rubbish at keeping an up to date list.  So this tends
to be scattered across numerous ancient discussions.

I do occasionally send out such a document, though I haven't done
so for some time.  I'll see if I can do a refresh sometime in next
month or so.

Thanks,

Jonathan

> 
> > Jonathan
> >  
> > >
> > > Guenter
> > >  
> > > > Jonathan
> > > >  
> > > >>  
> > > >>> Let's see what others have to add.
> > > >>> But, all-in-all whatever driver you end up writing, the easiest method
> > > >>> is to copy an existing similar driver and extend it.
> > > >>> Sometimes, a part can be added to an existing driver.
> > > >>> At a quick scan through existing drivers, it doesn't look like TMP117
> > > >>> is similar to existing drivers, so it may require a new driver
> > > >>> altogether.  
> > > >>
> > > >> I don't see an immediate match either, but the tmp102 hwmon driver
> > > >> might be a good start.
> > > >>
> > > >> Guenter
> > > >>  
> > > >>> I may have missed something though.
> > > >>>
> > > >>> Thanks
> > > >>> Alex
> > > >>>  
> > > >>>>
> > > >>>> --
> > > >>>> Thanks and Regards
> > > >>>>
> > > >>>> Yours Truly,
> > > >>>>
> > > >>>> Puranjay Mohan  
> > > >>  
> > > >  
> > >  
> >  
> 
>