[lm-sensors] local macro

Jean Delvare khali at linux-fr.org
Wed Oct 6 23:32:21 CEST 2010


On Wed, 6 Oct 2010 14:02:26 -0700, Guenter Roeck wrote:
> On Wed, 2010-10-06 at 15:54 -0400, Paul Thomas wrote:
> > > No, both of those are runtime options internal to the ads7871, and
> > > because we initiate a read by setting that register anyway there isn't
> > > any additional setup cost (at least there isn't any spi cost, there is
> > > a little additional code in show_voltage).
> > >
> This isn't a matter of cost, but a matter of maintaining a consistent
> ABI.
> 
> A brief look into the datasheet shows that the chip is a generic adc. So
> I assume its use is not limited to voltage monitoring, and that you
> would in fact expect to change the gain during runtime (ie not only at
> system startup). Is this a correct assumption ?

This is the problem with having ADC drivers in drivers/hwmon. These are
versatile devices, they can be used for voltage monitoring but also for
a variety of other things, and the desired interface depends on that.
Runtime gain changes is not desirable at all for a voltage monitoring
device.

A solution to this may be to move the ADC driver itself somewhere else,
and have a dummy driver in hwmon/ merely adding a hwmon-style interface
on top of the main driver. Other such dummy driver could be written for
other use cases of the ADC. I think this is what the s3c-hwmon driver
is doing, and maybe others.

-- 
Jean Delvare




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