Re: [PATCH 4/9] ARM: SPMP8000: Add ADC driver

[Jonathan Cameron <jic23@cam.ac.uk>]

On 10/12/11 15:42, Mark Brown wrote:
> On Tue, Oct 11, 2011 at 05:24:47PM +0200, Arnd Bergmann wrote:
>> On Tuesday 11 October 2011, Mark Brown wrote:
> 
>>> I'm not sure that IIO isn't the kernel subsystem we're looking for here
>>> - as I keep saying when this comes up it's just representing bare DACs
>>> and ADCs pretty directly which looks like a generic subsystem to me.
> 
>> Possible, yes. Until now, IIO is a subsystem for user-level access
>> not for kernel access though, so it's not the right place yet.
>> If we decide to let IIO handle all ADC input, do you think it would
>> also be the right place to do PWM output, rather than having a
>> separate subsystem for that?
> 
> Off the top of my head I'd expect PWM to be a separate thing which could
> optionally synthesize stuff onto an IIO device (bitbanging the PWM
> essentially).  The specialized PWM stuff tends to be "output this steady
> state for an indefinite period" type interface rather than "here's a
> batch of samples, output them".
Same can be true of dds chips, with the addition that they often have
gpio type switching between a set of predefined frequencies (FM basically).
+ weird waveform choices sometimes.