Re: [PATCH] IIO: ADC: New driver for the AD7298 8-channel SPI ADC

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

On 02/22/11 21:13, Michael Hennerich wrote:
> On 02/22/2011 03:34 PM, Jonathan Cameron wrote:
>> On 02/14/11 14:03, michael.hennerich@analog.com wrote:
>>   
>>> From: Michael Hennerich <michael.hennerich@analog.com>
>>>
>>> This patch adds support for the
>>> AD7298:  8-Channel, 1MSPS, 12-Bit SAR ADC with Temperature Sensor
>>> via SPI bus.
>>>
>>> This patch replaces the existing ad7298.c driver completely.
>>> It was necessary since, the old driver did not comply with the
>>> IIO ABI for such devices.
>>>     
>> Guess that's one approach to fixing up a driver!
>> Anyhow, it's nice and clean now.
>>   
> Rewrite is sometimes easier than fix ;-)
> 
>> Couple of trivial points inline.  You may need some locking
>> in the temperature read function, fix that or explain what
>> I'm missing before sending on to Greg, the other bits are up
>> to you.
>>   
> Good point.
>> I see the original driver used a busy pin. For the record, could you
>> also explain any disadvantages in this new one not doing that?
>>   
> Well the busy pin is only used to for on-die temperature measurements.
> The busy time is pretty deterministic, wasting a GPIO or interrupt line
> is pointless!
> Sleep for at least 100us, does the job. I see no point what this task
> could do useful otherwise,
> since it would also result in a sleep.
> 
> Last but not least - this is a 8-Channel ADC, the temperature diode is
> only the hard wired 9th channel,
> with pretty limited use. The busy pin might be useful for none OS 8-bit
> micro systems, but here
> we simply put the task asleep.
Good, that gives us a clean explanation to refer people to if they ask
this question in the future.  Thanks for clearing that up.

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