Re: [PATCH] iio: Add support for LTC26xx I2C DAC

[Marc Andre <marc.andre@netline.ch>]

On 12.10.2015 12:26, Lars-Peter Clausen wrote:
> On 10/12/2015 10:52 AM, Marc Andre wrote:
>> This driver adds support for the Linear LTC26x6, LTC26x7 and LTC26x9 I2C
>> DAC chips.
> Those look like they are very much register map compatible to what is
> supported by the AD5064 driver.	It makes sense to add support for them there
> instead of having a separate driver.
I see that the interfaces are similar. Not all features of the ADxxxx 
are supported by the LTC26XX. e.g. it doesn't support the different 
power down modes. It also doesn't support the configuration register.
Other features available to AD which are not available to the LTC are 
LDAC by software, RESET and CLEAR commands. Those commands are currently 
not in use by the driver, but in the future, if those commands are used, 
a separation would have to be done to avoid issues with the LTC.

I first also thought that the address / command location is different as 
the AD5064 sends 4 bytes and "AD5064_ADDR(x)" is "((x) << 20)". By 
further reviewing I see that this only applies to SPI connected devices, 
while I2C connected devices have 3 bytes as LTC26xx.

I am quite open. I have the tendency to suggest a separate ltc26xx 
driver, also because it would allow simpler identification of the driver 
and separate evolution. (Someone would need to know that AD4064 is 
compatible to LTC26xx) I also think large drivers containing many 
separations between similar, but not equal devices are more risky to 
break on changes. No one has all those devices available for test. But I 
am a new contributor to the Kernel, thus I am interested to listen to 
the experts... :-)

Marc