On Fri, May 18, 2012 at 06:34:01PM +0100, Jonathan Cameron wrote: > On 05/18/2012 01:27 PM, Johan Hovold wrote: [...] > > I really think that this should remain a device specific attribute as I > > originally suggested. It's an integration parameter that needs to be set > > precisely depending on the actual hardware setup (which analog light > > sensor and other external components). > Then it shouldn't be exposed to userspace. If there is reason to vary > it from userspace then it is a calibration parameter and should be > treated like the other ones we have, if not it should be done from > dt or platform data. > > > > The lm3533 also supports two types of light sensors: pwm- and analog- > > output ones. The resistor select settings only applies when in analog > > mode as the input is always high impedance otherwise. Thus a generic > > attribute (such as calibscale or hardware gain) shouldn't be used as it > > will have no effect whatsoever in PWM-mode. > > > > I'm thus back at my original proposal, albeit with a different name (I > > think a lot of this discussion could have been avoided had I not > > misnamed the parameter "gain"): > > > > What: /sys/bus/iio/devices/iio:deviceX/r_select > > Description: > > Set the ALS internal pull-down resistor for analog input mode > > (1..127), such that, > > > > R_als = 200000 / r_select (ohm) > > > > This setting is ignored in PWM-mode (input is always high > > impedance in PWM-mode). > > > > I don't think much is gained from using ohm as the unit: it just adds > > complexity and the selected resistor setting will likely not match the > > input value anyway. It's better that the chip integrators have full > > control over which resistor setting is actually used so that it matches > > external components. > This smacks of something that should never be exposed to users. > I'd hide it away in platform data. Fair enough. I'll drop the sysfs param and submit a patch for mfd-next which adds r_select to the platform data. Thanks, Johan -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
