On Tue, Oct 30, 2018 at 07:34:11PM +0000, Trent Piepho wrote: > On Tue, 2018-10-30 at 18:00 +0100, Marco Felsch wrote: > > On 18-10-30 06:13, Guenter Roeck wrote: > > > On 10/30/18 3:47 AM, Marco Felsch wrote: > > > > > > hwmon-gpio-simple sounds ok for me. > > > > > The most difficult part of such a driver would probably be to define acceptable > > > devicetree properties. > > > > That's true! One possible solution could be: > > > > hwmon_dev { > > compatible = "hwmon-gpio-simple"; > > name = "gpio-generic-hwmon"; > > update-interval-ms = 100; > > > > hwmon-gpio-simple,dev@0 { > > reg = <0>; > > gpio = <gpio3 15 GPIO_ACTIVE_LOW>; > > hwmon-gpio-simple,type = "in"; > > hwmon-gpio-simple,report = "crit_alarm"; > > }; > > > > hwmon-gpio-simple,dev@1 { > > reg = <1>; > > gpio = <gpio3 19 GPIO_ACTIVE_LOW>; > > hwmon-gpio-simple,type = "temp"; > > hwmon-gpio-simple,report = "alarm"; > > }; > > }; > > Here's some options: > > hwmon_dev { > /* Orthogonal to existing "gpio-fan" binding. */ > compatible = "gpio-alarm"; > /* Standard DT property for GPIO users is [<name>-]gpios */ > alarm-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>, > <&gpio3 19 GPIO_ACTIVE_LOW>; > /* A <prop>-names property is also a DT standard */ > alarm-gpios-names = "in0", "temp0"; temp1, and it would have to specify which alarm, but, yes, that would be better. > }; > > The driver can create hwmon alarm attribute(s) based on the name(s). I > used "alarm" as it seemed to fit the pattern established by the "fan" > driver. Both the gpio-fan and gpio-alarm driver use gpios, but I think > considering them one driver for that reason does not make sense. > > The names are very Linuxy, something that is not liked in DT bindings. > It also doesn't extend well if you need to add more attributes to each > alarm. Here's something that's more like what I did for the gpio-leds > binding. > > hwmon_dev { > compatible = "gpio-alarm"; > voltage@0 { > label = "Battery Voltage Low"; > type = "voltage"; > alarm-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>; > }; > cputemp@0 { > label = "CPU Temperature Critical"; > type = "temperature"; > interrupt-parent = <&gpio3>; > interrupts = <19 IRQ_TYPE_LEVEL_LOW>; > }; Even better, though the type of alarm (generic, min, max, lcrit, crit, cap, emergency, fault) is still needed. That needs to be specified by some explicit means, not with a label (though having a label is ok). There could also be more than one alarm per sensor (eg in0_lcrit_alarm, in0_min_alarm, in0_max_alarm, in0_crit_alarm), all of which would share a single label. Something like #define GPIO_ALARM_GENERIC 0 #define GPIO_ALARM_MIN 1 ... voltage@0 { label = "Battery Voltage"; type = "voltage"; alarm-type = <GPIO_ALARM_LCRIT, GPIO_ALARM_CRIT>; alarm-gpios = <&gpio3 15 GPIO_ACTIVE_LOW &gpio3 16 GPIO_ACTIVE_LOW>; }; with some better (acceptable) values for "alarm-type" and the actual fields. Guenter > }; > > Supporting interrupts instead of just a gpio would allow for edge > triggering. > > I can also see that someone might want to create some kind of time > based hysteresis for circuits that don't have that. While it would be > very easy to add a "linux,debounce = <1000>;" property, I imagine that > would be rejected as configuration in the DT binding.