Hello, On Wed, Sep 26, 2018 at 12:58:17PM -0700, Guenter Roeck wrote: > On Wed, Sep 26, 2018 at 11:02:44AM -0700, Nicolin Chen wrote: > > On Wed, Sep 26, 2018 at 06:06:32AM -0700, Guenter Roeck wrote: > > > On 09/25/2018 11:42 PM, Nicolin Chen wrote: > > > > The inX_enable interface allows user space to enable or disable > > > > the corresponding channel. Meanwhile, according to hwmon ABI, a > > > > disabled channel/sensor should return -ENODATA as a read result. > > > > > > > > However, there're configurable nodes sharing the same __show() > > > > functions. So this change also adds to check if the attribute is > > > > read-only to make sure it's not reading a configuration but the > > > > sensor data. > > > > > One necessary high level change I don't see below: With this change, > > > we should no longer drop a channel entirely if it is disabled from > > > devicetree. All channels should be visible but report -ENODATA if > > > disabled. In other words, it should be possible for the 'enable' flag > > > to override settings in DT. > > > > Hmm...I don't feel so convinced here. The status in DT binding isn't > > exactly a setting but a physical status: if a hardware design leaves > > a channel to be disconnected, I don't really see a point in enabling > > it in the runtime. Or maybe you can shed some light on it? > > > > You are making an assumption from your use case. It might as well be that > some or all channels are disabled in DT by default to conserve power, > not because they are disconnected. I think I probably should update my DT binding somehow to say it explicitly that the property should be only used in cases of the physical disconnections, although I feel the current binding "no input source" already has the same meaning. In my opinion, disabling channels in DT to save power isn't very plausible, because it sounds more likely a user decision, while, as we know, DT merely describes the hardware design. Otherwise, if we want something like a setting for this purpose, we should probably use a different property for DT binding, bool type "disable-on-boot" for example. > > Meanwhile, I believe the enable nodes are necessary in either way as > > users could decide to disable the connected channels, based on their > > use cases, to save power. > > > Agreed, though I would not say "necessary". "Useful" seems to be more > appropriate. Yea..
