On Wed, Sep 23, 2015 at 05:02:28PM +0200, Sebastian Reichel wrote: > Hi, > > On Wed, Sep 23, 2015 at 09:11:46AM -0500, Andreas Dannenberg wrote: > > Ok. So how should we best go about extending the usage of the > > 'input_current_limit' sysfs node for this charger? You mentioned > > writing 'auto' into it should enable the auto-detection mode. I suppose > > writing a fixed current value will disable it. But how to indicate to > > the user when reading 'input_current_limit' whether auto mode is enabled > > or not (I think this is something we should do). > > Right, I haven't thought of this. > > > Can we return a mixed number/string like this? > > > > # Example: charger auto detection mode is disabled, and input current > > # limit is configured as 500mA. > > > > $ cat input_current_limit > > 500000 > > > > # Example: charger auto detection mode is enabled, and a charger > > # supporting 1A was detected (note the mixed number/string thats > > # returned) > > > > $ cat input_current_limit > > 1000000 (auto) > > > > Would that work? > > No. sysfs nodes should only contain one value per file. > > > Or should we introduce a new sysfs property? > > So maybe keep this patch as is (disallow setting the limit in auto > mode) and create another file for setting (and getting) the mode. Thanks for the continued feedback. Will look into this and add a new property. > Also it might be a good idea to return to safe defaults when the > charger is disconnected (-> reset to DT specified values). It already does this when the charger type auto-detection is enabled. When configured for manually setting the input current limit the use case is a bit more complex and I do not recommend resetting the limit to 500mA. Let me explain why: 1) Using USB chargers is only one of the ways the bq2525x devices can be used in a system. Imagine a shipping product that comes with its own proprietary wall power (or built-in) supply that let's say cranks out 2A. As a vendor you want to configure your system (meaning, the bq2425x via DT) to a fixed value of 2A. The user un-plugging and re-plugging the power supply should not arbitrarily change that pre-configured limit 2) Even in case of USB chargers, userspace could detect the power un-plug event, and re-configure the limit to something else. So I think it's really policy that should not be implemented in the Kernel driver. Regards, -- Andreas Dannenberg Texas Instruments Inc -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
