Hi, On Fri, Sep 11, 2015 at 09:58:40AM +0900, Krzysztof Kozlowski wrote: > On 11.09.2015 01:42, Andrew F. Davis wrote: > > On 09/09/2015 06:47 PM, Krzysztof Kozlowski wrote: > >>>>> +- ti,enable-user-write: boolean, if present driver will allow the > >>>>> user space > >>>>> + to control the charging current and voltage through sysfs; > >>>> > >>>> This is not DT property. It does not describe hardware. > >>> We needed a mechanism to enable the sysfs writes on certain properties. > >>> If DT is not the place where should it go? > >> > >> DT is not the place. As I discussed later with Andreas, if you really > >> need this and if mainline is a place for that then probably this should > >> be compile option (a Kconfig symbol). > >> > > > > I think this would actually be a good use for module parameters, this way > > it could still be set at boot without re-compiling. > > > > I think compile-time disabling sysfs properties because they are > > "dangerous" is > > a little bit too artificially restricting and controlling, you can set > > permissions > > so only root can change them already. The kernel should not be > > restricting root, > > I understand the fear of someone rooting a machine and remotely over > > charging > > a LiPo[1], but these physical limits are hardware descriptions and can > > and should > > be set by DT, beyond this root should have full control over their machine. > > > Indeed module parameters could be used for enabling/disabling debug > options... but as fair as I understand these are for purely development > purposes. That is why they got into DT initially, right? To allow the > developer to play with it on the development board? > > This is why I am really not convinced that this should go to mainline. > > Anyway if it goes, then maybe compiling it out is the safest choice? > What's the purpose of having it in kernel all the time? If this was a > debug option, than some experienced user could turn it on and report to > LKML with extended debug data. But it's not a debug but development option? Changing the current limit is useful for "expert" users with custom usb power supplies, that are not correctly detected by extcon. I also think a module parameter would be the best option here. -- Sebastian
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