On Sat, Jun 06, 2015 at 03:10:09PM +0200, Pavel Machek wrote: > On Tue 2015-06-02 07:37:31, NeilBrown wrote: > > On Mon, 1 Jun 2015 19:06:52 +0530 Kishon Vijay Abraham I <kishon@xxxxxx> > > wrote: > > > > > Hi, > > > > > > On Thursday 16 April 2015 01:33 PM, NeilBrown wrote: > > > > From: NeilBrown <neilb@xxxxxxx> > > > > > > > > The twl4030 phy can measure, with low precision, the > > > > resistance-to-ground of the ID pin. > > > > > > > > Add a function to read the value, and export the result > > > > via sysfs. > > > > > > Little sceptical about adding new sysfs entries. Do you have a good reason to > > > add this? > > > > The hardware can report the value, so why not present it to user-space? > > > > I originally used this with a udev rule which would configure the maximum > > current based on the resistance measure - to work with the particular charger > > hardware I have. > > > > More recent patches try to do all of the max-current configuration in the > > kernel, so I could live without exporting the value via sysfs if that is a > > show-stopper. > > > > I can't see where the scepticism comes from though. It is a well defined > > and cleary documented feature of the hardware. Why not expose it? > > sysfs interface is supposed to work for different chargers, without userspace > noticing. > > Are these values the ones that are likely to be useful there? These values come from Battery Charger specification 1.1+, IIRC, so no other values should show up unless documented in future BC revisions. > > > > + Possible values are: > > > > + ground > > > > + 102k > > > > + 200k > > > > + 440k > > > > + floating > > > > + unknown > > ...or would it make more sense to export for example numerical ohms, as that's > what are other chargers likely to provide? How do you expose "floating" in Ohms ? UINT_MAX might be one way, but that would have to be documented. -- balbi
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