On Fri, Aug 29, 2014 at 11:40:02AM +0100, ext Mark Rutland wrote: > On Fri, Aug 29, 2014 at 08:34:25AM +0100, Matti Vaittinen wrote: > > On Thu, Aug 28, 2014 at 10:40:34AM -0700, ext Guenter Roeck wrote: > > > On Thu, Aug 28, 2014 at 01:28:42PM -0400, Jason Cooper wrote: > > > > On Thu, Aug 28, 2014 at 09:48:25AM -0700, Guenter Roeck wrote: > > > > > > > > It may be a bit of overkill, but I think a DT macro would be the most > > > > maintainable solution here: > > > > > > > > #define DS1339_TRCKL_DIODE 0x08 > > > > #define DS1339_TRCKL_NODIODE 0x04 > > > > #define DS1339_TRCKL_R250 0x01 > > > > #define DS1339_TRCKL_R2000 0x02 > > > > #define DS1339_TRCKL_R4000 0x03 > > > > > > > > trickle_setup = <DS1339_TRCKL_DIODE | DS1339_TRCKL_R250>; > > > > > > > > And the driver would take care of oring it with the enable pattern. > > > > > > > > > > Yes, that sounds reasonable as well. > > > > > I thought of this too. However the ds1307 seems to be designed to work > > with bunch of chips. What then when next chip supported by this driver > > introduces 75, 1000 and 5000 ohm resistors? Or something else. (Or add > > some other configuration). I do not see this approach to be > > maintainable in long run. > > If a new chip comes out with new features, the driver will need an > update anyhow. We have no guarantee that the register placement will be > the same, let alone the layout. This is why I originally also added the trickle_reg property. But let's leave it out. > > If and when said new chip comes out we allocate a new compatible string. > If it's compatible iwith (i.e. is a superset of) an existing device's > programming model, we add that existing string as a fallback in the > compatible list so old kernels can drive the subset of features they > understand. Yes. > > > I see strong possibility of polluting dt with endless amount of > > defines. Furthermore I believe the benefits of these defines would be > > negligible compared to effort maintaining defines and documentation of > > them causes. Surely the one who needs to add dt node for this chip in > > his board's dt has the manual for the chip he has on board. Especially > > so if he knows the trickle charger there and wants to configure it. > > The plain resistor type still gives zero information without knowing > > the other details. > > I would rather that the driver had some idea of what it were doing > rather than being a glorified copy routine. > > I would suggest we have two properties that describe the resistor's > rating and whether or not there is a diode: > > trickle-resistor-ohms = <250> > diode-connected; > > That's easy for a human to write and/or validate, we can easily extend > it in future, requires no proliferation of macros, and describes the > hardware rather than telling software what to do. > > The driver becomes a little more complicated, but gains sanity checking, > which is a good thing. This looks like a nice way. Problem is that I can not provide support for all chips ds1307 supports. I have access to ds1339 variant only. I assume the driver should thus reject this dt information for all other chips for now. > > I'm still worried that we have no idea what the device is intended to > charge. Surely that's important? In my case it will charge capcitor which provides Vbackup for short power breaks. Br. --Matti Vaittinen -- ============================================= Matti Vaittinen Senile SW Specialist FINLAND ~~ When things go utterly wrong vim users can always type :help! ~~ -- 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
