[Gta04-owner] bq27x00 driver for Replicant

Dr. H. Nikolaus Schaller hns at goldelico.com
Thu Mar 27 19:16:17 CET 2014


Am 27.03.2014 um 19:07 schrieb Dr. H. Nikolaus Schaller:

> Hi,
> 
> Am 27.03.2014 um 18:14 schrieb Alexandre Roumiantsev:
> 
>> Hello
>> 
>>> 
>>> But I wonder why you are doing this? 
>>> 
>>> There appear to be two changes:
>>> 
>>> a) reducing the default poll interval by factor 6
>>> 
>>> And, the battery poll interval can be set from user space when modprobing the module.
>>> Simply give the module a parameter "poll_interval=60" but leave the kernel driver as it is.
>> 
>> I agree that it possible to do as module parameter.
> 
> That is the way it should be done. Otherwise it will boomerang back to us as soon as we
> want to get something upstream.

Maybe the basic rule to follow here is: "never touch the kernel code if it provides an API to do the same adjustments from user space"

> 
>> 
>>> b) you disable the caching mechanism (which checks for relevant bits) and always notify power_supply_changed()
>>> 
>>> I doubt this is acceptable because I don't see what this has to do with battery status in real time.
>>> If there is no change reported from the battery there is no change to be reported to user space...
>>> 
>>> So if you are missing updates, there might be something wrong with the bits reported by the bq27000
>>> and that should be fixed.
>> 
>> I think so, but I repeat that battery technical detail is new for me and I would like that
>> somebody, who knows technical well give explanation.
> 
> I assume that the battery driver has gone through a lot of reviews since it is part of the
> official kernel.org tree. Therefore it must be quite correct and has not been changed recently.
> 
> We can also look into the data sheet to better understand how it works.
> 
> BTW: git blame drivers//power/bq27x00_battery.c
> 
> tells that Neil Brown has added this caching. I hope he is still reading this list
> and can comment.
> 
>> I only can tell, that according my testing only both changes together give a result
>> ( could see battery status in real time ).
> 
> I don't doubt that it solves the problem.
> 
> The question is if it is the right way to solve it or if it just interacts with some other bug
> in a positive way.
> 
> But I think now since we know that disabling the battery driver caching solves the
> problem it may help to understand why the user space is not getting regular updates
> without the patch.
> 
> BR,
> Nikolaus
> 
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