linux-kernel - Re: [PATCH] mfd: add bq2415x charger driver

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Message-ID: <CAMP44s1D8fbifOuuubMUbW=Z-DOF20B2dz+JR5ZPSqG-G3Ca-Q@mail.gmail.com>
Date:	Tue, 6 Dec 2011 15:50:56 +0200
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	Sebastian Reichel <sre@...ian.org>
Cc:	Felipe Contreras <felipe.contreras@...ia.com>,
	linux-main <linux-kernel@...r.kernel.org>,
	linux-omap <linux-omap@...r.kernel.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Pali Rohár <pali.rohar@...il.com>,
	Aliaksei Katovich <aliaksei.katovich@...ia.com>,
	Vladimir Zapolskiy <vz@...ia.com>
Subject: Re: [PATCH] mfd: add bq2415x charger driver

2011/12/6 Sebastian Reichel <sre@...ian.org>:
> On Tue, Dec 06, 2011 at 04:49:37AM +0200, Felipe Contreras wrote:
>> Not really. There are 6 bits: 640, 320, 160, 80, 40, 20. So values
>> from 0 to 1260mV can be represented, at steps of 20mV. A value of 0
>> means 3.5V.
>
> I just checked it. You'r driver just writes 0x42 to the register,
> which makes use of the described platform specific resistor.
>
>> bq2415x_i2c_write(cli, BQ2415X_CHG_CTL, 0x42);
>
> I know that 42 is the "Answer to the Ultimate Question of Life, the
> Universe, and Everything" [0]. But in this case 0x42 is platform
> specific. Check page 30 in the specs, From Table 9 onwards.

Well, you were talking about BQ2415X_VOLTAGE_SCALE, which I used for
the voltage register calculation.

But yeah, you are right about BQ2415X_CHG_CTL. Maybe it would make
sense to make it a platform driver, or perhaps just expose functions
so the board can set the right values.

>> > Apart from this I think those values should be exposed to sysfs
>> > via /sys/class/power_supply.
>>
>> Perhaps. Although I don't see much of the power supply interface that
>> could be useful here, but if so, I guess this should be indeed in
>> 'drivers/power'.
>
> So it may need some new entries. Normal mobile userspace wants to
> know at least charging status & speed. Also it's probably a good
> idea to make current_limit sysfs entry writeable, so that advanced
> users can overwrite a autodetected value (e.g. a dumb wallcharger
> may be detected as 100mA, but can provide 1A).

True. drivers/power it is then :)

-- 
Felipe Contreras
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