Re: [PATCH 01/15] mfd: add new driver for Sharp LoCoMo

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Fri, Oct 31, 2014 at 10:54 AM, Dmitry Eremin-Solenikov
<dbaryshkov@xxxxxxxxx> wrote:
> 2014-10-31 10:42 GMT+03:00 Linus Walleij <linus.walleij@xxxxxxxxxx>:

>> It seems some DAC handling is part of the MFD driver, and we recently
>> discussed that MFD should not be doing misc stuff but mainly act as
>> arbiter and switching station.
>>
>> Can you please move the DAC parts of the driver to
>> drivers/iio/dac?
>>
>> The IIO DAC subsystem will likely add other goodies to
>> the driver for free and give a nice API to consumers.
>
> I wanted this part to be as simple as possible. I will look into IIO
> DAC subsystem.
> The DAC is as simple 2 channel 8-bit i2c device connected to a separate i2c bus
> controlled through a register in LoCoMo device. One channel is used
> for backlight,
> other will be used for volume control. So (in theory) I can add the
> following device
> chain:  locomo -> i2c-locomo -> m62332 -> IIO DAC client.  However isn't that
> quite an overkill for just backlight & volume control? Please advice me on this.

The point is still the same: no unrelated code in drivers/mfd,
then either use IIO DAC as a middle layer or sink the DAC handling
into respective subdriver, i.e. push it into the backlight or
volume directly then.

>>> +       /* Longtime timer */
>>> +       writew(0, lchip->base + LOCOMO_LTINT);
>>> +       /* SPI */
>>> +       writew(0, lchip->base + LOCOMO_SPI + LOCOMO_SPIIE);
>>> +
>>> +       writew(6 + 8 + 320 + 30 - 10, lchip->base + LOCOMO_ASD);
>>
>> That's a few magic numbers and calculation don't you think?
>>
>> A comment stating what's going on would be helpful.
>
> Unfortunately little is known here - these values are c&p from old 2.4
> Lineo code.
> This part is related to generating synchronization pulses for accessing
> touchscreen.

OK we have to live with reverse engineering results, that's OK.

Yours,
Linus Walleij
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