linux-kernel - Re: [PATCH] regulator: axp20x: Get rid of AXP20X_xxx

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Date:   Thu, 21 Feb 2019 08:22:53 +0800
From:   Axel Lin <axel.lin@...ics.com>
To:     Olliver Schinagl <oliver@...inagl.nl>
Cc:     Mark Brown <broonie@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Priit Laes <plaes@...es.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regulator: axp20x: Get rid of AXP20X_xxx_START/END/STEPS defines

Olliver Schinagl <oliver@...inagl.nl> 於 2019年2月21日 週四 上午6:57寫道：
>
> Hey Axel,
>
> On February 20, 2019 5:50:13 PM GMT+01:00, Axel Lin <axel.lin@...ics.com> wrote:
> >The AXP20X_xxx_START/END/STEPS defines make the code hard to read and
> >very hard to check the linear range settings because it needs to check
> >the defines one-by-one.
> >The original code without the defines is very good in readability
> >as the meaning of each field of REGULATOR_LINEAR_RANGE is clear.
> >So I suggest to get rid of AXP20X_xxx_START/END/STEPS defines.
> Are you suggesting that magic values and hex numbers are more readable?

For example:
static const struct regulator_linear_range axp803_dcdc234_ranges[] = {
       REGULATOR_LINEAR_RANGE(500000, 0x0, 0x46, 10000),
       REGULATOR_LINEAR_RANGE(1220000, 0x47, 0x4b, 20000),
};
Above looks very clear to me as it describes the linear ranges:
1st linear range: min_uV is 500000, from selector 0 ~ 0x46, the uV_step is 10000
2nd linear range: min_uV is 1220000, from selector 0x47 ~ 0x4b, the
uV_step is 20000
And it's easy to check the min_sel and max_sel in each linear range.

Now, take a look at below code:
static const struct regulator_linear_range axp803_dcdc234_ranges[] = {
       REGULATOR_LINEAR_RANGE(500000,
                              AXP803_DCDC234_500mV_START,
                              AXP803_DCDC234_500mV_END,
                              10000),
       REGULATOR_LINEAR_RANGE(1220000,
                              AXP803_DCDC234_1220mV_START,
                              AXP803_DCDC234_1220mV_END,
                              20000),
};
1st linear range:
I have to check what is AXP803_DCDC234_500mV_START for min_sel,
then check what is AXP803_DCDC234_500mV_END for max_sel,
and AXP803_DCDC234_500mV_END is AXP803_DCDC234_500mV_START +
AXP803_DCDC234_500mV_STEPS
so I have to check if AXP803_DCDC234_500mV_STEPS is correct or not.
The same for 2nd linear range.
It's unnecessary complexity.
And it's just for 2 linear ranges, for axp20x_ldo4_ranges with 5 linear range,
it's really hard to check the settings.

IMHO, In such case, the defines does not help.
It's a rare case that I suggest to remove the defines.

>
> Maybe you can explain what your problem is, as it appears you are trying to debug something?
well, I just read the code.
I just found it's very hard to read the linear range setting for this driver.

Regards,
Axel