Re: [PATCH 7/8] gpio: stmpe: Add STMPE1600 support

[Patrice Chotard <patrice.chotard@st.com>]

On 04/20/2016 04:53 PM, Linus Walleij wrote:
> On Tue, Apr 19, 2016 at 2:18 PM,  <patrice.chotard@st.com> wrote:
>
>> From: Patrice Chotard <patrice.chotard@st.com>
>>
>> The particularities of this variant are:
>> - GPIO_XXX_LSB and GPIO_XXX_MSB memory locations are inverted compared
>>    to other variants.
>> - There is no Edge detection, Rising Edge and Falling Edge registers.
>> - IRQ flags are cleared when read, no need to write in Status register.
>>
>> Signed-off-by: Amelie DELAUNAY <amelie.delaunay@st.com>
>> Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
>> -       u8 reg = stmpe->regs[STMPE_IDX_GPMR_LSB] - (offset / 8);
>> +       u8 reg;
>>          u8 mask = 1 << (offset % 8);
>>          int ret;
>>
>> +       if (stmpe->partnum == STMPE1600)
>> +               reg = stmpe->regs[STMPE_IDX_GPMR_LSB] + (offset / 8);
>> +       else
>> +               reg = stmpe->regs[STMPE_IDX_GPMR_LSB] - (offset / 8);
> This construct is a bit hard to grasp.
>
> Can we think of something more intuitive? Maybe using more
> code lines but easier to understand.
>
> Subtracting the offset is just totally unintuitive in the first place,
> the STMPE1600 arrangement is much more intuitive.
>
> I would prefer if we address the LSB+MSB register explicitly
> instead of adding or subtracting 1 to the LSB register to get
> to the MSB register.
>
>> +       if (stmpe->partnum == STMPE1600)
>> +               reg = stmpe->regs[which] + (offset / 8);
>> +       else
>> +               reg = stmpe->regs[which] - (offset / 8);
> Same.
>
>> +       if (stmpe->partnum == STMPE1600)
>> +               reg = stmpe->regs[STMPE_IDX_GPDR_LSB] + (offset / 8);
>> +       else
>> +               reg = stmpe->regs[STMPE_IDX_GPDR_LSB] - (offset / 8);
> Same.
>
>> +       if (stmpe->partnum == STMPE1600)
>> +               reg = stmpe->regs[STMPE_IDX_GPDR_LSB] + (offset / 8);
>> +       else
>> +               reg = stmpe->regs[STMPE_IDX_GPDR_LSB] - (offset / 8);
> Same.
>
>> +                               stmpe_reg_write(stmpe,
>> +                                               stmpe->regs[regmap[i]] + j,
>> +                                               new);
>> +                       else
>> +                               stmpe_reg_write(stmpe,
>> +                                               stmpe->regs[regmap[i]] - j,
>> +                                               new);
> This is also unintuitively backwards.
>
>> +       if (stmpe->partnum == STMPE1600)
>> +               dir_reg = stmpe->regs[STMPE_IDX_GPDR_LSB] + (offset / 8);
>> +       else
>> +               dir_reg = stmpe->regs[STMPE_IDX_GPDR_LSB] - (offset / 8);
> Same.
>
>> +       if (stmpe->partnum == STMPE1600)
>> +               statmsbreg = stmpe->regs[STMPE_IDX_ISGPIOR_LSB];
>> +       else
>> +               statmsbreg = stmpe->regs[STMPE_IDX_ISGPIOR_MSB];
> And this kind of points at the problem.
>
> Can we write this in some way that make it super-clear which register
> we're using and why?

Ok i will rework all these points

Thanks

Patrice

>
> Yours,
> Linus Walleij