linux-kernel - Re: [PATCH v7 3/3] pinctrl: nuvoton: Add ma35d1 pinctrl and GPIO driver

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Date: Mon, 22 Apr 2024 12:10:39 +0800
From: Jacky Huang <ychuang570808@...il.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: linus.walleij@...aro.org, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 p.zabel@...gutronix.de, j.neuschaefer@....net,
 linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 ychuang3@...oton.com, schung@...oton.com
Subject: Re: [PATCH v7 3/3] pinctrl: nuvoton: Add ma35d1 pinctrl and GPIO
 driver

Dear Andy,

On 2024/4/10 下午 04:54, Andy Shevchenko wrote:
>> +#define MA35_GP_MODE_MASK_WIDTH              2
>> +
>> +#define MA35_GP_SLEWCTL_MASK_WIDTH   2
> I looked at the code how you use these... Oh, please switch to FIELD_GET() /
> FIELD_PREP() (don't forget to include bitfield.h)
>
> ...
>
> ...
>> +             regval &= ~GENMASK(setting->shift + MA35_MFP_BITS_PER_PORT - 1,
>> +                                setting->shift);
> This will generate an awful code. Use respective FIELD_*() macros.
>
> ...
>
>> +     regval &= ~GENMASK(gpio * MA35_GP_MODE_MASK_WIDTH - 1,
>> +                        gpio * MA35_GP_MODE_MASK_WIDTH);
>> +     regval |= mode << gpio * MA35_GP_MODE_MASK_WIDTH;
> Ditto.
>
> ...
>
>> +     regval &= GENMASK(gpio * MA35_GP_MODE_MASK_WIDTH - 1,
>> +                       gpio * MA35_GP_MODE_MASK_WIDTH);
>> +
>> +     return regval >> gpio * MA35_GP_MODE_MASK_WIDTH;
> Ditto.
>
> ...
>
>

Allow me to remove irrelevant parts.

I attempted to follow your advice and use FIELD_GET() and FIELD_PREP(), 
but found
it impractical. The reason is that these two macros require their 'mask' 
argument
to be a constant, otherwise compilation errors occur, which is the issue 
I encountered.
Since the mask here is calculated and not a constant, compilation errors 
occur.

Taking MA35_GP_REG_MODE as an example, within 32 bits, every 2 bits 
represent
the mode of a GPIO pin, and the mask is obtained by GENMASK(gpio * 2 -1, 
gpio * 2),
where the 'gpio' argument is a variable, not a constant, leading to 
compilation
errors.

Due to this reason, I will leave this part unchanged, or do you have any 
other suggestions?

Best Regards,
Jacky Huang