linux-kernel - Re: [PATCH v2 5/5] gpio: pca953x: Add support for PCAL6534

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Message-ID: <Yxc8GgUnHOuMIn4p@smile.fi.intel.com>
Date:   Tue, 6 Sep 2022 15:24:58 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Martyn Welch <martyn.welch@...labora.co.uk>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Martyn Welch <martyn.welch@...labora.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] gpio: pca953x: Add support for PCAL6534

On Tue, Sep 06, 2022 at 09:28:19AM +0100, Martyn Welch wrote:
> From: Martyn Welch <martyn.welch@...labora.com>
> 
> Add support for the NXP PCAL6534. This device is broadly a 34-bit version
> of the PCAL6524. However, whilst the registers are broadly what you'd
> expect for a 34-bit version of the PCAL6524, the spacing of the registers
> has been compacted. This has the unfortunate effect of breaking the bit
> shift based mechanism that is employed to work out register locations used
> by the other chips supported by this driver. To accommodate ths, callback
> functions have been added to allow alterate implementations of
> pca953x_recalc_addr() and pca953x_check_register() for the PCAL6534.


This looks much cleaner!

...

> @@ -107,6 +109,7 @@ static const struct i2c_device_id pca953x_id[] = {
>  	{ "tca9539", 16 | PCA953X_TYPE | PCA_INT, },
>  	{ "tca9554", 8  | PCA953X_TYPE | PCA_INT, },
>  	{ "xra1202", 8  | PCA953X_TYPE },
> +
>  	{ }

Missed Diodes?

>  };
>  MODULE_DEVICE_TABLE(i2c, pca953x_id);

...

> +	u8 (*recalc_addr)(struct pca953x_chip *chip, int reg , int off);
> +	bool (*check_reg)(struct pca953x_chip *chip, unsigned int reg,
> +		          u32 checkbank);

I would think of splitting this change. Like in a separate patch you simply
create this interface and only add what you need in the next one.

...

> +static bool pcal6534_check_register(struct pca953x_chip *chip, unsigned int reg,
> +				    u32 checkbank)
> +{
> +	int bank;
> +	int offset;
> +
> +	if (reg > 0x2f) {

I guess code read and generation wise the

	if (reg >= 0x30) {

is slightly better.

> +		/*
> +		 * Reserved block between 14h and 2Fh does not align on
> +		 * expected bank boundaries like other devices.
> +		 */
> +		int temp = reg - 0x30;
> +
> +		bank = temp / NBANK(chip);
> +		offset = temp - (bank * NBANK(chip));

Parentheses are not needed fur multiplication, but if you insist...

> +		bank += 8;

> +	} else if (reg > 0x53) {

In the similar way...

> +		/* Handle lack of reserved registers after output port
> +		 * configuration register to form a bank.
> +		 */

Comment style

/*
 * Handle...
 */

> +		int temp = reg - 0x54;
> +
> +		bank = temp / NBANK(chip);
> +		offset = temp - (bank * NBANK(chip));
> +		bank += 16;
> +	} else {
> +		bank = reg / NBANK(chip);
> +		offset = reg - (bank * NBANK(chip));
> +	}
> +
> +	/* Register is not in the matching bank. */
> +	if (!(BIT(bank) & checkbank))
> +		return false;
> +
> +	/* Register is not within allowed range of bank. */
> +	if (offset >= NBANK(chip))
> +		return false;
> +
> +	return true;
> +}

...

> -	u8 regaddr = pinctrl | addr | (off / BANK_SZ);
>  
> -	return regaddr;
> +	return pinctrl | addr | (off / BANK_SZ);

Stray change, or anything I have missed?

...

> +/* The PCAL6534 and compatible chips have altered bank alignment that doesn't
> + * fit within the bit shifting scheme used for other devices.
> + */

Comment style.

...

> @@ -1240,6 +1335,7 @@ static const struct of_device_id pca953x_dt_ids[] = {
>  
>  	{ .compatible = "nxp,pcal6416", .data = OF_953X(16, PCA_LATCH_INT), },
>  	{ .compatible = "nxp,pcal6524", .data = OF_953X(24, PCA_LATCH_INT), },
> +	{ .compatible = "nxp,pcal6534", .data = OF_653X(34, PCA_LATCH_INT), },
>  	{ .compatible = "nxp,pcal9535", .data = OF_953X(16, PCA_LATCH_INT), },
>  	{ .compatible = "nxp,pcal9554b", .data = OF_953X( 8, PCA_LATCH_INT), },
>  	{ .compatible = "nxp,pcal9555a", .data = OF_953X(16, PCA_LATCH_INT), },

Do you decide to drop Diodes compatible from the code?

-- 
With Best Regards,
Andy Shevchenko