linux-kernel - Re: [rtc-linux] [PATCH 8/8] ARM: vt8500: gpio: Devicetree support for arch-vt8500

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Date:	Wed, 8 Aug 2012 11:11:45 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	vt8500-wm8505-linux-kernel@...glegroups.com,
	Tony Prisk <linux@...sktech.co.nz>
Cc:	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Alan Cox <alan@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Hauke Mehrtens <hauke@...ke-m.de>, Felipe Balbi <balbi@...com>,
	Neil Zhang <zhangwm@...vell.com>,
	Florian Tobias Schandinat <FlorianSchandinat@....de>,
	Rob Landley <rob@...dley.net>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Stephen Warren <swarren@...dia.com>,
	Eric Andersson <eric.andersson@...xphere.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-fbdev@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-serial@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org
Subject: Re: [rtc-linux] [PATCH 8/8] ARM: vt8500: gpio: Devicetree support for arch-vt8500

On Wed, Aug 8, 2012 at 3:39 AM, Tony Prisk <linux@...sktech.co.nz> wrote:

> Converted the existing arch-vt8500 gpio to a platform_device.
> Added support for WM8505 and WM8650 GPIO controllers.
(...)
> +++ b/drivers/gpio/gpio-vt8500.c

This driver looks very one-bit-per-gpio typed. Are you sure you cannot
just reuse drivers/gpio/gpio-generic.c? Make a compelling case please...

> +struct vt8500_gpio_bank_regs {
> +       int     en;
> +       int     dir;
> +       int     data_out;
> +       int     data_in;

Why are all these members int? They should be u8 from reading your code.

> +       int     ngpio;
> +};


> +static struct vt8500_gpio_data vt8500_data = {
> +       .num_banks      = 7,
> +       .banks  = {
> +               VT8500_BANK(0x00, 0x20, 0x40, 0x60, 26),
> +               VT8500_BANK(0x04, 0x24, 0x44, 0x64, 28),
> +               VT8500_BANK(0x08, 0x28, 0x48, 0x68, 31),
> +               VT8500_BANK(0x0C, 0x2C, 0x4C, 0x6C, 19),
> +               VT8500_BANK(0x10, 0x30, 0x50, 0x70, 19),
> +               VT8500_BANK(0x14, 0x34, 0x54, 0x74, 23),
> +               VT8500_BANK(-1, 0x3C, 0x5C, 0x7C, 9),    /* external gpio */

What on earth are all those magic numbers?

I *guess* they're enabling some default GPIO settings etc.

But it really needs better structure, #defines for each one or
atleast include <linux/bitops.h> and say:

= BIT(4) | /* Enable GPIO pin 5 on this bank */
   BIT(5); /* Enable GPIO pin 6 on this bank */

However I suspect this is board specific and should
be taken from device tree. Please elaborate on this...

Ditto for the different instances.

(...)
> +       unsigned val;

Looks like all of these should be u8.

> +       val = readl(vt8500_chip->base + vt8500_chip->regs->en +
> +                                                       vt8500_chip->regoff);

val = (u8) readl(...);

usw

> +       val |= (1 << offset);

Use <linux/bitops.h>

val |= BIT(offset);

Apart from these remarks it's looking good...

Yours,
Linus Walleij
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