linux-kernel - Re: [PATCH] gpio: add a driver for GPIO pins found on AMD-8111 south bridge chips

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Date:	Fri, 27 Apr 2012 12:52:19 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpio: add a driver for GPIO pins found on AMD-8111 south
 bridge chips

On Fri, Apr 27, 2012 at 12:08 PM, Dmitry Eremin-Solenikov
<dbaryshkov@...il.com> wrote:

> Add a driver to use GPIO pins available on several AMD south bridges
> (currently only AMD 8111 is supported).
>
> Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@...il.com>

Mainly nitpicks, it's looking good overall...

> +       spin_lock_irqsave(&agp->lock, flags);
> +       temp = ioread8(agp->pm - PMBASE_OFFSET + PMBASE_GPIO(offset));
> +       temp = (temp & 0x1c) | (!!value);

This is a bit idomatic but I think I understand what's going on. However this
0x1C magic could be better of with some #define AMD_8111_GPIO_FOO don't
you think?

> +static int amd_gpio_get(struct gpio_chip *chip, unsigned offset)
> +{
> +       struct amd_gpio *agp = to_agp(chip);
> +       u8 temp;
> +
> +       temp = ioread8(agp->pm - PMBASE_OFFSET + PMBASE_GPIO(offset));
> +
> +       dev_dbg(&agp->pdev->dev, "Getting gpio %d, reg=%02x\n", offset, temp);
> +
> +       return !!(temp & 0x20);

And this could be #define AMD_8111_GPIO_INVAL or so (I bet this bit has a
name in the datasheet, right?)

> +static int amd_gpio_dirout(struct gpio_chip *chip, unsigned offset, int value)
> +{
> +       struct amd_gpio *agp = to_agp(chip);
> +       u8 temp;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&agp->lock, flags);
> +       temp = ioread8(agp->pm - PMBASE_OFFSET + PMBASE_GPIO(offset));
> +       temp = (temp & 0x10) | 0x4 | (!!value);

And so on...

> +       iowrite8(temp, agp->pm - PMBASE_OFFSET + PMBASE_GPIO(offset));
> +       spin_unlock_irqrestore(&agp->lock, flags);
> +
> +       dev_dbg(&agp->pdev->dev, "Dirout gpio %d, value %d, reg=%02x\n", offset, !!value, temp);
> +
> +       return 0;
> +}

> +static int __init mod_init(void)

amd_gpio_init() maybe? These names are nice for e.g. ftrace.

> +       printk(KERN_INFO "AMD-8111 GPIO detected\n");

pr_info() & friends are nice shorthands for this.

> +static void __exit mod_exit(void)

amd_gpio_mod_exit()?

> +MODULE_AUTHOR("The Linux Kernel team");

Don't be shy, put in your own name :-)

Yours,
Linus Walleij
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