linux-kernel - Re: [PATCH 3/3] i2c: nomadik: Add Device Tree support to the Nomadik I2C driver

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Message-ID: <CACRpkdZ=C1EV4WO2b=1YLHPNhsDsQdq7Kfnpzm8i7uGRtVjJuQ@mail.gmail.com>
Date:	Mon, 3 Sep 2012 11:22:28 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	Wolfram Sang <w.sang@...gutronix.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	STEricsson_nomadik_linux@...t.st.com, linus.walleij@...ricsson.com,
	arnd@...db.de, linux-i2c@...r.kernel.org
Subject: Re: [PATCH 3/3] i2c: nomadik: Add Device Tree support to the Nomadik
 I2C driver

On Fri, Aug 31, 2012 at 2:23 PM, Lee Jones <lee.jones@...aro.org> wrote:

(...)
>  static int nmk_i2c_probe(struct amba_device *adev, const struct amba_id *id)
>  {
>         int ret = 0;
>         struct nmk_i2c_controller *pdata = adev->dev.platform_data;
> +       struct device_node *np = adev->dev.of_node;
>         struct nmk_i2c_dev      *dev;
>         struct i2c_adapter *adap;
>
> +       if (np) {
> +               if (!pdata) {

So, if no pdata is provided, we go on to allocate some ...

> +                       pdata = devm_kzalloc(&adev->dev, sizeof(*pdata), GFP_KERNEL);
> +                       if (!pdata) {
> +                               ret = -ENOMEM;
> +                               goto err_no_mem;
> +                       }
> +               }
> +               /* Provide the default configuration as a base. */
> +               pdata = &u8500_i2c;

Then you just override that pointer with a pointer to the local config.

> +               nmk_i2c_of_probe(np, pdata);
> +       }
> +
>         if (!pdata)
>                 /* No i2c configuration found, using the default. */
>                 pdata = &u8500_i2c;

This in it's entirety does not look sound. I *think* this is what you
want to do,
replace all of the above codde (including the last if (!pdata) clause) with:

if (!pdata) {
    /* If no platform data passed in, use the default configuration as
a base. */
    pdata = &u8500_i2c;
    if (np)
        /* Further, if we have a DT node, override the default with this */
        nmk_i2c_of_probe(np, pdata);
}

This makes any passed pdata take precedence, else default pdata
complemented with DT info. Which is what we want.

Yours,
Linus Walleij
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