linux-kernel - Re: [PATCH 3/4] mfd: 88pm800: add device tree support

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Date:	Thu, 15 Aug 2013 11:07:19 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Chao Xie <xiechao.mail@...il.com>
Cc:	Chao Xie <chao.xie@...vell.com>, sameo@...ux.intel.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] mfd: 88pm800: add device tree support

> >> +Optional parent device properties:
> >> +- marvell,88pm800-irq-write-clear: inicates whether interrupt status is cleared by write
> >> +- marvell,88pm800-battery-detection: indicats whether need 88pm800 to support battery
> >> +                             detection or not.
> >
> > Not sure what these are. This is why you need to CC the Device Tree
> > guys.
> >
> It is the 88pm805's own configuration.
> 88pm800-irq-write-clear: when irq happens, the status register is
> write clear or read clear.
> 88pm800-battery-detection: whether the battery is connected to chip.
> It means that whether
> the chip be aware of battery or not.

As you are adding vendor specific bindings, you need to Cc the Device
Tree mailing list.

> >> +     if (IS_ENABLED(CONFIG_OF)) {
> >> +             if (!pdata) {
> >> +                     pdata = devm_kzalloc(&client->dev,
> >> +                                          sizeof(*pdata), GFP_KERNEL);
> >> +                     if (!pdata)
> >> +                             return -ENOMEM;
> >> +             }
> >> +             ret = pm800_dt_init(node, &client->dev, pdata);
> >> +             if (ret)
> >> +                     return ret;
> >> +     } else if (!pdata) {
> >> +             return -EINVAL;
> >> +     }
> >
> > Replace with:
> >
> >         if (!pdata) {
> >                 if (node)
> >                         /* <blah> populate pdata with DT </blah> */
> >                 else
> >                         return -EINVAL;
> >         }
> >
> The orignial code will cover the following situation.
> 1. DT enabled, and user pass pdata
> 2. DT enabled, but user do not pass pdata
> 3. DT disabled, user pass pdata
> 4. DT disabled, user do not pass pdata.
> 
> 88pm805 has a callback for config the it based on platform requirment.
> I do not want to remove this callback now, because it includes so many
> configurations.
> So i allow user can pass pdata with callback if the platform needs to
> configure the chip.

Mixing DT with pdata is a bad idea. If you need to pass a call-back
pointer, then _only_ use pdata i.e. get all of your platform specific
information from pdata, rather than just over-writing sections of it
with information retrieved from Device Tree.

So:

If pdata  - use pdata and ignore DT completely
If !pdata:
   If DT  - use DT
   If !DT - return -EINVAL

Out of interest, what does your call-back do?

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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