linux-kernel - Re: [PATCH v8] mfd: Add Cherry Trail Whiskey Cove PMIC driver

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Message-ID: <20170605074900.zyxl2noxddm7q3a3@dell>
Date:   Mon, 5 Jun 2017 08:49:00 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Bin Gao <bin.gao@...el.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>
Subject: Re: [PATCH v8] mfd: Add Cherry Trail Whiskey Cove PMIC driver

On Sun, 04 Jun 2017, Hans de Goede wrote:

> Hi,
> 
> On 30-05-17 15:05, Andy Shevchenko wrote:
> > On Tue, 2017-05-30 at 13:20 +0100, Lee Jones wrote:
> > > On Tue, 30 May 2017, Andy Shevchenko wrote:
> > > 
> > > > On Tue, May 30, 2017 at 12:02 PM, Lee Jones <lee.jones@...aro.org>
> > > > wrote:
> > > > > On Tue, 23 May 2017, Hans de Goede wrote:
> > > > > > +static const struct i2c_device_id cht_wc_i2c_id[] = {
> > > > > > +     { }
> > > > > > +};
> > > > > 
> > > > > What's the point in this empty table?
> > > > 
> > > > This is artifact of I2C framework, otherwise if will be not
> > > > enumerated.
> > > > 
> > > > +Wolfram.
> > > > 
> > > > Wolfram, can we fix this? (In case we have either ACPI table or OF
> > > > table there is no need to oblige providing empty legacy table)
> > > 
> > > I think I fixed this already.
> > > 
> > > Hint: `git grep probe_new -- drivers/i2c` >
> > Indeed.
> > Thanks for a hint!
> 
> Unfortunately switching to probe_new (which I've done for
> the upcoming v9 of the MFD CHT Whiskey Cove driver) is not enough,
> as i2c_device_probe() (from drivers/i2c/i2c-core) still has:
> 
>         /*
>          * An I2C ID table is not mandatory, if and only if, a suitable Device
>          * Tree match table entry is supplied for the probing device.
>          */
>         if (!driver->id_table &&
>             !i2c_of_match_device(dev->driver->of_match_table, client))
>                 return -ENODEV;
> 
> So before we can remove the empty id tables from various ACPI
> drivers we first need to extend this check to also work with
> ACPI device matching.

I remember writing some ACPI support (see: i2c_device_match()), but
you're right, it needs a more complete implementation.  None of the
devices I work(ed) on support ACPI, so it wasn't a requirement for me.
Perhaps you can extend the support.


-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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