Re: [PATCH v2 1/4] mfd: Kontron PLD mfd driver

[Samuel Ortiz <sameo@linux.intel.com>]

Hi Linus,

On Wed, Jun 19, 2013 at 10:40:04AM +0200, Linus Walleij wrote:
> On Tue, Jun 18, 2013 at 11:04 PM, Kevin Strasser
> <kevin.strasser@linux.intel.com> wrote:
> > Add core MFD driver for the on-board PLD found on some Kontron embedded
> > modules. The PLD device may provide functions like watchdog, GPIO, UART
> > and I2C bus.
> >
> > The following modules are supported:
> >         * COMe-bIP#
> >         * COMe-bPC2 (ETXexpress-PC)
> >         * COMe-bSC# (ETXexpress-SC T#)
> >         * COMe-cCT6
> >         * COMe-cDC2 (microETXexpress-DC)
> >         * COMe-cPC2 (microETXexpress-PC)
> >         * COMe-mCT10
> >         * ETX-OH
> >
> > Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
> > Signed-off-by: Michael Brunner <michael.brunner@kontron.com>
> > Acked-by: Guenter Roeck <linux@roeck-us.net>
> > Acked-by: Darren Hart <dvhart@linux.intel.com>
> 
> (...)
> > +/**
> > + * kempld_read8 - read 8 bit register
> > + * @pld: kempld_device_data structure describing the PLD
> > + * @index: register index on the chip
> > + *
> > + * kempld_get_mutex must be called prior to calling this function.
> > + */
> > +u8 kempld_read8(struct kempld_device_data *pld, u8 index)
> > +{
> > +       iowrite8(index, pld->io_index);
> > +       return ioread8(pld->io_data);
> > +}
> > +EXPORT_SYMBOL_GPL(kempld_read8);
> > +
> > +/**
> > + * kempld_write8 - write 8 bit register
> > + * @pld: kempld_device_data structure describing the PLD
> > + * @index: register index on the chip
> > + * @data: new register value
> > + *
> > + * kempld_get_mutex must be called prior to calling this function.
> > + */
> > +void kempld_write8(struct kempld_device_data *pld, u8 index, u8 data)
> > +{
> > +       iowrite8(index, pld->io_index);
> > +       iowrite8(data, pld->io_data);
> > +}
> > +EXPORT_SYMBOL_GPL(kempld_write8);
> > +
> > +/**
> > + * kempld_read16 - read 16 bit register
> > + * @pld: kempld_device_data structure describing the PLD
> > + * @index: register index on the chip
> > + *
> > + * kempld_get_mutex must be called prior to calling this function.
> > + */
> > +u16 kempld_read16(struct kempld_device_data *pld, u8 index)
> > +{
> > +       return kempld_read8(pld, index) | kempld_read8(pld, index + 1) << 8;
> > +}
> > +EXPORT_SYMBOL_GPL(kempld_read16);
> > +
> > +/**
> > + * kempld_write16 - write 16 bit register
> > + * @pld: kempld_device_data structure describing the PLD
> > + * @index: register index on the chip
> > + * @data: new register value
> > + *
> > + * kempld_get_mutex must be called prior to calling this function.
> > + */
> > +void kempld_write16(struct kempld_device_data *pld, u8 index, u16 data)
> > +{
> > +       kempld_write8(pld, index, (u8)data);
> > +       kempld_write8(pld, index + 1, (u8)(data >> 8));
> > +}
> > +EXPORT_SYMBOL_GPL(kempld_write16);
> > +
> > +/**
> > + * kempld_read32 - read 32 bit register
> > + * @pld: kempld_device_data structure describing the PLD
> > + * @index: register index on the chip
> > + *
> > + * kempld_get_mutex must be called prior to calling this function.
> > + */
> > +u32 kempld_read32(struct kempld_device_data *pld, u8 index)
> > +{
> > +       return kempld_read16(pld, index) | kempld_read16(pld, index + 2) << 16;
> > +}
> > +EXPORT_SYMBOL_GPL(kempld_read32);
> > +
> > +/**
> > + * kempld_write32 - write 32 bit register
> > + * @pld: kempld_device_data structure describing the PLD
> > + * @index: register index on the chip
> > + * @data: new register value
> > + *
> > + * kempld_get_mutex must be called prior to calling this function.
> > + */
> > +void kempld_write32(struct kempld_device_data *pld, u8 index, u32 data)
> > +{
> > +       kempld_write16(pld, index, (u16)data);
> > +       kempld_write16(pld, index + 2, (u16)(data >> 16));
> > +}
> > +EXPORT_SYMBOL_GPL(kempld_write32);
> (...)
> > +extern u8 kempld_read8(struct kempld_device_data *pld, u8 index);
> > +extern void kempld_write8(struct kempld_device_data *pld, u8 index, u8 data);
> > +extern u16 kempld_read16(struct kempld_device_data *pld, u8 index);
> > +extern void kempld_write16(struct kempld_device_data *pld, u8 index, u16 data);
> > +extern u32 kempld_read32(struct kempld_device_data *pld, u8 index);
> > +extern void kempld_write32(struct kempld_device_data *pld, u8 index, u32 data);
> 
> Not really my business, but I think if I was to implement this
> inter-module API I would use regmap for this read/write marshalling
> right here.
I thought about this one and was under the impression that the regmap
API would not let us implement this kind of stuff. I don't see how the
reg_read and reg_write hooks would allow us to implement that, but I may
be missing something here. Maybe Mark can provide some more input.

Cheers,
Samuel.

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