Re: [PATCH v4 2/2] i2c: mux: ltc4306: LTC4306 and LTC4305 I2C multiplexer/switch

[Michael Hennerich]

On 06.04.2017 22:03, Peter Rosin wrote:
> On 2017-04-06 13:31, Michael Hennerich wrote:
> > On 06.04.2017 10:39, Peter Rosin wrote:

Hi Peter,

again - thanks for your review.
Comments below.

> > > > +static const struct regmap_config ltc4306_regmap_config = {
> > > > +	.reg_bits = 8,
> > > > +	.val_bits = 8,
> > > > +	.max_register = LTC_REG_SWITCH,
> > > > +	.volatile_reg = ltc4306_is_volatile_reg,
> > > > +	.cache_type = REGCACHE_RBTREE,
> > >
> > > Did you consider REGCACHE_FLAT? There are very few registers and no hole
> > > in the map, and maintaining a tree seems like total overkill.
> >
> > There is no reason to use REGCACHE_FLAT, in our case it will be a single
> > node.
>
> Ok, so that makes me wonder what need REGCACHE_FLAT satisfies? To me,
> a flat regmap seems like a perfect fit here. Oh well...

https://lkml.org/lkml/2012/12/19/172

It's not worth arguing - if you prefer FLAT - then it's FLAT
While it's still round :-)


> > > > +static int ltc4306_gpio_init(struct ltc4306 *data)
> > > > +{
> > > > +	struct device *dev = regmap_get_device(data->regmap);
> > > > +
> > > > +	if (!data->chip->num_gpios)
> > > > +		return 0;
> > > > +
> > > > +	data->gpiochip.label = dev_name(dev);
> > > > +	data->gpiochip.base = -1;
> > > > +	data->gpiochip.ngpio = data->chip->num_gpios;
> > > > +	data->gpiochip.parent = dev;
> > > > +	data->gpiochip.can_sleep = true;
> > > > +	data->gpiochip.direction_input = ltc4306_gpio_direction_input;
> > > > +	data->gpiochip.direction_output = ltc4306_gpio_direction_output;
> > >
> > > I'm missing a get_direction op?
> >
> > No - its purely optional - the vast majority of gpiochips don't
> > implement it.
> >
> > linux/drivers/gpio$ grep -lr --include \*.c get_direction | wc
> >       36      36     523
> > linux/drivers/gpio$ grep -Lr --include \*.c get_direction | wc
> >      101     101    1461
>
> Ok, but while optional, why not provide it? The implementation would
> be about as simple as ltc4306_gpio_get, no?

ok - convinced me.


I'll send version 5 shortly.


--
Greetings,
Michael

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