Re: [PATCH 5/6] mtd: rawnand: ams-delta: use GPIO lookup table

Janusz Krzysztofik
2018-05-18T23:15:29Z

On Friday, May 18, 2018 11:21:14 PM CEST Andy Shevchenko wrote:
> On Sat, May 19, 2018 at 12:09 AM, Janusz Krzysztofik
>
> <jmkrzyszt@gmail.com> wrote:
> > + gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy", GPIOD_IN);
> > + if (!IS_ERR_OR_NULL(gpiod_rdy)) {
>
> So, is it optional or not at the end?
> If it is, why do we check for NULL?

As far as I can understand, nand_chip->dev_ready() callback is optional.
That's why I decided to use the _optional variant of devm_gpiod_get(). In case
of ams-delta, the dev_ready() callback depends on availability of the 'rdy'
GPIO pin. As a consequence, I'm checking for both NULL and ERR in order to
decide if dev_ready() will be supported.

I can pretty well replace it with the standard form and check for ERR only if
the purpose of the _optional form is different.

> > this->dev_ready = ams_delta_nand_ready;
> >
> > } else {
> >
> > this->dev_ready = NULL;
> > pr_notice("Couldn't request gpio for Delta NAND
> > ready.\n");
>
> dev_notice() ?

Sure, but maybe in a separate patch? That's not a new code just being added
but an existing one, not the merit of the change.

> > }
> >
> > +err_gpiod:
> > + if (err == -ENODEV || err == -ENOENT)
> > + err = -EPROBE_DEFER;
>
> Hmm...

Amstrad Delta uses gpio-mmio driver. Unfortunatelty that driver is not
availble before device init phase, unlike other crucial GPIO drivers which are
initialized earlier, e.g. during the postcore or at latetst the subsys phase.
Hence, devices which depend on GPIO pins provided by gpio-mmio must either be
declared late or fail softly so they get another chance of being probed
succesfully.

I thought of replacing the gpio-mmio platform driver with bgpio functions it
exports but for now I haven't implemented it, not even shared the idea.

Does it really hurt to return -EPROBE_DEFER if a GPIO pin can't be obtained?

Thanks,
Janusz