linux-kernel - Re: [PATCH v3 1/3] gpiolib: convert 'devprop_gpiochip_set_names' to support multiple gpiochip banks per device

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Date:   Wed, 28 Jul 2021 06:05:03 +0200
From:   Sergio Paracuellos <sergio.paracuellos@...il.com>
To:     Gregory Fong <gregory.0xf0@...il.com>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        René van Dorst <opensource@...rst.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        John Thomson <git@...nthomson.fastmail.com.au>,
        NeilBrown <neil@...wn.name>,
        Nicholas Mc Guire <hofrat@...dl.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] gpiolib: convert 'devprop_gpiochip_set_names' to
 support multiple gpiochip banks per device

On Wed, Jul 28, 2021 at 1:15 AM Gregory Fong <gregory.0xf0@...il.com> wrote:
>
> On Tue, Jul 27, 2021 at 8:20 AM Sergio Paracuellos
> <sergio.paracuellos@...il.com> wrote:
> >
> > The default gpiolib-of implementation does not work with the multiple
> > gpiochip banks per device structure used for example by the gpio-mt7621
> > and gpio-brcmstb drivers. To fix these kind of situations driver code
> > is forced to fill the names to avoid the gpiolib code to set names
> > repeated along the banks. Instead of continue with that antipattern
> > fix the gpiolib core function to get expected behaviour for every
> > single situation adding a field 'offset' in the gpiochip structure.
> > Doing in this way, we can assume this offset will be zero for normal
> > driver code where only one gpiochip bank per device is used but
> > can be set explicitly in those drivers that really need more than
> > one gpiochip.
> >
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
>
> One minor comment below, then this looks great:
> Reviewed-by: Gregory Fong <gregory.0xf0@...il.com>
>
> > Signed-off-by: Sergio Paracuellos <sergio.paracuellos@...il.com>
> > ---
> >  drivers/gpio/gpiolib.c      | 32 +++++++++++++++++++++++++++-----
> >  include/linux/gpio/driver.h |  4 ++++
> >  2 files changed, 31 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index 27c07108496d..84ed4b73fa3e 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -382,10 +382,18 @@ static int devprop_gpiochip_set_names(struct gpio_chip *chip)
> >         if (count < 0)
> >                 return 0;
> >
> > -       if (count > gdev->ngpio) {
> > -               dev_warn(&gdev->dev, "gpio-line-names is length %d but should be at most length %d",
> > -                        count, gdev->ngpio);
> > -               count = gdev->ngpio;
> > +       /*
> > +        * When offset is set in the driver side we assume the driver internally
> > +        * is using more than one gpiochip per the same device. We have to stop
> > +        * setting friendly names if the specified ones with 'gpio-line-names'
> > +        * are less than the offset in the device itself. This means all the
> > +        * lines are not present for every single pin within all the internal
> > +        * gpiochips.
> > +        */
> > +       if (count <= chip->offset) {
> > +               dev_warn(&gdev->dev, "gpio-line-names too short (length %d) cannot map names for the gpiochip at offset %u\n",
>
> nit: there should be some punctuation after "(length %d)", otherwise
> with parentheticals removed it reads as
>
> "gpio-line-names too short cannot map names ..."
>
> but we need to provide a space between these thoughts for clarity.  A
> comma should be ok:
>
> "gpio-line-names too short (length %d), cannot map names ..."

Will add it, thanks.

Best regards,
     Sergio Paracuellos
>
> Best regards,
> Gregory