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

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Date:   Sun, 20 May 2018 17:37:44 +0200
From:   Janusz Krzysztofik <jmkrzyszt@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Tony Lindgren <tony@...mide.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Mark Brown <broonie@...nel.org>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Richard Weinberger <richard@....at>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Jarkko Nikula <jarkko.nikula@...mer.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-input <linux-input@...r.kernel.org>,
        "open list:MEMORY TECHNOLOGY..." <linux-mtd@...ts.infradead.org>,
        linux-fbdev@...r.kernel.org,
        ALSA Development Mailing List <alsa-devel@...a-project.org>
Subject: Re: [PATCH 5/6] mtd: rawnand: ams-delta: use GPIO lookup table

On Sunday, May 20, 2018 4:44:31 PM CEST Andy Shevchenko wrote:
> On Sun, May 20, 2018 at 12:55 AM, Janusz Krzysztofik
> 
> <jmkrzyszt@...il.com> wrote:
> > On Saturday, May 19, 2018 8:00:38 PM CEST Andy Shevchenko wrote:
> >> On Sat, May 19, 2018 at 2:15 AM, Janusz Krzysztofik <jmkrzyszt@...il.com>
> > 
> > wrote:
> >> NULL check in practice discards the _optional part of gpiod_get(). So,
> >> either you use non-optional variant and decide how to handle an
> >> errors, or user _optional w/o NULL check.
> > 
> > OK, I'm going to use something like the below while submitting v2:
> > 
> > -       gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy", GPIOD_IN);
> > -       if (!IS_ERR_OR_NULL(gpiod_rdy)) {
> > -               this->dev_ready = ams_delta_nand_ready;
> > -       } else {
> > -               this->dev_ready = NULL;
> > -               pr_notice("Couldn't request gpio for Delta NAND
> > ready.\n");
> > +       priv->gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy",
> > +                                                 GPIOD_IN);
> > +       if (IS_ERR(priv->gpiod_rdy)) {
> > +               err = PTR_ERR(priv->gpiod_nwp);
> > +               dev_warn(&pdev->dev, "RDY GPIO request failed (%d)\n",
> > err); +               goto err_gpiod;
> > 
> >         }
> > 
> > +       if (priv->gpiod_rdy)
> > +               this->dev_ready = ams_delta_nand_ready;
> 
> This makes sense.
> 
> Though, I completely dislike "rdy" name of GPIO. Where is it documented?

No documentation files for Amstrad Delta nor for its NAND driver specifically 
exist under Documentation/. However, there exist some for generic GPIO NAND 
driver where the pin name "rdy" is used explicitly:
Documentation/driver-api/gpio/drivers-on-gpio.rst
Documentation/devicetree/bindings/mtd/gpio-control-nand.txt
You can find that mnemonic used across drivers/mtd/nand/, standalone or as a 
suffix, including the Amstrad Delta NAND driver before the change discussed.

To be honest, I don't like it much either, but I'm just using it instead of 
inventing something new.

Thanks,
Janusz