linux-kernel - Re: [PATCH] [v2] at86rf230: convert to gpio descriptors

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Date:   Wed, 1 Feb 2023 08:20:57 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        linux-wpan@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] [v2] at86rf230: convert to gpio descriptors

Hi Miquel,

On Wed, Feb 01, 2023 at 09:33:32AM +0100, Miquel Raynal wrote:
> Hi Dmitry,
> 
> dmitry.torokhov@...il.com wrote on Tue, 31 Jan 2023 16:50:07 -0800:
> 
> > On Tue, Jan 31, 2023 at 3:52 PM Dmitry Torokhov
> > <dmitry.torokhov@...il.com> wrote:
> > >
> > > Hi Arnd,
> > >
> > > On Thu, Jan 26, 2023 at 8:32 AM Arnd Bergmann <arnd@...nel.org> wrote:  
> > > >
> > > >         /* Reset */
> > > > -       if (gpio_is_valid(rstn)) {
> > > > +       if (rstn) {
> > > >                 udelay(1);
> > > > -               gpio_set_value_cansleep(rstn, 0);
> > > > +               gpiod_set_value_cansleep(rstn, 0);
> > > >                 udelay(1);
> > > > -               gpio_set_value_cansleep(rstn, 1);
> > > > +               gpiod_set_value_cansleep(rstn, 1);  
> > >
> > > For gpiod conversions, if we are not willing to chase whether existing
> > > DTSes specify polarities
> > > properly and create workarounds in case they are wrong, we should use
> > > gpiod_set_raw_value*()
> > > (my preference would be to do the work and not use "raw" variants).
> > >
> > > In this particular case, arch/arm/boot/dts/vf610-zii-dev-rev-c.dts
> > > defines reset line as active low,
> > > so you are leaving the device in reset state.
> 
> You mean the semantics of gpio_set_value() gpiod_set_value() are
> different? Looking at your patch it looks like gpio_set_value() asserts
> a physical line state (high or low) while gpiod_set_value() would
> actually try to assert a logical state (enabled or disabled) with the
> meaning of those being possibly inverted thanks to the DT polarities.
> Am I getting this right?

Right. If one wants to do physical levels, they need to use gpiod "raw"
APIs.

Thanks.

-- 
Dmitry