linux-kernel - Re: [PATCH v2] gpiolib: Show correct direction from the beginning

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Message-ID: <CAPybu_33WNiCdkwgNtkiTP2PL+9ai85Z2LiMB6yqNZrV5JdmXw@mail.gmail.com>
Date:   Tue, 2 Oct 2018 09:15:26 +0200
From:   Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Timur Tabi <timur@...nel.org>, Jeffrey Hugo <jhugo@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-gpio <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v2] gpiolib: Show correct direction from the beginning

Hi
On Mon, Oct 1, 2018 at 11:20 PM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Mon, Oct 1, 2018 at 3:36 PM Ricardo Ribalda Delgado
> <ricardo.ribalda@...il.com> wrote:
> > On Mon, Oct 1, 2018 at 1:54 PM Linus Walleij <linus.walleij@...aro.org> wrote:
> > > On Fri, Sep 28, 2018 at 9:30 PM Ricardo Ribalda Delgado
> > > <ricardo.ribalda@...il.com> wrote:
> > >
> > > > How do we proceed from here? Can you fix your driver somehow to
> > > > init the valid mask before enabling the gpio?
> > >
> > > Just include a hunk to the qcom driver reordering this call
> > > at the same time. No need to make it separate patches,
> > > it need to be tested together anyways.
> > >
> > > I guess just switch the order of these two:
> > >
> > >         ret = gpiochip_add_data(&pctrl->chip, pctrl);
> > >         if (ret) {
> > >                 dev_err(pctrl->dev, "Failed register gpiochip\n");
> > >                 return ret;
> > >         }
> > >
> > >         ret = msm_gpio_init_valid_mask(chip, pctrl);
> > >         if (ret) {
> > >                 dev_err(pctrl->dev, "Failed to setup irq valid bits\n");
> > >                 gpiochip_remove(&pctrl->chip);
> > >                 return ret;
> > >         }
> > >
> >
> > the problem is that valid_mask is not a long/integer, is a struct that
> > needs to be malloced, and is malloc at gpiochip_add_data :(
>
> I don't get it, but maybe I'm not smart enough.

Dont take my job, I am the not smart of the conversation :P

>
> gpiochip_add_data() doesn't allocate anything, it
> just adds a already allocated (or static!) gpio_chip
> to the gpiolib subsystem.
>

Take a look to gpiochip_add_data_with_key()
  ->gpiochip_init_valid_mask()
       -> gpiochip->valid_mask = gpiochip_allocate_mask(gpiochip);



> In fact I think it is wrong to set up the mask after
> calling gpiolob_add_data(), because of exactly the
> type of problem you're seeing.

I agree, and I believe that the cleaner way would be to add a function
pointer that replaces:

gpiochip_allocate_mask()
  bitmap_fill(p, chip->ngpio);

with a proper initalization from the driver

But as today the only driver that seems to be using valid_mask is msm,
so perhaps a hack is something better and then when we have a second
driver that requires it we figure out the real requirements. But it is
definately your decision ;)


>
> Don't get confused by the &pctrl->chip
> vs just chip variables, it's just some sloppiness.
>
> Yours,
> Linus Walleij

Thanks!

-- 
Ricardo Ribalda