gpio generic driver

gpio generic driver

[Barbier, Renaud]

Question regarding the function below:

static int bgpio_get(struct gpio_chip *gc, unsigned int gpio)
  {
          struct bgpio_chip *bgc = to_bgpio_chip(gc);

~         return bgc->read_reg(bgc->reg_dat) & bgc->pin2mask(bgc, gpio);
  }

This returns the value from the register i.e the value as in 0x01000000 for bit 3BE or 28LE. This is what I see using the drivers/gpio/gpio-mpc8xxx.c driver.

Is it not supposed to return just 0 or 1?

Linux has

return !!(gc->read_reg(gc->reg_dat) & bgpio_line2mask(gc, gpio));

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Re: gpio generic driver

[Lucas Stach]

Am Donnerstag, den 23.07.2020, 19:51 +0000 schrieb Barbier, Renaud:
> Question regarding the function below:
> 
> static int bgpio_get(struct gpio_chip *gc, unsigned int gpio)
>   {
>           struct bgpio_chip *bgc = to_bgpio_chip(gc);
> 
> ~         return bgc->read_reg(bgc->reg_dat) & bgc->pin2mask(bgc, gpio);
>   }
> 
> This returns the value from the register i.e the value as in 0x01000000 for bit 3BE or 28LE. This is what I see using the drivers/gpio/gpio-mpc8xxx.c driver.
> 
> Is it not supposed to return just 0 or 1?
> 
> Linux has
> 
> return !!(gc->read_reg(gc->reg_dat) & bgpio_line2mask(gc, gpio));

This shouldn't make a difference when the return value is just used in
a condition, but it may confuse other uses which expect the normalized
1/0 form.

Care to send a patch to change this to the more correct Linux version?

Regards,
Lucas


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RE: gpio generic driver

[Barbier, Renaud]

Of course. Preparing a patch

> -----Original Message-----
> From: Lucas Stach [mailto:l.stach@pengutronix.de]
> Sent: 24 July 2020 09:20
> To: Barbier, Renaud <renaud.barbier@abaco.com>;
> barebox@lists.infradead.org
> Subject: Re: gpio generic driver
> 
> 
> 
> [**EXTERNAL SOURCE**]:Please verify the source before clicking link or
> opening attachment.
> 
> Am Donnerstag, den 23.07.2020, 19:51 +0000 schrieb Barbier, Renaud:
> > Question regarding the function below:
> >
> > static int bgpio_get(struct gpio_chip *gc, unsigned int gpio)
> >   {
> >           struct bgpio_chip *bgc = to_bgpio_chip(gc);
> >
> > ~         return bgc->read_reg(bgc->reg_dat) & bgc->pin2mask(bgc, gpio);
> >   }
> >
> > This returns the value from the register i.e the value as in 0x01000000 for
> bit 3BE or 28LE. This is what I see using the drivers/gpio/gpio-mpc8xxx.c
> driver.
> >
> > Is it not supposed to return just 0 or 1?
> >
> > Linux has
> >
> > return !!(gc->read_reg(gc->reg_dat) & bgpio_line2mask(gc, gpio));
> 
> This shouldn't make a difference when the return value is just used in
> a condition, but it may confuse other uses which expect the normalized
> 1/0 form.
> 
> Care to send a patch to change this to the more correct Linux version?
> 
> Regards,
> Lucas

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