Re: [PATCH v6 07/11] platform: cznic: turris-omnia-mcu: Add support for MCU provided TRNG

["Marek Behún" <kabel@kernel.org>]

On Tue, 23 Apr 2024 19:43:41 +0300
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Tue, Apr 23, 2024 at 7:32 PM Marek Behún <kabel@kernel.org> wrote:
> > On Tue, 23 Apr 2024 18:58:19 +0300
> > Andy Shevchenko <andy@kernel.org> wrote:  
> > > On Thu, Apr 18, 2024 at 02:11:12PM +0200, Marek Behún wrote:  
> 
> ...
> 
> > > > +   irq_idx = omnia_int_to_gpio_idx[__bf_shf(INT_TRNG)];
> > > > +   irq = devm_irq_create_mapping(dev, mcu->gc.irq.domain, irq_idx);
> > > > +   if (irq < 0)
> > > > +           return dev_err_probe(dev, irq, "Cannot map TRNG IRQ\n");  
> > >
> > > This looks like some workaround against existing gpiod_to_irq(). Why do you
> > > need this?  
> >
> > Hmmm, I thought that would not work because that line is only valid
> > as an IRQ, not as a GPIO (this is enforced via the valid_mask member of
> > gpio_chip and gpio_irq_chip).
> >
> > But looking at the code of gpiolib, if I do
> >   irq = gpiod_to_irq(gpiochip_get_desc(gc, irq_idx));
> > the valid_mask is not enforced anywhere.  
> 
> Which one? GPIO has two: one per GPIO realm and one for IRQ domain.

The GPIO line validity is not enforced. The IRQ line validity is
enforced in the gpiochip_to_irq() method.

> > Is this semantically right to do even in spite of the fact that the
> > line is not a valid GPIO line?  
> 
> Yes. It's orthogonal to that.
>