On Mon, Jun 17, 2024 at 11:07 AM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> On Mon, Jun 17, 2024 at 10:56 AM Marek Behún <kabel@xxxxxxxxxx> wrote:
> > On Mon, 17 Jun 2024 10:38:31 +0200
> > Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> > > On Wed, Jun 5, 2024 at 9:00 PM Andy Shevchenko
> > > <andy.shevchenko@xxxxxxxxx> wrote:
> > > > On Wed, Jun 5, 2024 at 7:19 PM Marek Behún <kabel@xxxxxxxxxx> wrote:
> > > > >
> > > > > Add support for true random number generator provided by the MCU.
> > > > > New Omnia boards come without the Atmel SHA204-A chip. Instead the
> > > > > crypto functionality is provided by new microcontroller, which has
> > > > > a TRNG peripheral.
> > > >
> > > > +Cc: Bart for gpiochip_get_desc() usage.
...
> > > > > + irq_idx = omnia_int_to_gpio_idx[__bf_shf(OMNIA_INT_TRNG)];
> > > > > + irq = gpiod_to_irq(gpiochip_get_desc(&mcu->gc, irq_idx));
> > > > > + if (irq < 0)
> > > > > + return dev_err_probe(dev, irq, "Cannot get TRNG IRQ\n");
> > > >
> > > > Okay, it's a bit more complicated than that. The gpiochip_get_desc()
> > > > shouldn't be used. Bart, what can you suggest to do here? Opencoding
> > > > it doesn't sound to me a (fully) correct approach in a long term.
> > >
> > > Andy's worried about reference counting of the GPIO device. Maybe you
> > > should just ref the GPIO device in irq_request_resources() and unref
> > > it in irq_release_resources()? Then you could use gpiochip_get_desc()
> > > just fine.
> >
> > But this is already being done.
> >
> > The irqchip uses GPIOCHIP_IRQ_RESOURCE_HELPERS macro in its definition:
> >
> > static const struct irq_chip omnia_mcu_irq_chip = {
> > ...
> > GPIOCHIP_IRQ_RESOURCE_HELPERS,
> > };
> >
> > This means that gpiochip_irq_reqres() and gpiochip_irq_relres() are
> > used as irq_request_resources() and irq_release_resources().
> >
> > The gpiochip_reqres_irq() code increases the module refcount and even
> > locks the line as IRQ:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpio/gpiolib.c?h=v6.10-rc4#n3732
>
> Andy: what is the issue here then exactly?
The function in use is marked as DEPRECATED. If you are fine with its
usage in this case, I have no issues with it.
If you want it to be replaced with the respective
gpio_device_get_desc(), it's fine, but then the question is how
properly get a pointer to GPIO device object.
--
With Best Regards,
Andy Shevchenko
