Re: [PATCH v3] serio: PS/2 gpio bit banging driver for the serio bus

[danilokrummrich]

On 2017-08-01 21:07, Dmitry Torokhov wrote:
> On Tue, Aug 01, 2017 at 08:51:40PM +0200, danilokrummrich@xxxxxxxxxxxxx 
> wrote:
> > On 2017-08-01 19:32, Dmitry Torokhov wrote:
> > >On Tue, Aug 01, 2017 at 06:26:14AM +0200, Danilo Krummrich wrote:
> > >>+	irq = gpio_to_irq(drvdata->gpio_clk);
> > >>+	if (!irq) {
> > >>+		dev_err(dev, "cannot get irq from gpio %u\n",
> > >>+			drvdata->gpio_clk);
> > >>+		error = -ENXIO;
> > >>+		goto err_free_serio;
> > >>+	}
> > >
> > >
> > >IRQ line does not have to be the same as GPIO pin. Describe it
> > >separately in device properties and just do:
> > >
> > >	irq = platform_get_irq(pdev, 0);
> > >
> > >and use it in the request below.
> > >
> > In which constellation can they be different?
>
> IIRC there are controllers that may not let you re-configure GPIO that
> is reserved for interrupt, for output. So you could have a bit of
> hardware logic that splits and isolates GPIO and interrupt line.
>
> Also have the trigger come from the interrupt description as well in
> case you happen to have inverter logic there.
Thanks for clarification, didn't knew that. So,I will take this in 
advance.
> > >>+
> > >>+	error = devm_request_irq(dev, irq, ps2_gpio_irq, IRQF_NO_THREAD |
> > >>+			IRQF_TRIGGER_FALLING, DRIVER_NAME, drvdata);
> > >
> > >This will not work if GPIO is behind I2C or other slow bus. Is it
> > >essential that there is no scheduling delay here?
> > >
> > Yes it is. You are right, this wouldn't work. Was this the scenario
> > you had in mind while
> > writing the comment above?
>
> No, that was just a general comment about GPIO on slow busses. You 
> might
> need to check gpiod_can_sleep() and abort driver load if gpio is
> sleeping.
Yes, I will do so.
> Thanks.