On Fri, Mar 16, 2012 at 09:17:01AM +0100, David Jander wrote:
> On Fri, 16 Mar 2012 00:20:04 -0700
> Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> wrote:
>
> > Hi David,
> >
> > On Tue, Jun 14, 2011 at 11:08:11AM +0200, David Jander wrote:
> > > Use a threaded interrupt handler in order to permit the handler to use
> > > a GPIO driver that causes things like I2C transactions being done inside
> > > the handler context.
> > > Also, gpio_keys_init needs to be declared as a late_initcall, to make sure
> > > all needed GPIO drivers have been loaded if the drivers are built into the
> > > kernel.
> >
> > Don't want to resurrect the whole initcall discussion, but could you
> > tell me again why the interrup handler needs to be threaded? We do not
> > access hardware from it, hardware is accessed from workqueue context.
> > Here is the ISR in its entirety:
>
> Sorry, the reason described is apparently not very clear. The real reason seems
> to be that I would like this driver to work with I2C GPIO expanders, and its
> the GPIO expanders "interrupt controller" which has itself a threaded handler
> (due to I2C transfers done in it to ack an IRQ). So this is actually a nested
> and threaded interrupt controller (because the IRQ line of the GPIO expander
> is connected to a different GPIO acting itself also as interrupt line).
> In irq/manage.c, function __setup_irq():
>
> ...
> /*
> * Check whether the interrupt nests into another interrupt
> * thread.
> */
> nested = irq_settings_is_nested_thread(desc);
> if (nested) {
> if (!new->thread_fn) {
> ret = -EINVAL;
> goto out_mput;
> }
> ...
>
> This is were requesting a non-threaded IRQ from this GPIO controller will fail.
>
> I know this is not a trivial setup, but IMHO it is very useful (for
> connecting keyboards), and a nice demonstration of the powerful features this
> GPIO driver has :-)
Thanks for the explanation of your setup.
>
> > static irqreturn_t gpio_keys_isr(int irq, void *dev_id)
> > {
> > struct gpio_button_data *bdata = dev_id;
> > const struct gpio_keys_button *button = bdata->button;
> >
> > BUG_ON(irq != gpio_to_irq(button->gpio));
> >
> > if (bdata->timer_debounce)
> > mod_timer(&bdata->timer,
> > jiffies + msecs_to_jiffies(bdata->timer_debounce));
> > else
> > schedule_work(&bdata->work);
> >
> > return IRQ_HANDLED;
> > }
> >
> > It looks to me that non-threaded handler would work as well? Or
> > gpio_to_irq() can sleep with certain chips?
>
> Not in my case. I just checked again. If I change request_threaded_irq() to
> request_irq(), I get this:
>
> ...
> [ 6.409810] gpio-keys gpio_keys.0: Unable to claim irq 0; error -22
> [ 6.416106] gpio-keys: probe of gpio_keys.0 failed with error -22
> ...
>
> This error -22 (-EINVAL) is returned from __setup_irq() (see above).
But the original code used request_any_context_irq() which should have
taken care of your nested IRQ setup:
int request_any_context_irq(unsigned int irq, irq_handler_t handler,
unsigned long flags, const char *name, void *dev_id)
{
struct irq_desc *desc = irq_to_desc(irq);
int ret;
if (!desc)
return -EINVAL;
if (irq_settings_is_nested_thread(desc)) {
ret = request_threaded_irq(irq, NULL, handler,
flags, name, dev_id);
return !ret ? IRQC_IS_NESTED : ret;
}
ret = request_irq(irq, handler, flags, name, dev_id);
return !ret ? IRQC_IS_HARDIRQ : ret;
}
Thanks.
--
Dmitry
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