On Mon, Aug 6, 2012 at 1:56 AM, Daniel Mack <zonque@xxxxxxxxx> wrote: > On 05.08.2012 18:56, Haojian Zhuang wrote: >> On Mon, Aug 6, 2012 at 12:22 AM, Daniel Mack <zonque@xxxxxxxxx> wrote: >>> On 24.07.2012 20:01, Daniel Mack wrote: >>>> On 23.07.2012 18:51, Dmitry Torokhov wrote: >>>>> On Thu, Jul 19, 2012 at 05:36:12PM +0200, Daniel Mack wrote: >>>> >>>>>> Ok, finally I found some time. In general, the patch works fine. The >>>>>> only detail I had to amend was the irqflags, which were changed from >>>>>> IRQF_TRIGGER_RISING/IRQF_TRIGGER_FALLING to >>>>>> IRQF_TRIGGER_HIGH/IRQF_TRIGGER_LOW, which doesn't work as the PXA can't >>>>>> deal with level-based IRQs. Changing this back to RISING/FALLING makes >>>>>> the driver work again. >>>>> >>>>> Hmm, but that would mean we need to restore reading the data in open() >>>>> to make sure we re-arm IRQ in case somebody touched the screen before it >>>>> was opened by userspace... >>>> >>>> I had another look at this and don't really know what to do here. We >>>> definitely need level interrupts for this device as the interrupt line's >>>> level is the only that tells us when we can stop reading from the >>>> device. So it's not just the start condition that bites us here. >>>> >>>> I copied some people that might help find a solution. >>>> >>>> To summarize the problem: The EETI touchscreen is a device that asserts >>>> a GPIO line when it has events to deliver and waits for I2C commands to >>>> empty its buffers. When there are no more buffered events, it will >>>> de-assert the line. >>>> >>>> This device is connected to a PXA GPIO that is only able to deliver edge >>>> IRQs, and the old implemenation was to wait for an interrupt and then >>>> read data as long as the IRQ's corresponding GPIO was asserted. However, >>>> expecting that an IRQ is mappable to a GPIO is not something we should >>>> do, so the only clean solution is to teach the PXA GPIO controller level >>>> IRQs. >>>> >>>> So it boils down to the question: Is there any easy and generic way to >>>> emulate level irq on chips that don't support that natively? >>> >>> Otherwise, we would need some sort of generic irq_to_gpio() again, and >>> the interrupt line the driver listens to must have support for that sort >>> of mapping. >>> >>> Any opinion on this, anyone? >>> >> Since you're using gpio as input, you need to call gpio_request() and set it >> as input direction. And you could also transfer the gpio number into touch >> driver via platform data. Is it OK for you? > > No, that's not the point. What we get via the i2c runtime data is an > interrupt number. The driver is driven by that interrupt and doesn't > poll on a GPIO line, which is how it should be. > > However, in order to know when to stop reading from the device, we need > to monitor the GPIO line after the interrupt has arrived, and read as > long as the line is asserted. Then we stop reading and wait for the next > interrupt to arrive. > > Hence, what we need here is either a GPIO/IRQ controller that is able to > handle level-IRQs (which the PXA can't do), or we need to have a generic > way to map IRQ lines back to GPIOs. > > Of course, I could pass the GPIO in the platform data and the IRQ in the > I2C data and leave it to the user of the driver to keep both values in > sync, but I wanted to avoid that. I see no better way except to encode the GPIO line into the platform data. In order to solve the sync issue, I personally think mapping the GPIO to IRQ would be better here, and ignore the irq value from the I2C data. A forward mapping of gpio_to_irq() will be less problematic here, and for those platforms where gpio_to_irq() returns invalid, those platforms are probably not desirable for this chip. So my understanding, if it's correct, that we can treat the EETI chip as having two separate inputs: one IRQ line (for the event notification) and one GPIO line (for a condition where data are emptied), we could naturally have two numbers in the driver, but unfortunately they end up being in sync as they are physically one pin. And Daniel, I haven't looked into the driver myself, I guess you might need to change the pin role to GPIO with GPIO API explicitly at run-time, e.g. gpio_direction_input() followed by gpio_get_value(), but I believe you should have already done that good enough as always :-) -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
