Re: [PATCH 1/2] iio: imu: st_lsm6dsx: support open drain mode

On Sun, Jun 25, 2017 at 11:34 AM, Lorenzo Bianconi
[off-list ref] wrote:

quoted

In common with the mpu3050 which was the first driver in IIO to do open drain,

I think I implemented it on the ST sensors first actually.

quoted

I think you need to think about precedence as we allow for IRQF_RISING
and IRQF_FALLING already.  Open drain only allows for shared interrupts
if IRQF_FALLING (I think)

quoted

      err = devm_request_threaded_irq(hw->dev, hw->irq,
                                      st_lsm6dsx_handler_irq,
                                      st_lsm6dsx_handler_thread,

I have not got the difference between IRQF_RISING and IRQF_FALLING
when the irq line
is marked as shared (when open drain is enabled).
Looking at the code, mpu3050 gyro sensor does not support shared interrupts
with IRQF_RISING and IRQF_TRIGGER_HIGH. Is it a hw limitation?

It seems like I have inverted the logic in the MPU3050 driver.
I'll send a patch.

Speaking with digital designer, lsm6dsx series allows open drain mode
even if the requested irq line
is IRQF_TRIGGER_HIGH or IRQF_RISING, we need to add a pull-down resistor.
Moreover ST framework already supports open drain if the requested
interrupt is IRQF_RISING.

This seems correct.

Yours,
Linus Walleij