On Wed, Apr 4, 2018 at 10:00 PM, H. Nikolaus Schaller hns@goldelico.com wrote:
in driver code. Therefore, the pca953x driver rejects the setup of the irq because it can only handle EDGE interrupts so far.
This hack translates level interrupts to edge interrupts for the pca953x chips. This is enough for initial testing, but not a good solution since interrupts may be lost.
If for example the connected chip requests a IRQ_TYPE_LEVEL_LOW this may have the reason that there may be multiple different interrupt sources in the chip - wired-or together to the input of the pca953x. Now if we do edge detecion only, the first interrupt will generate an EDGE_FALLING, but a second one won't ever if the first interrupt wasn't already processed.
IMHO a better solution would be to make the pca953x interrupt handler check if the irq input is still in the active level and run the device specific handler again.
What I thought about is to enable such exclusively for "L" variants of the chips and check latched values.