October 2017
Intermediate to advanced
586 pages
14h 8m
English
Content preview from Linux Device Drivers Development
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A case study – the GPIO and IRQ chip
Let us consider the following diagram, which ties interrupt controller device to another one which we will use to describe interrupt multiplexing:
mcp23016 IRQ flow
Suppose that you have configured io_1 and io_2 as interrupts. Even if the interrupt happens on io_1 or io_2, the same interrupt line will be triggered to the interrupt controller. Now, the GPIO driver has to read the interrupt status register of the GPIO to find which interrupt (io_1 or io_2) has really fired. Therefore, in this case, a single interrupt line is a multiplex for 16 GPIO interrupts.
Now, let us mangle the original driver of the ...
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