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One of the largest OS data structures is the vector table, {{g_irqvector\[]}}. This is the table that holds the vector information when {{irq_attach()}} is called and used to dispatch interrupts by {{irq_dispatch()}}. Recent changes have made that table even larger, for 32-bit arm the size of that table is given by: |
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nbytes = number_of_interrupts * (2 * sizeof(void *))
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We will focus on the STM32 for this discussion to keep things simple. However, this discussion applies to all architectures.
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{{irq_attach()}} would this use this index to set the g_irqvector\[]. |
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g_irqvector[ndx].handler = isr;
g_irqvector[ndx].arg = arg;
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irq_dispatch()
irq_dispatch() is called by MCU logic when an interrupt is received:
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{{irq_initialize()}}: simply set the {{g_irqvector\[]}} table a known state on power-up. It would only have to distinquish the difference in sizes. |
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#ifdef CONFIG_ARCH_MINIMAL_VECTORTABLE
# define TAB_SIZE CONFIG_ARCH_NUSER_INTERRUPTS
#else
# define TAB_SIZE NR_IRQS
#endif
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for (i = 0; i < TAB_SIZE; i++)
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An implementation of up_mapirq() might be something like:
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{{g_irqmap\[]}} is a array of mapped irq table indices. It contains the mapped index value and is itself indexed by the physical interrupt vector number. It provides an {{irq_mapped_t}} value in the range of 0 to {{CONFIG_ARCH_NUSER_INTERRUPTS}} that is the new, mapped index into the vector table. Unsupported IRQs would simply map to an out of range value like {{IRQMAPPED_MAX}}. So, for example, if {{g_irqmap\[37] |
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24}}, then the hardware interrupt vector 37 will be mapped to the interrupt vector table at index 24. if {{g_irqmap\[42] IRQMAPPED_MAX}}, then hardware interrupt vector 42 is not used and if it occurs will result in an unexpected interrupt crash. |
Hardware Vector Remapping
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