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[Bug 1001456] HAL misses Interrupt Clear-Pending Registers handling:wasted processing power

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--- Comment #14 from Bernard Fouchà <> 2012-02-15 11:28:54 GMT ---
(In reply to comment #13)
> Changes to the Kernel should be done with caution. I think that this addition
> is not necessary. The desired functionality, for a given platform, can be
> introduced by #defining HAL_VAR_INTERRUPT_ACKNOWLEDGE (and/or its cousins).

There are two problems:

- clearing the pending interrupt bit is completely different from acknowledging
an interrupt. Acknowledgment is usually done at the end of DSR/ISR while
clearing the pending interrupt bit must be done *before* reading the peripheral
registers describing interrupt source(s): HAL_VAR_INTERRUPT_ACKNOWLEDGE is not
a solution.

- if HAL_VAR_INTERRUPT_CLEAR_PENDING is added only to Cortex-M targets, then
how can one share a driver between an arch not requiring clearing pending
interrupt and Cortex-M cores? For instance the generic serial 16x5x driver?
Today cyg_drv_interrupt_acknowledge() resolves to CYG_EMPTY_STATEMENT for
Cortex-M, IMHO we need cyg_drv_interrupt_clear_pending() to resolve to
CYG_EMPTY_STATEMENT for non-Cortex-M, hence one can write a driver using both
cyg_drv_interrupt_acknowledge() and cyg_drv_interrupt_clear_pending() at the
correct place so the driver can work in different arch.

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