[ECOS] at91 SPI driver, use of cyg_drv_dsr_lock()

[Peter Kooiman]

Hello all,

I cannot for the life of me get my head around this code in spi_at91.c (in 
packages\devs\spi\arm\at91\current\src), function spi_at91_transfer:


            // Unmask the SPI int
            cyg_drv_interrupt_unmask(CYGNUM_HAL_INTERRUPT_SPI);

            // Wait for its completition
            cyg_drv_dsr_lock();
            {
                while (!spi_bus->transfer_end)
                    cyg_drv_cond_wait(&spi_bus->transfer_cond);
            }
            cyg_drv_dsr_unlock();

Now, the condition variable spi_bus->transfer_cond is signalled from the 
DSR:
        // Transfer ended
        spi_bus->transfer_end = true;
        cyg_drv_cond_signal(&spi_bus->transfer_cond);

However, if I understand correctly, cyg_drv_dsr_lock() will prevent the 
(any) DSR from being run, so...while holding the DSR lock the code waits for 
a condition variable that must be signalled from the DSR that we have just 
prevented from running in the first place??

Either I completely misunderstand the way cyg_drv_dsr_lock() works (very 
possible), or this code is broken...anyone care to comment?

Regards
Peter




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