altos/stm: use 0xff for dma mutex value for allocated mutexes

DMA channels which are 'allocated' can't be shared. Instead of using
the value '1' in the related 'mutex', use 0xff which won't match any task.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/src/stm/ao_dma_stm.c b/src/stm/ao_dma_stm.c
index 298a15b5ce58bdd4d67fbe69293c96d22e4dcbc3..93b7fb47e1da815545d843cc2ae4838e65759264 100644 (file)
--- a/src/stm/ao_dma_stm.c
+++ b/src/stm/ao_dma_stm.c
@@ -64,7 +64,7 @@ ao_dma_set_transfer(uint8_t           index,
        if (ao_dma_allocated[index]) {
                if (ao_dma_mutex[index])
                        ao_panic(AO_PANIC_DMA);
-               ao_dma_mutex[index] = 1;
+               ao_dma_mutex[index] = 0xff;
        } else
                ao_mutex_get(&ao_dma_mutex[index]);
        ao_arch_critical(