hw/core/split-irq: Device that splits IRQ lines

In some board or SoC models it is necessary to split a qemu_irq line
so that one input can feed multiple outputs.  We currently have
qemu_irq_split() for this, but that has several deficiencies:
 * it can only handle splitting a line into two
 * it unavoidably leaks memory, so it can't be used
   in a device that can be deleted

Implement a qdev device that encapsulates splitting of IRQs, with a
configurable number of outputs.  (This is in some ways the inverse of
the TYPE_OR_IRQ device.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180220180325.29818-13-peter.maydell@linaro.org

1 files changed, 3 insertions, 1 deletions

diff --git a/include/hw/irq.h b/include/hw/irq.h
index 4c4c2eaf9a..7a40e3ed26 100644
--- a/include/hw/irq.h
+++ b/include/hw/irq.h
@@ -50,7 +50,9 @@ void qemu_free_irq(qemu_irq irq);
 /* Returns a new IRQ with opposite polarity.  */
 qemu_irq qemu_irq_invert(qemu_irq irq);
 
-/* Returns a new IRQ which feeds into both the passed IRQs */
+/* Returns a new IRQ which feeds into both the passed IRQs.
+ * It's probably better to use the TYPE_SPLIT_IRQ device instead.
+ */
 qemu_irq qemu_irq_split(qemu_irq irq1, qemu_irq irq2);
 
 /* Returns a new IRQ set which connects 1:1 to another IRQ set, which