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

2 files changed, 60 insertions, 1 deletions

diff --git a/include/hw/core/split-irq.h b/include/hw/core/split-irq.h
new file mode 100644
index 0000000000..bb87157c5a
--- /dev/null
+++ b/include/hw/core/split-irq.h
@@ -0,0 +1,57 @@
+/*
+ * IRQ splitter device.
+ *
+ * Copyright (c) 2018 Linaro Limited.
+ * Written by Peter Maydell
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/* This is a simple device which has one GPIO input line and multiple
+ * GPIO output lines. Any change on the input line is forwarded to all
+ * of the outputs.
+ *
+ * QEMU interface:
+ *  + one unnamed GPIO input: the input line
+ *  + N unnamed GPIO outputs: the output lines
+ *  + QOM property "num-lines": sets the number of output lines
+ */
+#ifndef HW_SPLIT_IRQ_H
+#define HW_SPLIT_IRQ_H
+
+#include "hw/irq.h"
+#include "hw/sysbus.h"
+#include "qom/object.h"
+
+#define TYPE_SPLIT_IRQ "split-irq"
+
+#define MAX_SPLIT_LINES 16
+
+typedef struct SplitIRQ SplitIRQ;
+
+#define SPLIT_IRQ(obj) OBJECT_CHECK(SplitIRQ, (obj), TYPE_SPLIT_IRQ)
+
+struct SplitIRQ {
+    DeviceState parent_obj;
+
+    qemu_irq out_irq[MAX_SPLIT_LINES];
+    uint16_t num_lines;
+};
+
+#endif
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