[Qemu-devel] [PATCH RFC 2/3] sysbus: Allow sysbus MMIO passthrough

[Peter Maydell <peter.maydell@linaro.org>]

Add new function sysbus_pass_mmio() to allow a sysbus device to
delegate MMIO to another sysbus device. This allows a limited
form of composition for sysbus devices.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/sysbus.c |   26 ++++++++++++++++++++++++++
 hw/sysbus.h |    3 +++
 2 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/hw/sysbus.c b/hw/sysbus.c
index 01ebe47..793b0c1 100644
--- a/hw/sysbus.c
+++ b/hw/sysbus.c
@@ -43,6 +43,10 @@ void sysbus_mmio_unmap(SysBusDevice *dev, int n)
 {
     assert(n >= 0 && n < dev->num_mmio);
 
+    if (dev->mmio[n].delegate) {
+        sysbus_mmio_unmap(dev->mmio[n].delegate, dev->mmio[n].delegate_mmio);
+        return;
+    }
     if (dev->mmio[n].addr == (target_phys_addr_t)-1) {
         /* region already unmapped */
         return;
@@ -60,6 +64,11 @@ void sysbus_mmio_map(SysBusDevice *dev, int n, target_phys_addr_t addr)
 {
     assert(n >= 0 && n < dev->num_mmio);
 
+    if (dev->mmio[n].delegate) {
+        sysbus_mmio_map(dev->mmio[n].delegate, dev->mmio[n].delegate_mmio,
+                        addr);
+        return;
+    }
     if (dev->mmio[n].addr == addr) {
         /* ??? region already mapped here.  */
         return;
@@ -83,6 +92,11 @@ void sysbus_mmio_resize(SysBusDevice *dev, int n, target_phys_addr_t newsize)
     target_phys_addr_t addr;
     assert(n >= 0 && n < dev->num_mmio);
 
+    if (dev->mmio[n].delegate) {
+        sysbus_mmio_resize(dev->mmio[n].delegate, dev->mmio[n].delegate_mmio,
+                           newsize);
+        return;
+    }
     if (newsize != dev->mmio[n].size) {
         addr = dev->mmio[n].addr;
         if (addr != (target_phys_addr_t)-1) {
@@ -127,6 +141,7 @@ void sysbus_init_mmio(SysBusDevice *dev, target_phys_addr_t size,
 
     assert(dev->num_mmio < QDEV_MAX_MMIO);
     n = dev->num_mmio++;
+    dev->mmio[n].delegate = 0;
     dev->mmio[n].addr = -1;
     dev->mmio[n].size = size;
     dev->mmio[n].iofunc = iofunc;
@@ -139,11 +154,22 @@ void sysbus_init_mmio_cb(SysBusDevice *dev, target_phys_addr_t size,
 
     assert(dev->num_mmio < QDEV_MAX_MMIO);
     n = dev->num_mmio++;
+    dev->mmio[n].delegate = 0;
     dev->mmio[n].addr = -1;
     dev->mmio[n].size = size;
     dev->mmio[n].cb = cb;
 }
 
+void sysbus_pass_mmio(SysBusDevice *dev, SysBusDevice *target, int target_mmio)
+{
+    int n;
+
+    assert(dev->num_mmio < QDEV_MAX_MMIO);
+    n = dev->num_mmio++;
+    dev->mmio[n].delegate = target;
+    dev->mmio[n].delegate_mmio = target_mmio;
+}
+
 void sysbus_init_ioports(SysBusDevice *dev, pio_addr_t ioport, pio_addr_t size)
 {
     pio_addr_t i;
diff --git a/hw/sysbus.h b/hw/sysbus.h
index 70e2488..789e4c5 100644
--- a/hw/sysbus.h
+++ b/hw/sysbus.h
@@ -19,6 +19,8 @@ struct SysBusDevice {
     qemu_irq *irqp[QDEV_MAX_IRQ];
     int num_mmio;
     struct {
+        SysBusDevice *delegate;
+        int delegate_mmio;
         target_phys_addr_t addr;
         target_phys_addr_t size;
         mmio_mapfunc cb;
@@ -46,6 +48,7 @@ void sysbus_init_mmio(SysBusDevice *dev, target_phys_addr_t size,
                       ram_addr_t iofunc);
 void sysbus_init_mmio_cb(SysBusDevice *dev, target_phys_addr_t size,
                             mmio_mapfunc cb);
+void sysbus_pass_mmio(SysBusDevice *dev, SysBusDevice *target, int target_mmio);
 void sysbus_init_irq(SysBusDevice *dev, qemu_irq *p);
 void sysbus_pass_irq(SysBusDevice *dev, SysBusDevice *target);
 void sysbus_init_ioports(SysBusDevice *dev, pio_addr_t ioport, pio_addr_t size);
-- 
1.7.1