[PATCH v4 3/7] iommu/arm: Add iommu_dt_xlate()

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

Move code for processing DT IOMMU specifier to a separate helper.
This helper will be re-used for adding PCI devices by the subsequent
patches as we will need exact the same actions for processing
DT PCI-IOMMU specifier.

While at it introduce NO_IOMMU to avoid magic "1".

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
v3->v4:
* make dt_phandle_args *iommu_spec const
* move !ops->add_device check to helper

v2->v3:
* no change

v1->v2:
* no change

downstream->v1:
* trivial rebase
* s/dt_iommu_xlate/iommu_dt_xlate/

(cherry picked from commit c26bab0415ca303df86aba1d06ef8edc713734d3 from
 the downstream branch poc/pci-passthrough from
 https://gitlab.com/xen-project/people/bmarquis/xen-arm-poc.git)
---
 xen/drivers/passthrough/device_tree.c | 47 ++++++++++++++++++---------
 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git a/xen/drivers/passthrough/device_tree.c 
b/xen/drivers/passthrough/device_tree.c
index c60e78eaf556..ff9e66ebf92a 100644
--- a/xen/drivers/passthrough/device_tree.c
+++ b/xen/drivers/passthrough/device_tree.c
@@ -127,15 +127,42 @@ int iommu_release_dt_devices(struct domain *d)
     return 0;
 }
 
+/* This correlation must not be altered */
+#define NO_IOMMU    1
+
+static int iommu_dt_xlate(struct device *dev,
+                          const struct dt_phandle_args *iommu_spec)
+{
+    const struct iommu_ops *ops = iommu_get_ops();
+    int rc;
+
+    if ( !ops->dt_xlate )
+        return -EINVAL;
+
+    if ( !dt_device_is_available(iommu_spec->np) )
+        return NO_IOMMU;
+
+    rc = iommu_fwspec_init(dev, &iommu_spec->np->dev);
+    if ( rc )
+        return rc;
+
+    /*
+     * Provide DT IOMMU specifier which describes the IOMMU master
+     * interfaces of that device (device IDs, etc) to the driver.
+     * The driver is responsible to decide how to interpret them.
+     */
+    return ops->dt_xlate(dev, iommu_spec);
+}
+
 int iommu_add_dt_device(struct dt_device_node *np)
 {
     const struct iommu_ops *ops = iommu_get_ops();
     struct dt_phandle_args iommu_spec;
     struct device *dev = dt_to_dev(np);
-    int rc = 1, index = 0;
+    int rc = NO_IOMMU, index = 0;
 
     if ( !iommu_enabled )
-        return 1;
+        return NO_IOMMU;
 
     if ( !ops )
         return -EINVAL;
@@ -163,22 +190,10 @@ int iommu_add_dt_device(struct dt_device_node *np)
          * The driver which supports generic IOMMU DT bindings must have
          * these callback implemented.
          */
-        if ( !ops->add_device || !ops->dt_xlate )
+        if ( !ops->add_device )
             return -EINVAL;
 
-        if ( !dt_device_is_available(iommu_spec.np) )
-            break;
-
-        rc = iommu_fwspec_init(dev, &iommu_spec.np->dev);
-        if ( rc )
-            break;
-
-        /*
-         * Provide DT IOMMU specifier which describes the IOMMU master
-         * interfaces of that device (device IDs, etc) to the driver.
-         * The driver is responsible to decide how to interpret them.
-         */
-        rc = ops->dt_xlate(dev, &iommu_spec);
+        rc = iommu_dt_xlate(dev, &iommu_spec);
         if ( rc )
             break;
 
-- 
2.40.1