[PATCH V5 4/6] vfio: platform: add support for ACPI probe

[Sinan Kaya]

The code is using the compatible DT string to associate a reset driver
with the actual device itself. The compatible string does not exist on
ACPI based systems. HID is the unique identifier for a device driver
instead.

Signed-off-by: Sinan Kaya <ok...@codeaurora.org>
---
 drivers/vfio/platform/vfio_platform_common.c  | 58 ++++++++++++++++++++++++---
 drivers/vfio/platform/vfio_platform_private.h |  1 +
 2 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/platform/vfio_platform_common.c 
b/drivers/vfio/platform/vfio_platform_common.c
index 25378bd..d859d3b 100644
--- a/drivers/vfio/platform/vfio_platform_common.c
+++ b/drivers/vfio/platform/vfio_platform_common.c
@@ -13,6 +13,7 @@
  */
 
 #include <linux/device.h>
+#include <linux/acpi.h>
 #include <linux/iommu.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
@@ -49,6 +50,37 @@ static vfio_platform_reset_fn_t 
vfio_platform_lookup_reset(const char *compat,
        return reset_fn;
 }
 
+#ifdef CONFIG_ACPI
+int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
+                            struct device *dev)
+{
+       struct acpi_device *adev = ACPI_COMPANION(dev);
+
+       if (acpi_disabled)
+               return -ENODEV;
+
+       if (!adev) {
+               pr_err("VFIO: ACPI companion device not found for %s\n",
+                       vdev->name);
+               return -ENODEV;
+       }
+
+       vdev->acpihid = acpi_device_hid(adev);
+       if (!vdev->acpihid) {
+               pr_err("VFIO: cannot find ACPI HID for %s\n",
+                      vdev->name);
+               return -ENODEV;
+       }
+       return 0;
+}
+#else
+int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
+                            struct device *dev)
+{
+       return -EINVAL;
+}
+#endif
+
 static bool vfio_platform_has_reset(struct vfio_platform_device *vdev)
 {
        return vdev->of_reset ? true : false;
@@ -548,6 +580,21 @@ static const struct vfio_device_ops vfio_platform_ops = {
        .mmap           = vfio_platform_mmap,
 };
 
+int vfio_platform_of_probe(struct vfio_platform_device *vdev,
+                          struct device *dev)
+{
+       int ret;
+
+       ret = device_property_read_string(dev, "compatible",
+                                         &vdev->compat);
+       if (ret) {
+               pr_err("VFIO: cannot retrieve compat for %s\n",
+                       vdev->name);
+               return ret;
+       }
+       return 0;
+}
+
 int vfio_platform_probe_common(struct vfio_platform_device *vdev,
                               struct device *dev)
 {
@@ -557,11 +604,12 @@ int vfio_platform_probe_common(struct 
vfio_platform_device *vdev,
        if (!vdev)
                return -EINVAL;
 
-       ret = device_property_read_string(dev, "compatible", &vdev->compat);
-       if (ret) {
-               pr_err("VFIO: cannot retrieve compat for %s\n", vdev->name);
-               return -EINVAL;
-       }
+       ret = vfio_platform_acpi_probe(vdev, dev);
+       if (ret)
+               ret = vfio_platform_of_probe(vdev, dev);
+
+       if (ret)
+               return ret;
 
        vdev->device = dev;
 
diff --git a/drivers/vfio/platform/vfio_platform_private.h 
b/drivers/vfio/platform/vfio_platform_private.h
index 71ed7d1..ba9e4f8 100644
--- a/drivers/vfio/platform/vfio_platform_private.h
+++ b/drivers/vfio/platform/vfio_platform_private.h
@@ -58,6 +58,7 @@ struct vfio_platform_device {
        struct mutex                    igate;
        struct module                   *parent_module;
        const char                      *compat;
+       const char                      *acpihid;
        struct module                   *reset_module;
        struct device                   *device;
 
-- 
1.8.2.1