[PATCH V10 4/9] vfio: platform: add support for ACPI probe

Sinan Kaya
2016-07-18T23:09:22Z

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 <okaya@codeaurora.org>
---
drivers/vfio/platform/vfio_platform_common.c | 69 +++++++++++++++++++++++++--
drivers/vfio/platform/vfio_platform_private.h | 1 +
2 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
index 6be92c3..a5299f6 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 +50,32 @@ static vfio_platform_reset_fn_t vfio_platform_lookup_reset(const char *compat,
return reset_fn;
}

+static int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
+ struct device *dev)
+{
+ struct acpi_device *adev;
+
+ if (acpi_disabled)
+ return -EPERM;
+
+ adev = ACPI_COMPANION(dev);
+ if (!adev) {
+ pr_err("VFIO: ACPI companion device not found for %s\n",
+ vdev->name);
+ return -ENODEV;
+ }
+
+#ifdef CONFIG_ACPI
+ vdev->acpihid = acpi_device_hid(adev);
+ if (!vdev->acpihid) {
+ pr_err("VFIO: cannot find ACPI HID for %s\n",
+ vdev->name);
+ return -EINVAL;
+ }
+#endif
+ return WARN_ON(!vdev->acpihid) ? -ENOENT : 0;
+}
+
static bool vfio_platform_has_reset(struct vfio_platform_device *vdev)
{
return vdev->of_reset ? true : false;
@@ -547,6 +574,37 @@ 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;
+}
+
+/*
+ * There can be two kernel build combinations. One build where
+ * ACPI is not selected in Kconfig and another one with the ACPI Kconfig.
+ *
+ * In the first case, vfio_platform_acpi_probe will return since
+ * acpi_disabled is 1. DT user will not see any kind of messages from
+ * ACPI.
+ *
+ * In the second case, both DT and ACPI is compiled in but the system is
+ * booting with any of these combinations.
+ *
+ * If the firmware is DT type, then acpi_disabled is 1. The ACPI probe routine
+ * terminates immediately without any messages.
+ *
+ * If the firmware is ACPI type, then acpi_disabled is 0. All other checks are
+ * valid checks. We cannot claim that this system is DT.
+ */
int vfio_platform_probe_common(struct vfio_platform_device *vdev,
struct device *dev)
{
@@ -556,11 +614,12 @@ 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