On 2016-07-18 20:00, Alex Williamson wrote:

On Mon, 18 Jul 2016 19:09:22 -0400
Sinan Kaya [off-list ref] wrote:

quoted

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 <redacted>
---
 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);

I didn't necessarily have a problem with this being set in the
declaration.

I think this is better. If ACPI is disabled, it is dangerous to call an 
ACPI API.

quoted

+	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;

?!?!  The point was that that entire if{} branch is unnecessary.  The
WARN_ON handles the (impossible) case of !vdev->acpihid.  We just need:

#ifdef CONFIG_ACPI
	vdev->acpihid = acpi_device_hid(adev);
#endif
	return WARN_ON(!vdev->acpihid) ? -ENOENT : 0;

OK, got it now. I thought you were trying to get rid of #else

nit, might make sense to replace EPERM with ENOENT and use EINVAL here.

Sure, will take carr of it.

Anything else I need to take care of?

quoted

+}
+
 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;