[PATCH v6 1/3] PCI/ACPI: add a helper for retrieving _OSC Control DWORDs

[Vishal Verma <vishal.l.verma@intel.com>]

During _OSC negotiation, when the 'Control' DWORD is needed from the
result buffer after running _OSC, a couple of places performed manual
pointer arithmetic to offset into the right spot in the raw buffer.
Add a acpi_osc_ctx_get_pci_control() helper to use the #define'd
DWORD offsets to fetch the DWORDs needed from @acpi_osc_context, and
replace the above instances of the open-coded arithmetic.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Suggested-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 include/linux/acpi.h    | 13 +++++++++++++
 drivers/acpi/bus.c      |  2 +-
 drivers/acpi/pci_root.c |  2 +-
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 6274758648e3..ff4d1fdd9009 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -607,6 +607,13 @@ extern u32 osc_sb_native_usb4_control;
 #define OSC_PCI_EXPRESS_LTR_CONTROL		0x00000020
 #define OSC_PCI_EXPRESS_DPC_CONTROL		0x00000080
 
+static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
+{
+	u32 *ret = context->ret.pointer;
+
+	return ret[OSC_CONTROL_DWORD];
+}
+
 #define ACPI_GSB_ACCESS_ATTRIB_QUICK		0x00000002
 #define ACPI_GSB_ACCESS_ATTRIB_SEND_RCV         0x00000004
 #define ACPI_GSB_ACCESS_ATTRIB_BYTE		0x00000006
@@ -1003,6 +1010,12 @@ static inline int acpi_register_wakeup_handler(int wake_irq,
 static inline void acpi_unregister_wakeup_handler(
 	bool (*wakeup)(void *context), void *context) { }
 
+struct acpi_osc_context;
+static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
+{
+	return 0;
+}
+
 #endif	/* !CONFIG_ACPI */
 
 #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index 07f604832fd6..4992e05cf429 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -405,7 +405,7 @@ static void acpi_bus_osc_negotiate_usb_control(void)
 	}
 
 	osc_sb_native_usb4_control =
-		control & ((u32 *)context.ret.pointer)[OSC_CONTROL_DWORD];
+		control &  acpi_osc_ctx_get_pci_control(&context);
 
 	acpi_bus_decode_usb_osc("USB4 _OSC: OS supports", control);
 	acpi_bus_decode_usb_osc("USB4 _OSC: OS controls",
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index b76db99cced3..40a74ff3fa02 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -185,7 +185,7 @@ static acpi_status acpi_pci_run_osc(acpi_handle handle,
 
 	status = acpi_run_osc(handle, &context);
 	if (ACPI_SUCCESS(status)) {
-		*retval = *((u32 *)(context.ret.pointer + 8));
+		*retval = acpi_osc_ctx_get_pci_control(&context);
 		kfree(context.ret.pointer);
 	}
 	return status;
-- 
2.35.1