drm/nouveau/acpi: ensure matching ACPI handle and supported functions

commit df42194a upstream.

Ensure that the returned set of supported DSM functions (MUX, Optimus)
match the ACPI handle that is set in nouveau_dsm_pci_probe.

As there are no machines with a MUX function on just one PCI device and
an Optimus on another, there should not be a functional impact. This
change however makes this implicit assumption more obvious.

Convert int to bool and rename has_dsm to has_mux while at it. Let the
caller set nouveau_dsm_priv.dhandle as needed.

 v2: pass dhandle to the caller.
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Acked-by: Dave Airlie <airlied@redhat.com
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/nouveau/nouveau_acpi.c

@@ -58,9 +58,6 @@ bool nouveau_is_v1_dsm(void) {
 	return nouveau_dsm_priv.dsm_detected;
 }
 
-#define NOUVEAU_DSM_HAS_MUX 0x1
-#define NOUVEAU_DSM_HAS_OPT 0x2
-
 #ifdef CONFIG_VGA_SWITCHEROO
 static const char nouveau_dsm_muid[] = {
 	0xA0, 0xA0, 0x95, 0x9D, 0x60, 0x00, 0x48, 0x4D,
@@ -213,27 +210,34 @@ static struct vga_switcheroo_handler nouveau_dsm_handler = {
 	.get_client_id = nouveau_dsm_get_client_id,
 };
 
-static int nouveau_dsm_pci_probe(struct pci_dev *pdev)
+static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out,
+				  bool *has_mux, bool *has_opt)
 {
 	acpi_handle dhandle;
-	int retval = 0;
+	bool supports_mux;
+	bool supports_opt;
 
 	dhandle = ACPI_HANDLE(&pdev->dev);
 	if (!dhandle)
-		return false;
+		return;
 
 	if (!acpi_has_method(dhandle, "_DSM")) {
 		nouveau_dsm_priv.other_handle = dhandle;
-		return false;
+		return;
 	}
-	if (acpi_check_dsm(dhandle, nouveau_dsm_muid, 0x00000102,
-			   1 << NOUVEAU_DSM_POWER))
-		retval |= NOUVEAU_DSM_HAS_MUX;
+	supports_mux = acpi_check_dsm(dhandle, nouveau_dsm_muid, 0x00000102,
+				      1 << NOUVEAU_DSM_POWER);
+	supports_opt = nouveau_check_optimus_dsm(dhandle);
 
-	if (nouveau_check_optimus_dsm(dhandle))
-		retval |= NOUVEAU_DSM_HAS_OPT;
+	/* Does not look like a Nvidia device. */
+	if (!supports_mux && !supports_opt)
+		return;
 
-	if (retval & NOUVEAU_DSM_HAS_OPT) {
+	*dhandle_out = dhandle;
+	*has_mux = supports_mux;
+	*has_opt = supports_opt;
+
+	if (supports_opt) {
 		uint32_t result;
 		nouveau_optimus_dsm(dhandle, NOUVEAU_DSM_OPTIMUS_CAPS, 0,
 				    &result);
@@ -242,10 +246,6 @@ static int nouveau_dsm_pci_probe(struct pci_dev *pdev)
 			 (result & OPTIMUS_DYNAMIC_PWR_CAP) ? "dynamic power, " : "",
 			 (result & OPTIMUS_HDA_CODEC_MASK) ? "hda bios codec supported" : "");
 	}
-	if (retval)
-		nouveau_dsm_priv.dhandle = dhandle;
-
-	return retval;
 }
 
 static bool nouveau_dsm_detect(void)
@@ -253,11 +253,11 @@ static bool nouveau_dsm_detect(void)
 	char acpi_method_name[255] = { 0 };
 	struct acpi_buffer buffer = {sizeof(acpi_method_name), acpi_method_name};
 	struct pci_dev *pdev = NULL;
-	int has_dsm = 0;
-	int has_optimus = 0;
+	acpi_handle dhandle = NULL;
+	bool has_mux = false;
+	bool has_optimus = false;
 	int vga_count = 0;
 	bool guid_valid;
-	int retval;
 	bool ret = false;
 
 	/* lookup the MXM GUID */
@@ -270,32 +270,26 @@ static bool nouveau_dsm_detect(void)
 	while ((pdev = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, pdev)) != NULL) {
 		vga_count++;
 
-		retval = nouveau_dsm_pci_probe(pdev);
-		if (retval & NOUVEAU_DSM_HAS_MUX)
-			has_dsm |= 1;
-		if (retval & NOUVEAU_DSM_HAS_OPT)
-			has_optimus = 1;
+		nouveau_dsm_pci_probe(pdev, &dhandle, &has_mux, &has_optimus);
 	}
 
 	while ((pdev = pci_get_class(PCI_CLASS_DISPLAY_3D << 8, pdev)) != NULL) {
 		vga_count++;
 
-		retval = nouveau_dsm_pci_probe(pdev);
-		if (retval & NOUVEAU_DSM_HAS_MUX)
-			has_dsm |= 1;
-		if (retval & NOUVEAU_DSM_HAS_OPT)
-			has_optimus = 1;
+		nouveau_dsm_pci_probe(pdev, &dhandle, &has_mux, &has_optimus);
 	}
 
 	/* find the optimus DSM or the old v1 DSM */
-	if (has_optimus == 1) {
+	if (has_optimus) {
+		nouveau_dsm_priv.dhandle = dhandle;
 		acpi_get_name(nouveau_dsm_priv.dhandle, ACPI_FULL_PATHNAME,
 			&buffer);
 		printk(KERN_INFO "VGA switcheroo: detected Optimus DSM method %s handle\n",
 			acpi_method_name);
 		nouveau_dsm_priv.optimus_detected = true;
 		ret = true;
-	} else if (vga_count == 2 && has_dsm && guid_valid) {
+	} else if (vga_count == 2 && has_mux && guid_valid) {
+		nouveau_dsm_priv.dhandle = dhandle;
 		acpi_get_name(nouveau_dsm_priv.dhandle, ACPI_FULL_PATHNAME,
 			&buffer);
 		printk(KERN_INFO "VGA switcheroo: detected DSM switching method %s handle\n",