1 files changed, 84 insertions, 2 deletions

diff --git a/include/linux/apple-gmux.h b/include/linux/apple-gmux.h
index 80efaaf89e07..1f68b49bcd68 100644
--- a/include/linux/apple-gmux.h
+++ b/include/linux/apple-gmux.h
@@ -8,6 +8,8 @@
 #define LINUX_APPLE_GMUX_H
 
 #include <linux/acpi.h>
+#include <linux/io.h>
+#include <linux/pnp.h>
 
 #define GMUX_ACPI_HID "APP000B"
 
@@ -35,14 +37,89 @@
 #define GMUX_MIN_IO_LEN			(GMUX_PORT_BRIGHTNESS + 4)
 
 #if IS_ENABLED(CONFIG_APPLE_GMUX)
+static inline bool apple_gmux_is_indexed(unsigned long iostart)
+{
+	u16 val;
+
+	outb(0xaa, iostart + 0xcc);
+	outb(0x55, iostart + 0xcd);
+	outb(0x00, iostart + 0xce);
+
+	val = inb(iostart + 0xcc) | (inb(iostart + 0xcd) << 8);
+	if (val == 0x55aa)
+		return true;
+
+	return false;
+}
 
 /**
- * apple_gmux_present() - detect if gmux is built into the machine
+ * apple_gmux_detect() - detect if gmux is built into the machine
+ *
+ * @pnp_dev:     Device to probe or NULL to use the first matching device
+ * @indexed_ret: Returns (by reference) if the gmux is indexed or not
+ *
+ * Detect if a supported gmux device is present by actually probing it.
+ * This avoids the false positives returned on some models by
+ * apple_gmux_present().
+ *
+ * Return: %true if a supported gmux ACPI device is detected and the kernel
+ * was configured with CONFIG_APPLE_GMUX, %false otherwise.
+ */
+static inline bool apple_gmux_detect(struct pnp_dev *pnp_dev, bool *indexed_ret)
+{
+	u8 ver_major, ver_minor, ver_release;
+	struct device *dev = NULL;
+	struct acpi_device *adev;
+	struct resource *res;
+	bool indexed = false;
+	bool ret = false;
+
+	if (!pnp_dev) {
+		adev = acpi_dev_get_first_match_dev(GMUX_ACPI_HID, NULL, -1);
+		if (!adev)
+			return false;
+
+		dev = get_device(acpi_get_first_physical_node(adev));
+		acpi_dev_put(adev);
+		if (!dev)
+			return false;
+
+		pnp_dev = to_pnp_dev(dev);
+	}
+
+	res = pnp_get_resource(pnp_dev, IORESOURCE_IO, 0);
+	if (!res || resource_size(res) < GMUX_MIN_IO_LEN)
+		goto out;
+
+	/*
+	 * Invalid version information may indicate either that the gmux
+	 * device isn't present or that it's a new one that uses indexed io.
+	 */
+	ver_major = inb(res->start + GMUX_PORT_VERSION_MAJOR);
+	ver_minor = inb(res->start + GMUX_PORT_VERSION_MINOR);
+	ver_release = inb(res->start + GMUX_PORT_VERSION_RELEASE);
+	if (ver_major == 0xff && ver_minor == 0xff && ver_release == 0xff) {
+		indexed = apple_gmux_is_indexed(res->start);
+		if (!indexed)
+			goto out;
+	}
+
+	if (indexed_ret)
+		*indexed_ret = indexed;
+
+	ret = true;
+out:
+	put_device(dev);
+	return ret;
+}
+
+/**
+ * apple_gmux_present() - check if gmux ACPI device is present
  *
  * Drivers may use this to activate quirks specific to dual GPU MacBook Pros
  * and Mac Pros, e.g. for deferred probing, runtime pm and backlight.
  *
- * Return: %true if gmux is present and the kernel was configured
+ * Return: %true if gmux ACPI device is present and the kernel was configured
  * with CONFIG_APPLE_GMUX, %false otherwise.
  */
 static inline bool apple_gmux_present(void)
@@ -57,6 +134,11 @@ static inline bool apple_gmux_present(void)
 	return false;
 }
 
+static inline bool apple_gmux_detect(struct pnp_dev *pnp_dev, bool *indexed_ret)
+{
+	return false;
+}
+
 #endif /* !CONFIG_APPLE_GMUX */
 
 #endif /* LINUX_APPLE_GMUX_H */