[Intel-gfx] RFC] [Patch] [DRM/I915] :Check the LID device to decide whether the LVDS should be initialized

[yakui_zhao]

Hi, All

    This is a patch that the LID device is checked to decide whether the LVDS should
be initialized. If there is no LID device, it won't initialize the LVDS output device
in KMS mode on the boxes based on intel mobile chipset. In such case the pipe occupied
by LVDS can be used for other output device.
    If the LID device can be found, it will continue the current flowchart.
    
    On some boxes the mobile chipset is used and there is no LVDS device. In such
case we had better not initialize the LVDS output device so that one pipe can
be used for other output device. For example: E-TOP in bug 21496

But unfortunately the LVDS device is still initialized on such boxes based on
mobile chipset in KMS mode. It brings that this pipe occupied by LVDS can't be
used for other output device.

After checking the acpidump we find that there is no LID device on such boxes.
In such case we can use the LID device to decide whether the LVDS device should
be initialized. 

If there is no LID device, we can think that there is no LVDS device. It is
unnecessary to initialize the LVDS output device.
If there exists the LID device, it will continue the current flowchart.

Maybe on some boxes there is no LVDS device but the LID device is found. In
such case it had better be added to the quirk table.

Welcome the comments.
   Yakui
---
 drivers/gpu/drm/i915/intel_lvds.c |   79 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

Index: linux-2.6/drivers/gpu/drm/i915/intel_lvds.c
===================================================================
--- linux-2.6.orig/drivers/gpu/drm/i915/intel_lvds.c	2009-06-11 15:27:07.000000000 +0800
+++ linux-2.6/drivers/gpu/drm/i915/intel_lvds.c	2009-06-11 17:42:07.000000000 +0800
@@ -36,6 +36,7 @@
 #include "intel_drv.h"
 #include "i915_drm.h"
 #include "i915_drv.h"
+#include <linux/acpi.h>
 
 /**
  * Sets the backlight level.
@@ -503,7 +504,74 @@
 
 	{ }	/* terminating entry */
 };
+#ifdef CONFIG_ACPI
+/*
+ * check_lid_device -- check whether it is ACPI LID device.
+ * @handle: ACPI device handle
+ * @level : depth in the ACPI namespace tree
+ * @context: the number of LID device when we find the device
+ * @rv: a return value to fill if desired (Not use)
+ *
+ * check whether it is a LID device by comparing the HID. If it is,
+ * increase the number of LID device.
+ */
+static acpi_status
+check_lid_device(acpi_handle handle, u32 level, void *context,
+			void **retyurn_value)
+{
+#define		ACPI_HID_LID		"PNP0C0D"
+	struct acpi_device *acpi_dev;
+	int *p_lid = (int *)context;
+
+	acpi_dev = NULL;
+	/* Get the acpi device for device handle */
+	if (acpi_bus_get_device(handle, &acpi_dev) || !acpi_dev) {
+		/* If there is no ACPI device for handle, return */
+		return AE_OK;
+	}
+	if (!strncmp(acpi_device_hid(acpi_dev), ACPI_HID_LID, 7)) {
+		/*
+		 * compare the device HID with "PNP0C0D". If it is equal, the
+		 * LID device is found. Increase the count
+		 */
+		(*p_lid)++;
+	}
+	return AE_OK;
+}
+/**
+ * check whether there exists the ACPI LID device by enumerating the ACPI
+ * device tree.
+ * If ACPI is disabled, there is no ACPI device tree. 0 is returned.
+ * If the LID device is found, it will return zero.
+ * If no LID device is found, it will return  -ENODEV.
+ */
+static int intel_lvds_find_lid(void)
+{
+	int lid_count = 0;
 
+	if (acpi_disabled) {
+		/*
+		 * if ACPI is disabled, there is no ACPI device tree. And
+		 * we don't know whether there exists the LID device.
+		 * In such case we will return 0.
+		 */
+		return 0;
+	}
+
+	acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
+				ACPI_UINT32_MAX,
+				check_lid_device, &lid_count, NULL);
+
+	if (!lid_count) {
+		/* No LID device is not found. Return -ENODEV */
+		return -ENODEV;
+	}
+
+	return 0;
+}
+#else
+static inline int intel_lvds_find_lid(void) { return 0; }
+#endif
 /**
  * intel_lvds_init - setup LVDS connectors on this device
  * @dev: drm device
@@ -526,6 +594,17 @@
 	if (dmi_check_system(intel_no_lvds))
 		return;
 
+	if (intel_lvds_find_lid()) {
+		/* If there is no LID device, we can think that there is
+		 * no LVDS output device. In such case it is unnecessary to
+		 * create the LVDS output device.
+		 * But maybe on some boxes there is no LVDS device while the
+		 * LID device is found. If so, it had better be added to
+		 * the quirk list.
+		 */
+		return;
+	}
+
 	if (IS_IGDNG(dev)) {
 		if ((I915_READ(PCH_LVDS) & LVDS_DETECTED) == 0)
 			return;