Some ThinkPad systems have a power-saving feature that turns off HDMI
audio device in Windows, but NVidia Linux driver does not support this
feature. As a result, HDMI audio will not work on Linux.
A BIOS workaround is added with an OEM_OSI string
"Linux-Lenovo-NV-HDMI-Audio" to power on NVidia HDMI audio when booting.
The form of the OEM _OSI strings is defined by each OEMs and is
discussed in Documentation/acpi/osi.txt.
Signed-off-by: Alex Hung <alex.hung@xxxxxxxxxxxxx>
---
drivers/acpi/osi.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/acpi/osi.c b/drivers/acpi/osi.c
index 8a8f435..b2a16ed 100644
--- a/drivers/acpi/osi.c
+++ b/drivers/acpi/osi.c
@@ -66,6 +66,14 @@ osi_setup_entries[OSI_STRING_ENTRIES_MAX] __initdata = {
* be removed if both new and old graphics cards are supported.
*/
{"Linux-Dell-Video", true},
+ /*
+ * Linux-Lenovo-NV-HDMI-Audio is used by BIOS to power on NVidia's HDMI
+ * audio device which is turned off for power-saving in Windows OS.
+ * This power management feature observed on some Lenovo Thinkpad
+ * systems which will not be able to output audio via HDMI without
+ * a BIOS workaround.
+ */
+ {"Linux-Lenovo-NV-HDMI-Audio", true},
};
static u32 acpi_osi_handler(acpi_string interface, u32 supported)
--
2.7.4
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
