A number of upcoming notebook computer designs drive the internal
display panel's backlight PWM through the Embedded Controller (EC).
This EC-based backlight control can be plumbed through to an ACPI
"WMAA" method interface, which in turn can be wrapped by WMI with
the GUID handle 603E9613-EF25-4338-A3D0-C46177516DB7.
Add a new driver, aliased to the WMAA WMI GUID, to expose a sysfs
backlight class driver to control backlight levels on systems with
EC-driven backlights.
Signed-off-by: Aaron Plattner <aplattner@xxxxxxxxxx>
Signed-off-by: Daniel Dadap <ddadap@xxxxxxxxxx>
---
v2: Convert to WMI subsystem driver, suggested by Mario Limonciello
<mario.limonciello@xxxxxxxxxxx>; various cleanups suggested by
Barnabás PÅ?cze <pobrn@xxxxxxxxxxxxxx>
v3: Address assorted style nits raised by Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> in response to a related patch; remove
additional behavior change to WMI subsystem from patch series as
recommended by Hans de Goede <hdegoede@xxxxxxxxxx>
MAINTAINERS | 6 +
drivers/platform/x86/Kconfig | 10 ++
drivers/platform/x86/Makefile | 1 +
drivers/platform/x86/wmaa-backlight-wmi.c | 184 ++++++++++++++++++++++
4 files changed, 201 insertions(+)
create mode 100644 drivers/platform/x86/wmaa-backlight-wmi.c
diff --git a/MAINTAINERS b/MAINTAINERS
index bbaecde94aa0..fd7362a86c6d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20008,6 +20008,12 @@ L: linux-wireless@xxxxxxxxxxxxxxx
S: Odd fixes
F: drivers/net/wireless/wl3501*
+WMAA BACKLIGHT DRIVER
+M: Daniel Dadap <ddadap@xxxxxxxxxx>
+L: platform-driver-x86@xxxxxxxxxxxxxxx
+S: Supported
+F: drivers/platform/x86/wmaa-backlight-wmi.c
+
WOLFSON MICROELECTRONICS DRIVERS
L: patches@xxxxxxxxxxxxxxxxxxxxx
S: Supported
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index d12db6c316ea..e54449c16d03 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -113,6 +113,16 @@ config PEAQ_WMI
help
Say Y here if you want to support WMI-based hotkeys on PEAQ 2-in-1s.
+config WMAA_BACKLIGHT_WMI
+ tristate "ACPI WMAA Backlight Driver"
+ depends on ACPI_WMI
+ depends on BACKLIGHT_CLASS_DEVICE
+ help
+ This driver provides a sysfs backlight interface for notebook
+ systems which expose the WMAA ACPI method and an associated WMI
+ wrapper to drive LCD backlight levels through the system's
+ Embedded Controller.
+
config XIAOMI_WMI
tristate "Xiaomi WMI key driver"
depends on ACPI_WMI
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index 7ee369aab10d..109c1714237d 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_INTEL_WMI_SBL_FW_UPDATE) += intel-wmi-sbl-fw-update.o
obj-$(CONFIG_INTEL_WMI_THUNDERBOLT) += intel-wmi-thunderbolt.o
obj-$(CONFIG_MXM_WMI) += mxm-wmi.o
obj-$(CONFIG_PEAQ_WMI) += peaq-wmi.o
+obj-$(CONFIG_WMAA_BACKLIGHT_WMI) += wmaa-backlight-wmi.o
obj-$(CONFIG_XIAOMI_WMI) += xiaomi-wmi.o
obj-$(CONFIG_GIGABYTE_WMI) += gigabyte-wmi.o
diff --git a/drivers/platform/x86/wmaa-backlight-wmi.c b/drivers/platform/x86/wmaa-backlight-wmi.c
new file mode 100644
index 000000000000..b607d3f88fc2
--- /dev/null
+++ b/drivers/platform/x86/wmaa-backlight-wmi.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2020, NVIDIA CORPORATION. All rights reserved.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/backlight.h>
+#include <linux/module.h>
+#include <linux/wmi.h>
+
+#define WMAA_WMI_GUID "603E9613-EF25-4338-A3D0-C46177516DB7"
+
+struct wmi_wmaa_priv {
+ struct backlight_device *backlight;
+};
+
+enum wmaa_method {
+ WMAA_BRIGHTNESS_LEVEL = 1,
+ WMAA_BRIGHTNESS_SOURCE = 2,
+};
+
+enum wmaa_get_or_set {
+ WMAA_GET = 0,
+ WMAA_SET = 1,
+ WMAA_GET_MAX = 2, // for WMAA_BRIGHTNESS_LEVEL only
+};
+
+enum wmaa_source {
+ WMAA_SOURCE_CLEAR = 0,
+ WMAA_SOURCE_GPU = 1,
+ WMAA_SOURCE_EC = 2,
+ WMAA_SOURCE_AUX = 3,
+ WMAA_SOURCE_COUNT
+};
+
+struct wmaa_args {
+ u32 set;
+ u32 val;
+ u32 ret;
+ u32 ignored[3];
+};
+
+static const struct wmi_device_id wmaa_backlight_wmi_id_table[] = {
+ { .guid_string = WMAA_WMI_GUID },
+ { },
+};
+
+static struct wmi_device *wdev;
+
+static int wmi_call_wmaa(enum wmaa_method method, enum wmaa_get_or_set set, u32 *val)
+{
+ struct wmaa_args args = {
+ .set = set,
+ .val = 0,
+ .ret = 0,
+ };
+ struct acpi_buffer buf = { (acpi_size)sizeof(args), &args };
+ acpi_status status;
+
+ if (set == WMAA_SET)
+ args.val = *val;
+
+ status = wmidev_evaluate_method(wdev, 0, method, &buf, &buf);
+ if (ACPI_FAILURE(status)) {
+ pr_err("ACPI WMAA failed with %s\n", acpi_format_exception(status));
+ return -EIO;
+ }
+
+ if (set != WMAA_SET)
+ *val = args.ret;
+
+ return 0;
+}
+
+static int wmaa_get_brightness(u32 *level)
+{
+ return wmi_call_wmaa(WMAA_BRIGHTNESS_LEVEL, WMAA_GET, level);
+}
+
+static int wmaa_set_brightness(u32 level)
+{
+ return wmi_call_wmaa(WMAA_BRIGHTNESS_LEVEL, WMAA_SET, &level);
+}
+
+static int wmaa_backlight_update_status(struct backlight_device *bd)
+{
+ return wmaa_set_brightness(bd->props.brightness);
+}
+
+static int wmaa_backlight_get_brightness(struct backlight_device *bd)
+{
+ u32 level;
+ int ret;
+
+ ret = wmaa_get_brightness(&level);
+
+ WARN_ON(ret != 0);
+ return ret == 0 ? level : 0;
+}
+
+static const struct backlight_ops wmaa_backlight_ops = {
+ .update_status = wmaa_backlight_update_status,
+ .get_brightness = wmaa_backlight_get_brightness,
+};
+
+static int wmaa_get_max_brightness(u32 *level)
+{
+ return wmi_call_wmaa(WMAA_BRIGHTNESS_LEVEL, WMAA_GET_MAX, level);
+}
+
+static int wmaa_get_brightness_source(u32 *source)
+{
+ return wmi_call_wmaa(WMAA_BRIGHTNESS_SOURCE, WMAA_GET, source);
+}
+
+static int wmaa_backlight_wmi_probe(struct wmi_device *w, const void *ctx)
+{
+ struct backlight_properties props = {0};
+ struct wmi_wmaa_priv *priv;
+ u32 source;
+ int ret;
+
+ priv = devm_kmalloc(&w->dev, sizeof(*priv), GFP_KERNEL);
+ if(!priv)
+ return -ENOMEM;
+
+ wdev = w;
+
+ ret = wmaa_get_brightness_source(&source);
+ if (ret)
+ goto done;
+
+ if (source != WMAA_SOURCE_EC) {
+ ret = -ENODEV;
+ goto done;
+ }
+
+ // Register a backlight handler
+ props.type = BACKLIGHT_PLATFORM;
+ ret = wmaa_get_max_brightness(&props.max_brightness);
+ if (ret)
+ goto done;
+
+ ret = wmaa_get_brightness(&props.brightness);
+ if (ret)
+ goto done;
+
+ priv->backlight = backlight_device_register("wmaa_backlight",
+ NULL, NULL, &wmaa_backlight_ops, &props);
+ if (IS_ERR(priv->backlight))
+ return PTR_ERR(priv->backlight);
+
+ dev_set_drvdata(&w->dev, priv);
+
+done:
+ return ret;
+}
+
+static void wmaa_backlight_wmi_remove(struct wmi_device *wdev)
+{
+ struct wmi_wmaa_priv *priv = dev_get_drvdata(&wdev->dev);
+
+ backlight_device_unregister(priv->backlight);
+}
+
+static struct wmi_driver wmaa_backlight_wmi_driver = {
+ .driver = {
+ .name = "wmaa-backlight",
+ },
+ .probe = wmaa_backlight_wmi_probe,
+ .remove = wmaa_backlight_wmi_remove,
+ .id_table = wmaa_backlight_wmi_id_table,
+};
+
+module_wmi_driver(wmaa_backlight_wmi_driver);
+
+MODULE_AUTHOR("Aaron Plattner <aplattner@xxxxxxxxxx>");
+MODULE_AUTHOR("Daniel Dadap <ddadap@xxxxxxxxxx>");
+MODULE_DESCRIPTION("WMAA Backlight WMI driver");
+MODULE_LICENSE("GPL v2");
+
+MODULE_ALIAS("wmi:"WMAA_WMI_GUID);
--
2.20.1
