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>
v4: Use MODULE_DEVICE_TABLE() (Thomas WeiÃ?schuh <thomas@xxxxxxxx>)
Fix scope of internal driver state; various style fixes (Barnabás
PÅ?cze, Andy Shevchenko)
Use devm_backlight_device_register() (Barnabás PÅ?cze)
Add kerneldoc comments for enums and structs (Andy Shevchenko)
MAINTAINERS | 6 +
drivers/platform/x86/Kconfig | 16 ++
drivers/platform/x86/Makefile | 1 +
drivers/platform/x86/wmaa-backlight-wmi.c | 185 ++++++++++++++++++++++
4 files changed, 208 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..0df908ef8d7c 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -113,6 +113,22 @@ 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 (EC).
+
+ Say Y or M here if you want to control the backlight on a notebook
+ system with an EC-driven backlight using the ACPI WMAA method.
+
+ If you choose to compile this driver as a module the module will be
+ called wmaa-backlight-wmi.
+
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..cb1a973803b1
--- /dev/null
+++ b/drivers/platform/x86/wmaa-backlight-wmi.c
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2020, NVIDIA CORPORATION. All rights reserved.
+ */
+
+#include <linux/backlight.h>
+#include <linux/module.h>
+#include <linux/wmi.h>
+
+/**
+ * enum wmaa_method - WMI method IDs for ACPI WMAA
+ *
+ * @WMAA_LEVEL: Get or set the brightness level,
+ * or get the maximum brightness level.
+ * @WMAA_SOURCE: Get the source for backlight control.
+ */
+enum wmaa_method {
+ WMAA_LEVEL = 1,
+ WMAA_SOURCE = 2,
+};
+
+/**
+ * enum wmaa_get_or_set - Operation mode for ACPI WMAA method
+ *
+ * @WMAA_GET: Get the current brightness level or backlight source.
+ * @WMAA_SET: Set the brightness level.
+ * @WMAA_GET_MAX: Get the maximum brightness level. This is only valid when the
+ * WMI method is %WMAA_LEVEL.
+ */
+enum wmaa_get_or_set {
+ WMAA_GET = 0,
+ WMAA_SET = 1,
+ WMAA_GET_MAX = 2
+};
+
+/**
+ * enum wmaa_source - Backlight brightness control source identification
+ *
+ * @WMAA_SOURCE_GPU: Backlight brightness is controlled by the GPU.
+ * @WMAA_SOURCE_EC: Backlight brightness is controlled by the system's
+ * Embedded Controller (EC).
+ * @WMAA_SOURCE_AUX: Backlight brightness is controlled over the DisplayPort
+ * AUX channel.
+ */
+enum wmaa_source {
+ WMAA_SOURCE_GPU = 1,
+ WMAA_SOURCE_EC = 2,
+ WMAA_SOURCE_AUX = 3
+};
+
+/**
+ * struct wmaa_args - arguments for the ACPI WMAA method
+ *
+ * @set: Pass in an &enum wmaa_get_or_set value to select between getting or
+ * setting a value.
+ * @val: In parameter for value to set when operating in %WMAA_SET mode. Not
+ * used in %WMAA_GET or %WMAA_GET_MAX mode.
+ * @ret: Out parameter returning retrieved value when operating in %WMAA_GET
+ * or %WMAA_GET_MAX mode. Not used in %WMAA_SET mode.
+ * @ignored: Padding; not used. The ACPI method expects a 24 byte params struct.
+ *
+ * This is the parameters structure for the ACPI WMAA method as wrapped by WMI.
+ * The value passed in to @val or returned by @ret will be a brightness value
+ * when the WMI method ID is %WMAA_LEVEL, or an &enum wmaa_source value when
+ * the WMI method ID is %WMAA_SOURCE.
+ */
+struct wmaa_args {
+ u32 set;
+ u32 val;
+ u32 ret;
+ u32 ignored[3];
+};
+
+static int wmi_call_wmaa(struct wmi_device *w, 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(w, 0, method, &buf, &buf);
+ if (ACPI_FAILURE(status)) {
+ dev_err(&w->dev, "ACPI WMAA failed with %s\n",
+ acpi_format_exception(status));
+ return -EIO;
+ }
+
+ if (set != WMAA_SET)
+ *val = args.ret;
+
+ return 0;
+}
+
+static int wmaa_backlight_update_status(struct backlight_device *bd)
+{
+ struct wmi_device *wdev = bl_get_data(bd);
+
+ return wmi_call_wmaa(wdev, WMAA_LEVEL, WMAA_SET, &bd->props.brightness);
+}
+
+static int wmaa_backlight_get_brightness(struct backlight_device *bd)
+{
+ struct wmi_device *wdev = bl_get_data(bd);
+ u32 level = 0;
+ int ret;
+
+ ret = wmi_call_wmaa(wdev, WMAA_LEVEL, WMAA_GET, &level);
+
+ if (ret)
+ dev_err(&bd->dev, "ACPI WMAA failed to get backlight level.\n");
+
+ return level;
+}
+
+static const struct backlight_ops wmaa_backlight_ops = {
+ .update_status = wmaa_backlight_update_status,
+ .get_brightness = wmaa_backlight_get_brightness
+};
+
+static int wmaa_backlight_wmi_probe(struct wmi_device *w, const void *ctx)
+{
+ struct backlight_properties props = {};
+ struct backlight_device *backlight;
+ u32 source;
+ int ret;
+
+ ret = wmi_call_wmaa(w, WMAA_SOURCE, WMAA_GET, &source);
+ if (ret)
+ return ret;
+
+ if (source != WMAA_SOURCE_EC) {
+ /* This driver is only to be used when brightness control is
+ * handled by the EC; otherwise, the GPU driver(s) should handle
+ * brightness control. */
+ return -ENODEV;
+ }
+
+ /* Identify this backlight device as a platform device so that it can
+ * be prioritized over any exposed GPU-driven raw device(s). */
+ props.type = BACKLIGHT_PLATFORM;
+
+ ret = wmi_call_wmaa(w, WMAA_LEVEL, WMAA_GET_MAX, &props.max_brightness);
+ if (ret)
+ return ret;
+
+ ret = wmi_call_wmaa(w, WMAA_LEVEL, WMAA_GET, &props.brightness);
+ if (ret)
+ return ret;
+
+ backlight = devm_backlight_device_register(
+ &w->dev, "wmaa_backlight",
+ &w->dev, w, &wmaa_backlight_ops, &props);
+ if (IS_ERR(backlight))
+ return PTR_ERR(backlight);
+
+ return 0;
+}
+
+#define WMAA_WMI_GUID "603E9613-EF25-4338-A3D0-C46177516DB7"
+
+static const struct wmi_device_id wmaa_backlight_wmi_id_table[] = {
+ { .guid_string = WMAA_WMI_GUID },
+ { }
+};
+MODULE_DEVICE_TABLE(wmi, wmaa_backlight_wmi_id_table);
+
+static struct wmi_driver wmaa_backlight_wmi_driver = {
+ .driver = {
+ .name = "wmaa-backlight"
+ },
+ .probe = wmaa_backlight_wmi_probe,
+ .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");
--
2.20.1
