platform: chrome: Add Tablet Switch ACPI driver

Add a kernel driver for GOOG0006, an ACPI driver reporting an event when
the tablet switch status changes.

On an ACPI based convertible chromebook check evtest display tablet mode
switch changes:
Available devices:
..
/dev/input/event3:      Tablet Mode Switch
..
Testing ... (interrupt to exit)
Event: time 1484879712.604360, type 5 (EV_SW), code 1 (SW_TABLET_MODE),
value 1
Event: time 1484879712.604360, -------------- SYN_REPORT ------------
Event: time 1484879715.132228, type 5 (EV_SW), code 1 (SW_TABLET_MODE),
value 0
Event: time 1484879715.132228, -------------- SYN_REPORT ------------
...
Check state is updated at resume time when different from suspend time.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Benson Leung <bleung@chromium.org>

3 files changed, 139 insertions, 0 deletions

diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
index e728a96cabfd..57aabe6e94a3 100644
--- a/drivers/platform/chrome/Kconfig
+++ b/drivers/platform/chrome/Kconfig
@@ -38,6 +38,16 @@ config CHROMEOS_PSTORE
           If you have a supported Chromebook, choose Y or M here.
           The module will be called chromeos_pstore.
 
+config CHROMEOS_TBMC
+        tristate "ChromeOS Tablet Switch Controller"
+        depends on ACPI
+        help
+          This option adds a driver for the tablet switch on
+          select Chrome OS systems.
+
+          To compile this driver as a module, choose M here: the
+          module will be called chromeos_tbmc.
+
 config CROS_EC_CTL
         tristate
 
diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index ff3b369911f0..e44c37a63fa9 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -2,6 +2,7 @@
 
 obj-$(CONFIG_CHROMEOS_LAPTOP)           += chromeos_laptop.o
 obj-$(CONFIG_CHROMEOS_PSTORE)           += chromeos_pstore.o
+obj-$(CONFIG_CHROMEOS_TBMC)             += chromeos_tbmc.o
 cros_ec_ctl-objs                        := cros_ec_sysfs.o cros_ec_lightbar.o \
                                            cros_ec_vbc.o cros_ec_debugfs.o
 obj-$(CONFIG_CROS_EC_CTL)               += cros_ec_ctl.o
diff --git a/drivers/platform/chrome/chromeos_tbmc.c b/drivers/platform/chrome/chromeos_tbmc.c
new file mode 100644
index 000000000000..c87e53319dae
--- /dev/null
+++ b/drivers/platform/chrome/chromeos_tbmc.c
@@ -0,0 +1,128 @@
+/*
+ * chromeos_tbmc - Driver to detect Tablet Mode for ChromeOS convertible.
+ *
+ * Copyright 2017 Google, Inc
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * On Chromebook using ACPI, this device listens for notification
+ * from GOOG0006 and issue method TBMC to retrieve the status.
+ *
+ * GOOG0006 issues the notification when it receives EC_HOST_EVENT_MODE_CHANGE
+ * from the EC.
+ * Method TBMC reads EC_ACPI_MEM_DEVICE_ORIENTATION byte from the shared
+ * memory region.
+ */
+
+#include <linux/acpi.h>
+#include <linux/input.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+
+#define DRV_NAME "chromeos_tbmc"
+#define ACPI_DRV_NAME "GOOG0006"
+
+static int chromeos_tbmc_query_switch(struct acpi_device *adev,
+                                     struct input_dev *idev)
+{
+        unsigned long long state;
+        acpi_status status;
+
+        status = acpi_evaluate_integer(adev->handle, "TBMC", NULL, &state);
+        if (ACPI_FAILURE(status))
+                return -ENODEV;
+
+        /* input layer checks if event is redundant */
+        input_report_switch(idev, SW_TABLET_MODE, state);
+        input_sync(idev);
+
+        return 0;
+}
+
+static __maybe_unused int chromeos_tbmc_resume(struct device *dev)
+{
+        struct acpi_device *adev = to_acpi_device(dev);
+
+        return chromeos_tbmc_query_switch(adev, adev->driver_data);
+}
+
+static void chromeos_tbmc_notify(struct acpi_device *adev, u32 event)
+{
+        switch (event) {
+        case 0x80:
+                chromeos_tbmc_query_switch(adev, adev->driver_data);
+                break;
+        default:
+                dev_err(&adev->dev, "Unexpected event: 0x%08X\n", event);
+        }
+}
+
+static int chromeos_tbmc_open(struct input_dev *idev)
+{
+        struct acpi_device *adev = input_get_drvdata(idev);
+
+        return chromeos_tbmc_query_switch(adev, idev);
+}
+
+static int chromeos_tbmc_add(struct acpi_device *adev)
+{
+        struct input_dev *idev;
+        struct device *dev = &adev->dev;
+        int ret;
+
+        idev = devm_input_allocate_device(dev);
+        if (!idev)
+                return -ENOMEM;
+
+        idev->name = "Tablet Mode Switch";
+        idev->phys = acpi_device_hid(adev);
+
+        idev->id.bustype = BUS_HOST;
+        idev->id.version = 1;
+        idev->id.product = 0;
+        idev->open = chromeos_tbmc_open;
+
+        input_set_drvdata(idev, adev);
+        adev->driver_data = idev;
+
+        input_set_capability(idev, EV_SW, SW_TABLET_MODE);
+        ret = input_register_device(idev);
+        if (ret) {
+                dev_err(dev, "cannot register input device\n");
+                return ret;
+        }
+        return 0;
+}
+
+static const struct acpi_device_id chromeos_tbmc_acpi_device_ids[] = {
+        { ACPI_DRV_NAME, 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(acpi, chromeos_tbmc_acpi_device_ids);
+
+static const SIMPLE_DEV_PM_OPS(chromeos_tbmc_pm_ops, NULL,
+                chromeos_tbmc_resume);
+
+static struct acpi_driver chromeos_tbmc_driver = {
+        .name = DRV_NAME,
+        .class = DRV_NAME,
+        .ids = chromeos_tbmc_acpi_device_ids,
+        .ops = {
+                .add = chromeos_tbmc_add,
+                .notify = chromeos_tbmc_notify,
+        },
+        .drv.pm = &chromeos_tbmc_pm_ops,
+};
+
+module_acpi_driver(chromeos_tbmc_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("ChromeOS ACPI tablet switch driver");