Re: [PATCH] platform: chrome: Add Tablet Switch ACPI driver

[Benson Leung <bleung@google.com>]

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Hi Gwendal,

Thanks for sending this!

On Mon, Jan 23, 2017 at 03:39:55PM -0800, Gwendal Grignou wrote:
> 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 ------------
> ...
> 
> Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
> ---
>  drivers/platform/chrome/Kconfig         |  46 ++++++++-----
>  drivers/platform/chrome/Makefile        |   1 +
>  drivers/platform/chrome/chromeos_tbmc.c | 117 ++++++++++++++++++++++++++++++++
>  3 files changed, 146 insertions(+), 18 deletions(-)
>  create mode 100644 drivers/platform/chrome/chromeos_tbmc.c
> 
> diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
> index 76bdae1a93bb..51f8d7df4ad4 100644
> --- a/drivers/platform/chrome/Kconfig
> +++ b/drivers/platform/chrome/Kconfig
> @@ -38,31 +38,41 @@ 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_CHARDEV
> -        tristate "Chrome OS Embedded Controller userspace device interface"
> -        depends on MFD_CROS_EC
> -        ---help---
> -          This driver adds support to talk with the ChromeOS EC from userspace.
> +	tristate "Chrome OS Embedded Controller userspace device interface"
> +	depends on MFD_CROS_EC
> +	---help---
> +	  This driver adds support to talk with the ChromeOS EC from userspace.
>  
> -          If you have a supported Chromebook, choose Y or M here.
> -          The module will be called cros_ec_dev.
> +	  If you have a supported Chromebook, choose Y or M here.
> +	  The module will be called cros_ec_dev.
>  
>  config CROS_EC_LPC
> -        tristate "ChromeOS Embedded Controller (LPC)"
> -        depends on MFD_CROS_EC && (X86 || COMPILE_TEST)
> -        help
> -          If you say Y here, you get support for talking to the ChromeOS EC
> -          over an LPC bus. This uses a simple byte-level protocol with a
> -          checksum. This is used for userspace access only. The kernel
> -          typically has its own communication methods.
> +	tristate "ChromeOS Embedded Controller (LPC)"
> +	depends on MFD_CROS_EC && (X86 || COMPILE_TEST)
> +	help
> +	  If you say Y here, you get support for talking to the ChromeOS EC
> +	  over an LPC bus. This uses a simple byte-level protocol with a
> +	  checksum. This is used for userspace access only. The kernel
> +	  typically has its own communication methods.
>  
> -          To compile this driver as a module, choose M here: the
> -          module will be called cros_ec_lpc.
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called cros_ec_lpc.
>  
>  config CROS_EC_PROTO
> -        bool
> -        help
> -          ChromeOS EC communication protocol helpers.
> +	bool
> +	help
> +	  ChromeOS EC communication protocol helpers.
>  

Let's leave the cleanup of the Kconfig (for whitespace) for another patch.
Just add the CHROMEOS_TBMC.

>  config CROS_KBD_LED_BACKLIGHT
>  	tristate "Backlight LED support for Chrome OS keyboards"
> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
> index 4f3462783a3c..b61a0166c0ce 100644
> --- a/drivers/platform/chrome/Makefile
> +++ b/drivers/platform/chrome/Makefile
> @@ -1,6 +1,7 @@
>  
>  obj-$(CONFIG_CHROMEOS_LAPTOP)		+= chromeos_laptop.o
>  obj-$(CONFIG_CHROMEOS_PSTORE)		+= chromeos_pstore.o
> +obj-$(CONFIG_CHROMEOS_TBMC)		+= chromeos_tbmc.o
>  cros_ec_devs-objs			:= cros_ec_dev.o cros_ec_sysfs.o \
>  					   cros_ec_lightbar.o cros_ec_vbc.o
>  obj-$(CONFIG_CROS_EC_CHARDEV)		+= cros_ec_devs.o
> diff --git a/drivers/platform/chrome/chromeos_tbmc.c b/drivers/platform/chrome/chromeos_tbmc.c
> new file mode 100644
> index 000000000000..c159eb38d79b
> --- /dev/null
> +++ b/drivers/platform/chrome/chromeos_tbmc.c
> @@ -0,0 +1,117 @@
> +/*
> + * 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 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 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,
> +	},
> +};

I talked to you about this offline, but can you check if you do or do not
need special resume handling of this switch? I suspect there's a
decent chance the notify might not result in an event if the tablet
mode changed during the time the Chromebook is sleeping.

Thanks!
Benson

-- 
Benson Leung
Senior Software Engineer
Chrome OS Kernel
Google Inc.
bleung@google.com
Chromium OS Project
bleung@chromium.org

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