REJECTED/UNAPPLIED: [PATCH v2 1/1][SRU][Bionic][OEM-B]UBUNTU: SAUCE: platform/x86: dell-uart-backlight: new backlight driver for DELL AIO

Stefan Bader stefan.bader at canonical.com
Thu Aug 2 12:52:14 UTC 2018


On 17.07.2018 09:13, AceLan Kao wrote:
> BugLink: https://bugs.launchpad.net/bugs/1727235

The driver, as sent, does not compile. Also there are some warnings *see below(
which do not increase my confidence in the code. Before you re-submit, adding
new config options also requires a change in the Ubuntu config, setting the
desired mode (preferably built as module).

-Stefan

> 
> The Dell AIO machines released after 2017 come with a UART interface
> to communicate with the backlight scalar board. This driver creates
> a standard backlight interface and talks to the scalar board through
> UART.
> 
> In DSDT this uart port will be defined as
>    Name (_HID, "DELL0501")
>    Name (_CID, EisaId ("PNP0501")
> The 8250 PNP driver will be loaded by default, and this driver uses
> "DELL0501" to confirm the uart port is a backlight interface and
> leverage the port created by 8250 PNP driver to communicate with
> the scalar board.
> 
> v2:
>    1. move struct uart_cmd to .c file
>    2. make dell_uart_get_bl_power() inline
>    3. add space to ternary operator "bl_cmd->cmd[2] = power ? 0 : 1;"
>    4. check return value of kzalloc()
>    5. add kzfree()
>    6. check return value of backlight_device_register()
>    7. check return value of filp_open() at init
> 
> Signed-off-by: AceLan Kao <acelan.kao at canonical.com>
> ---
>  drivers/platform/x86/Kconfig               |  14 +
>  drivers/platform/x86/Makefile              |   1 +
>  drivers/platform/x86/dell-uart-backlight.c | 463 +++++++++++++++++++++
>  drivers/platform/x86/dell-uart-backlight.h |  35 ++
>  4 files changed, 513 insertions(+)
>  create mode 100644 drivers/platform/x86/dell-uart-backlight.c
>  create mode 100644 drivers/platform/x86/dell-uart-backlight.h
> 
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 683a875f3b6c..6edfa935a434 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -199,6 +199,20 @@ config DELL_RBTN
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called dell-rbtn.
>  
> +config DELL_UART_BACKLIGHT
> +	tristate "Dell AIO UART Backlight driver"
> +	depends on SERIAL_8250
> +	depends on ACPI
> +	---help---
> +	  Say Y here if you want to support Dell AIO UART backlight interface.
> +	  The Dell AIO machines released after 2017 come with a UART interface
> +	  to communicate with the backlight scalar board. This driver creates
> +	  a standard backlight interface and talks to the scalar board through
> +	  UART to adjust the AIO screen brightness.
> +
> +	  To compile this driver as a module, choose M here: the module will
> +	  be called dell_uart_backlight.
> +
>  
>  config FUJITSU_LAPTOP
>  	tristate "Fujitsu Laptop Extras"
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index c32b34a72467..85329fd26afd 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -22,6 +22,7 @@ obj-$(CONFIG_DELL_WMI_AIO)	+= dell-wmi-aio.o
>  obj-$(CONFIG_DELL_WMI_LED)	+= dell-wmi-led.o
>  obj-$(CONFIG_DELL_SMO8800)	+= dell-smo8800.o
>  obj-$(CONFIG_DELL_RBTN)		+= dell-rbtn.o
> +obj-$(CONFIG_DELL_UART_BACKLIGHT) += dell-uart-backlight.o
>  obj-$(CONFIG_ACER_WMI)		+= acer-wmi.o
>  obj-$(CONFIG_ACERHDF)		+= acerhdf.o
>  obj-$(CONFIG_HP_ACCEL)		+= hp_accel.o
> diff --git a/drivers/platform/x86/dell-uart-backlight.c b/drivers/platform/x86/dell-uart-backlight.c
> new file mode 100644
> index 000000000000..7508ceca34a5
> --- /dev/null
> +++ b/drivers/platform/x86/dell-uart-backlight.c
> @@ -0,0 +1,463 @@
> +/*
> + *  Dell AIO Serial Backlight Driver
> + *
> + *  Copyright (C) 2017 AceLan Kao <acelan.kao at canonical.com>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; either version 2 of the License, or
> + *  (at your option) any later version.
> + *
> + *  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.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/acpi.h>
> +#include <linux/serial_8250.h>
> +#include <linux/delay.h>
> +#include <linux/backlight.h>
> +#include <acpi/video.h>
> +
> +#include "dell-uart-backlight.h"
> +
> +struct dell_uart_backlight {
> +	struct device *dev;
> +	struct backlight_device *dell_uart_bd;
> +	struct mutex brightness_mutex;
> +	int line;
> +	int bl_power;
> +};
> +struct uart_8250_port *serial8250_get_port(int line);
> +struct tty_struct *tty;
> +struct file *ftty;
> +
> +unsigned int (*io_serial_in)(struct uart_port *p, int offset);
> +int (*uart_write)(struct tty_struct *tty, const unsigned char *buf, int count);
> +int (*uart_chars_in_buffer)(struct tty_struct *tty);
> +
> +static const struct dell_uart_bl_cmd uart_cmd[] = {
> +	/*
> +	 * Get Firmware Version: Tool uses this command to get firmware version.
> +	 * Command: 0x6A 0x06 0x8F (Length:3 Type: 0x0A, Cmd:6 Checksum:0x8F)
> +	 * Return data: 0x0D 0x06 Data checksum (Length:13,Cmd:0x06,
> +	 * 	        Data :F/W version(APRILIA=APR27-VXXX,PHINE=PHI23-VXXX),
> +	 * 	        checksum:SUM(Length and Cmd and Data)xor 0xFF .
> +	 */
> +	[DELL_UART_GET_FIRMWARE_VER] = {
> +		.cmd	= {0x6A, 0x06, 0x8F},
> +		.tx_len	= 3,
> +	},
> +	/*
> +	 * Get Brightness level: Application uses this command for scaler to get brightness.
> +	 * Command: 0x6A 0x0C 0x89 (Length:3 Type: 0x0A, Cmd:0x0C, Checksum:0x89)
> +	 * Return data: 0x04 0x0C Data checksum
> +	 * (Length:4 Cmd: 0x0C Data: brightness level checksum: SUM(Length and Cmd and Data)xor 0xFF)
> +	 *           brightness level which ranges from 0~100.
> +	 */
> +	[DELL_UART_GET_BRIGHTNESS] = {
> +		.cmd	= {0x6A, 0x0C, 0x89},
> +		.ret	= {0x04, 0x0C, 0x00, 0x00},
> +		.tx_len	= 3,
> +		.rx_len	= 4,
> +	},
> +	/* Set Brightness level: Application uses this command for scaler to set brightness.
> +	 * Command: 0x8A 0x0B Byte2 Checksum (Length:4 Type: 0x0A, Cmd:0x0B)
> +	 * 	    where Byte2 is the brightness level which ranges from 0~100.
> +	 * Return data: 0x03 0x0B 0xF1(Length:3,Cmd:B,checksum:0xF1)
> +	 * Scaler must send the 3bytes ack within 1 second when success, other value if error
> +	 */
> +	[DELL_UART_SET_BRIGHTNESS] = {
> +		.cmd	= {0x8A, 0x0B, 0x0, 0x0},
> +		.ret	= {0x03, 0x0B, 0xF1},
> +		.tx_len	= 4,
> +		.rx_len	= 3,
> +	},
> +	/*
> +	 * Screen ON/OFF Control: Application uses this command to control screen ON or OFF.
> +	 * Command: 0x8A 0x0E Byte2 Checksum (Length:4 Type: 0x0A, Cmd:0x0E) where
> +	 * 	    Byte2=0 to turn OFF the screen.
> +	 * 	    Byte2=1 to turn ON the screen
> +	 * 	    Other value of Byte2 is reserved and invalid.
> +	 * Return data: 0x03 0x0E 0xEE(Length:3,Cmd:E,checksum:0xEE)
> +	 */
> +	[DELL_UART_SET_BACKLIGHT_POWER] = {
> +		.cmd	= {0x8A, 0x0E, 0x00, 0x0},
> +		.ret	= {0x03, 0x0E, 0xEE},
> +		.tx_len	= 4,
> +		.rx_len	= 3,
> +	},
> +};
> +
> +static int dell_uart_write(struct uart_8250_port *up, __u8 *buf, int len)
> +{
> +	int actual = 0;
> +	struct uart_port *port = &up->port;
> +
> +	tty_port_tty_wakeup(&port->state->port);
> +	tty = tty_port_tty_get(&port->state->port);
> +	actual = uart_write(tty, buf, len);
> +	while (uart_chars_in_buffer(tty)) {
> +		udelay(10);
> +	}
> +
> +	return actual;
> +}
> +
> +static int dell_uart_read(struct uart_8250_port *up, __u8 *buf, int len)
> +{
> +	int i, retry;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&up->port.lock, flags);
> +	for (i = 0; i < len; i++) {
> +		retry = 10;
> +		while (!(io_serial_in(&up->port, UART_LSR) & UART_LSR_DR)) {
> +			if (--retry == 0)
> +				break;
> +			mdelay(20);
> +		}
> +
> +		if (retry == 0)
> +			break;
> +		buf[i] = io_serial_in(&up->port, UART_RX);
> +	}
> +	spin_unlock_irqrestore(&up->port.lock, flags);
> +
> +	return i;
> +}
> +
> +static void dell_uart_dump_cmd(const char *func, const char *prefix,
> +			       const char *cmd, int len)
> +{
> +	char buf[80];
> +
> +	snprintf(buf, 80, "dell_uart_backlight:%s:%s", func, prefix);
> +	if (len != 0)
> +		print_hex_dump_debug(buf, DUMP_PREFIX_NONE,
> +					16, 1, cmd, len, false);
> +	else
> +		pr_debug("dell_uart_backlight:%s:%sNULL\n", func, prefix);
> +
> +}
> +
> +/*
> + * checksum: SUM(Length and Cmd and Data)xor 0xFF)
> + */
> +static unsigned char dell_uart_checksum(unsigned char *buf, int len)
> +{
> +	unsigned char val = 0;
> +
> +	while (len-- > 0)
> +		val += buf[len];
> +
> +	return val ^ 0xff;
> +}
> +
> +/*
> + * There is no command to get backlight power status,
> + * so we set the backlight power to "on" while initializing,
> + * and then track and report its status by bl_power variable
> + */
> +static inline int dell_uart_get_bl_power(struct dell_uart_backlight *dell_pdata)
> +{
> +	return dell_pdata->bl_power;
> +}
> +
> +static int dell_uart_set_bl_power(struct backlight_device *bd, int power)
> +{
> +	struct dell_uart_bl_cmd *bl_cmd =
> +		&uart_cmd[DELL_UART_SET_BACKLIGHT_POWER];
> +	struct dell_uart_backlight *dell_pdata = bl_get_data(bd);
> +	struct uart_8250_port *uart = serial8250_get_port(dell_pdata->line);
> +	int rx_len;
> +
> +	if (power != FB_BLANK_POWERDOWN)
> +		power = FB_BLANK_UNBLANK;
> +
> +	bl_cmd->cmd[2] = power ? 0 : 1;
> +	bl_cmd->cmd[3] = dell_uart_checksum(bl_cmd->cmd, bl_cmd->tx_len - 1);
> +
> +	dell_uart_dump_cmd(__func__, "tx: ", bl_cmd->cmd, bl_cmd->tx_len);
> +
> +	if (mutex_lock_killable(&dell_pdata->brightness_mutex) < 0) {
> +		pr_debug("Failed to get mutex_lock");
> +		return 0;
> +	}
> +
> +	dell_uart_write(uart, bl_cmd->cmd, bl_cmd->tx_len);
> +	rx_len = dell_uart_read(uart, bl_cmd->ret, bl_cmd->rx_len);
> +
> +	mutex_unlock(&dell_pdata->brightness_mutex);
> +
> +	dell_uart_dump_cmd(__func__, "rx: ", bl_cmd->ret, rx_len);
> +
> +	bd->props.power = power;
> +	dell_pdata->bl_power = power;
> +
> +	return 0;
> +}
> +
> +static int dell_uart_get_brightness(struct backlight_device *bd)
> +{
> +	struct dell_uart_bl_cmd *bl_cmd = &uart_cmd[DELL_UART_GET_BRIGHTNESS];
> +	struct dell_uart_backlight *dell_pdata = bl_get_data(bd);
> +	struct uart_8250_port *uart = serial8250_get_port(dell_pdata->line);
> +	int rx_len, brightness = 0;
> +
> +	dell_uart_dump_cmd(__func__, "tx: ", bl_cmd->cmd, bl_cmd->tx_len);
> +
> +	if (mutex_lock_killable(&dell_pdata->brightness_mutex) < 0) {
> +		pr_debug("Failed to get mutex_lock");
> +		return 0;
> +	}
> +
> +	dell_uart_write(uart, bl_cmd->cmd, bl_cmd->tx_len);
> +	rx_len = dell_uart_read(uart, bl_cmd->ret, bl_cmd->rx_len);
> +
> +	mutex_unlock(&dell_pdata->brightness_mutex);
> +
> +	dell_uart_dump_cmd(__func__, "rx: ", bl_cmd->ret, rx_len);
> +
> +	brightness = (unsigned int)bl_cmd->ret[2];
> +
> +	return brightness;
> +}
> +
> +static int dell_uart_update_status(struct backlight_device *bd)
> +{
> +	struct dell_uart_bl_cmd *bl_cmd = &uart_cmd[DELL_UART_SET_BRIGHTNESS];
> +	struct dell_uart_backlight *dell_pdata = bl_get_data(bd);
> +	struct uart_8250_port *uart = serial8250_get_port(dell_pdata->line);
> +	int rx_len;
> +
> +	bl_cmd->cmd[2] = bd->props.brightness;
> +	bl_cmd->cmd[3] = dell_uart_checksum(bl_cmd->cmd, bl_cmd->tx_len - 1);
> +
> +	dell_uart_dump_cmd(__func__, "tx: ", bl_cmd->cmd, bl_cmd->tx_len);
> +
> +	if (mutex_lock_killable(&dell_pdata->brightness_mutex) < 0) {
> +		pr_debug("Failed to get mutex_lock");
> +		return 0;
> +	}
> +
> +	dell_uart_write(uart, bl_cmd->cmd, bl_cmd->tx_len);
> +	rx_len = dell_uart_read(uart, bl_cmd->ret, bl_cmd->rx_len);
> +
> +	mutex_unlock(&dell_pdata->brightness_mutex);
> +
> +	dell_uart_dump_cmd(__func__, "rx: ", bl_cmd->ret, rx_len);
> +
> +	if (bd->props.power != dell_uart_get_bl_power(dell_pdata))
> +		dell_uart_set_bl_power(bd, bd->props.power);
> +
> +	return 0;
> +}
> +
> +static int dell_uart_get_scalar_status(struct dell_uart_backlight *dell_pdata)
> +{
> +	struct dell_uart_bl_cmd *bl_cmd = &uart_cmd[DELL_UART_GET_SCALAR];

/tmp/kernel-smb-1b8364d-vWHU/build/drivers/platform/x86/dell-uart-backlight.c:
In function 'dell_uart_get_scalar_status':
/tmp/kernel-smb-1b8364d-vWHU/build/drivers/platform/x86/dell-uart-backlight.c:263:46:
error: 'DELL_UART_GET_SCALAR' undeclared (first use in this function); did you
mean 'DELL_UART_GET_BRIGHTNESS'?
  struct dell_uart_bl_cmd *bl_cmd = &uart_cmd[DELL_UART_GET_SCALAR];
                                              ^~~~~~~~~~~~~~~~~~~~
                                              DELL_UART_GET_BRIGHTNESS
/tmp/kernel-smb-1b8364d-vWHU/build/drivers/platform/x86/dell-uart-backlight.c:263:46:
note: each undeclared identifier is reported only once for each function it
appears in
/tmp/kernel-smb-1b8364d-vWHU/build/drivers/platform/x86/dell-uart-backlight.c:
In function 'dell_uart_show_firmware_ver':
/tmp/kernel-smb-1b8364d-vWHU/build/drivers/platform/x86/dell-uart-backlight.c:289:36:
warning: initialization discards 'const' qualifier from pointer target type
[-Wdiscarded-qualifiers]
  struct dell_uart_bl_cmd *bl_cmd = &uart_cmd[DELL_UART_GET_FIRMWARE_VER];
                                    ^
  CC [M]  net/sched/act_nat.o
/tmp/kernel-smb-1b8364d-vWHU/build/drivers/platform/x86/dell-uart-backlight.c:
In function 'dell_uart_bl_add':
  CC [M]  drivers/media/v4l2-core/tuner-core.o
/tmp/kernel-smb-1b8364d-vWHU/build/drivers/platform/x86/dell-uart-backlight.c:367:48:
warning: logical not is only applied to the left hand side of comparison
[-Wlogical-not-parentheses]
   if (!dell_uart_show_firmware_ver(dell_pdata) <= 0) {
                                                ^~
/tmp/kernel-smb-1b8364d-vWHU/build/drivers/platform/x86/dell-uart-backlight.c:367:7:
note: add parentheses around left hand side expression to silence this warning
   if (!dell_uart_show_firmware_ver(dell_pdata) <= 0) {
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       (                                       )
  CC [M]  drivers/media/v4l2-core/v4l2-mem2mem.o
> +	struct uart_8250_port *uart = serial8250_get_port(dell_pdata->line);
> +	int rx_len, status = 1; /* assume the scalar IC controls backlight if the command failed */
> +
> +	dell_uart_dump_cmd(__func__, "tx: ", bl_cmd->cmd, bl_cmd->tx_len);
> +
> +	if (mutex_lock_killable(&dell_pdata->brightness_mutex) < 0) {
> +		pr_debug("Failed to get mutex_lock");
> +		return 0;
> +	}
> +
> +	dell_uart_write(uart, bl_cmd->cmd, bl_cmd->tx_len);
> +	rx_len = dell_uart_read(uart, bl_cmd->ret, bl_cmd->rx_len);
> +
> +	mutex_unlock(&dell_pdata->brightness_mutex);
> +
> +	dell_uart_dump_cmd(__func__, "rx: ", bl_cmd->ret, rx_len);
> +
> +	if (rx_len == 4)
> +		status = (unsigned int)bl_cmd->ret[2];
> +
> +	return status;
> +}
> +
> +static int dell_uart_show_firmware_ver(struct dell_uart_backlight *dell_pdata)
> +{
> +	struct dell_uart_bl_cmd *bl_cmd = &uart_cmd[DELL_UART_GET_FIRMWARE_VER];
> +	struct uart_8250_port *uart = serial8250_get_port(dell_pdata->line);
> +	int rx_len = 0, retry = 10;
> +
> +	dell_uart_dump_cmd(__func__, "tx: ", bl_cmd->cmd, bl_cmd->tx_len);
> +
> +	if (mutex_lock_killable(&dell_pdata->brightness_mutex) < 0) {
> +		pr_debug("Failed to get mutex_lock");
> +		return -1;
> +	}
> +
> +	dell_uart_write(uart, bl_cmd->cmd, bl_cmd->tx_len);
> +	while (retry-- > 0) {
> +		/* first byte is data length */
> +		dell_uart_read(uart, bl_cmd->ret, 1);
> +		rx_len = (int)bl_cmd->ret[0];
> +		if (bl_cmd->ret[0] > 80 || bl_cmd->ret[0] <= 0) {
> +			pr_debug("Failed to get firmware version\n");
> +			if (retry == 0) {
> +				mutex_unlock(&dell_pdata->brightness_mutex);
> +				return -1;
> +			}
> +			msleep(100);
> +			continue;
> +		}
> +
> +		dell_uart_read(uart, bl_cmd->ret+1, rx_len-1);
> +		break;
> +	}
> +	mutex_unlock(&dell_pdata->brightness_mutex);
> +
> +	dell_uart_dump_cmd(__func__, "rx: ", bl_cmd->ret, rx_len);
> +
> +	pr_debug("Firmare str(%d)= %s\n", (int)bl_cmd->ret[0], bl_cmd->ret+2);
> +	return rx_len;
> +}
> +
> +static const struct backlight_ops dell_uart_backlight_ops = {
> +	.get_brightness = dell_uart_get_brightness,
> +	.update_status = dell_uart_update_status,
> +};
> +
> +static int dell_uart_startup(struct dell_uart_backlight *dell_pdata)
> +{
> +	struct uart_8250_port *uartp;
> +	struct uart_port *port;
> +
> +	dell_pdata->line = 0;
> +	uartp = serial8250_get_port(dell_pdata->line);
> +	port = &uartp->port;
> +	tty = port->state->port.tty;
> +	io_serial_in = port->serial_in;
> +	uart_write = tty->driver->ops->write;
> +	uart_chars_in_buffer = tty->driver->ops->chars_in_buffer;
> +
> +	return 0;
> +}
> +
> +static int dell_uart_bl_add(struct acpi_device *dev)
> +{
> +	struct dell_uart_backlight *dell_pdata;
> +	struct backlight_properties props;
> +	struct backlight_device *dell_uart_bd;
> +
> +	dell_pdata = kzalloc(sizeof(struct dell_uart_backlight), GFP_KERNEL);
> +	if (!dell_pdata) {
> +		pr_debug("Failed to allocate memory for dell_uart_backlight\n");
> +		return -1;
> +	}
> +	dell_pdata->dev = &dev->dev;
> +	dell_uart_startup(dell_pdata);
> +	dev->driver_data = dell_pdata;
> +
> +	mutex_init(&dell_pdata->brightness_mutex);
> +
> +	if (!dell_uart_get_scalar_status(dell_pdata)) {
> +		udelay(50);
> +		/* try another command to make sure there is no scalar IC */
> +		if (!dell_uart_show_firmware_ver(dell_pdata) <= 0) {
> +			pr_debug("Scalar doesn't in charge of brightness adjustment.\n");
> +			kzfree(dell_pdata);
> +			return -1;
> +		}
> +	}
> +
> +	memset(&props, 0, sizeof(struct backlight_properties));
> +	props.type = BACKLIGHT_PLATFORM;
> +	props.max_brightness = 100;
> +
> +	dell_uart_bd = backlight_device_register("dell_uart_backlight",
> +						 &dev->dev,
> +						 dell_pdata,
> +						 &dell_uart_backlight_ops,
> +						 &props);
> +	if (IS_ERR(dell_uart_bd)) {
> +		kzfree(dell_pdata);
> +		pr_debug("Backlight registration failed\n");
> +		return -1;
> +	}
> +
> +	dell_pdata->dell_uart_bd = dell_uart_bd;
> +
> +	dell_uart_set_bl_power(dell_uart_bd, FB_BLANK_UNBLANK);
> +	dell_uart_bd->props.brightness = 100;
> +	backlight_update_status(dell_uart_bd);
> +
> +	/* unregister acpi backlight interface */
> +	acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
> +
> +	return 0;
> +}
> +
> +static int dell_uart_bl_remove(struct acpi_device *dev)
> +{
> +	struct dell_uart_backlight *dell_pdata = dev->driver_data;
> +
> +	backlight_device_unregister(dell_pdata->dell_uart_bd);
> +	kzfree(dell_pdata);
> +
> +	return 0;
> +}
> +
> +static int dell_uart_bl_suspend(struct device *dev)
> +{
> +	filp_close(ftty, NULL);
> +	return 0;
> +}
> +
> +static int dell_uart_bl_resume(struct device *dev)
> +{
> +	ftty = filp_open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY, 0);
> +	return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(dell_uart_bl_pm, dell_uart_bl_suspend, dell_uart_bl_resume);
> +
> +static const struct acpi_device_id dell_uart_bl_ids[] = {
> +	{"DELL0501", 0},
> +	{"", 0},
> +};
> +
> +static struct acpi_driver dell_uart_backlight_driver = {
> +	.name = "Dell AIO serial backlight",
> +	.ids = dell_uart_bl_ids,
> +	.ops = {
> +		.add = dell_uart_bl_add,
> +		.remove = dell_uart_bl_remove,
> +	},
> +	.drv.pm = &dell_uart_bl_pm,
> +};
> +
> +static int __init dell_uart_bl_init(void)
> +{
> +	ftty = filp_open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY, 0);
> +	if (IS_ERR(ftty)) {
> +		pr_debug("cannot open /dev/ttyS0\n");
> +		return -EINVAL;
> +	}
> +
> +	return acpi_bus_register_driver(&dell_uart_backlight_driver);
> +}
> +
> +static void __exit dell_uart_bl_exit(void)
> +{
> +	filp_close(ftty, NULL);
> +
> +	acpi_bus_unregister_driver(&dell_uart_backlight_driver);
> +}
> +
> +module_init(dell_uart_bl_init);
> +module_exit(dell_uart_bl_exit);
> +MODULE_DEVICE_TABLE(acpi, dell_uart_bl_ids);
> +MODULE_DESCRIPTION("Dell AIO Serial Backlight module");
> +MODULE_AUTHOR("AceLan Kao <acelan.kao at canonical.com>");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/platform/x86/dell-uart-backlight.h b/drivers/platform/x86/dell-uart-backlight.h
> new file mode 100644
> index 000000000000..4e32b5df76dc
> --- /dev/null
> +++ b/drivers/platform/x86/dell-uart-backlight.h
> @@ -0,0 +1,35 @@
> +/*
> + *  Dell AIO Serial Backlight Driver
> + *
> + *  Copyright (C) 2017 AceLan Kao <acelan.kao at canonical.com>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; either version 2 of the License, or
> + *  (at your option) any later version.
> + *
> + *  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.
> + *
> + */
> +
> +#ifndef _DELL_UART_BACKLIGHT_H_
> +#define _DELL_UART_BACKLIGHT_H_
> +
> +enum {
> +	DELL_UART_GET_FIRMWARE_VER,
> +	DELL_UART_GET_BRIGHTNESS,
> +	DELL_UART_SET_BRIGHTNESS,
> +	DELL_UART_SET_BACKLIGHT_POWER,
> +};
> +
> +struct dell_uart_bl_cmd {
> +	unsigned char	cmd[10];
> +	unsigned char	ret[80];
> +	unsigned short	tx_len;
> +	unsigned short	rx_len;
> +};
> +
> +#endif /* _DELL_UART_BACKLIGHT_H_ */
> 


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