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    SubjectRe: [PATCH] platform/x86: dell-uart-backlight: new backlight driver for DELL AIO
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    On 26/10/17 16:54, Mario.Limonciello@dell.com wrote:
    >> +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);
    >> + dell_pdata->dev = &dev->dev;
    >> + dell_uart_startup(dell_pdata);
    >> + dev->driver_data = dell_pdata;
    >> +
    >> + mutex_init(&dell_pdata->brightness_mutex);
    >> +
    >> + memset(&props, 0, sizeof(struct backlight_properties));
    >> + props.type = BACKLIGHT_PLATFORM;
    >> + props.max_brightness = 100;
    >
    > Is the memset of zero actually necessary? Of the items in
    > backlight_properties:
    > * you set brightness a few lines later
    > (after it's been memcpy'ed in the backlight device)
    > * You set max brightness explicitly
    > * You set power a few lines below
    >
    > So the only attribute missing is fb_blank. That's marked "to be removed".

    fb_blank may be scheduled for removal but it is still honored by the
    backlight core so it should definitely not be left undefined.

    I reviewed this recently and concluded that all drivers default it to
    unblanked (mostly by a memset like the one above). Without this then I
    think there is a risk that some code paths through DRM drivers won't
    turn the backlight on.


    Daniel.


    >> +
    >> + dell_uart_bd = backlight_device_register("dell_uart_backlight",
    >> + &dev->dev,
    >> + dell_pdata,
    >> + &dell_uart_backlight_ops,
    >> + &props);
    >> + dell_pdata->dell_uart_bd = dell_uart_bd;
    >> +
    >> + dell_uart_show_firmware_ver(dell_pdata);
    >> + 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);
    >
    > Since you change this when the driver is loaded, you should cache the old
    > value and restore it when the driver is unloaded too.
    >
    >> +
    >> + 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);
    >> +
    >> + 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);
    >
    > I guess this is to prevent other userspace apps from accessing the port
    > simultaneously right? I think you'll need to check if the open failed
    > IS_ERR(ftty)
    > or similar to make sure that this driver would fail to load if the file
    > didn't exist or was opened by userspace with an exclusive lock or something.
    >
    >> +
    >> + 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@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 0000000..b8bca12
    >> --- /dev/null
    >> +++ b/drivers/platform/x86/dell-uart-backlight.h
    >> @@ -0,0 +1,88 @@
    >> +/*
    >> + * Dell AIO Serial Backlight Driver
    >> + *
    >> + * Copyright (C) 2017 AceLan Kao <acelan.kao@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;
    >> +};
    >> +
    >> +static 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,
    >> + },
    >> +};
    >> +
    >> +#endif /* _DELL_UART_BACKLIGHT_H_ */
    >> --
    >> 2.7.4
    >

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