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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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