Re: [PATCH] platform/x86: dell-uart-backlight: new backlight driver for DELL AIO

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On 26/10/17 16:54, Mario.Limonciello@xxxxxxxx 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@xxxxxxxxxxxxx>");
+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@xxxxxxxxxxxxx>
+ *
+ *  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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