Messages in this thread Patch in this message | | | From | Miłosz Rachwał <> | Subject | [PATCH] backlight: add DDC/CI brightness driver | Date | Sat, 21 Jan 2017 19:31:51 +0100 |
| |
This patch contains driver for exposing VESA DDC/CI MCCS brightness settings via kernel backlight API. This allows to control monitor brightness using standard software which uses /sys/class/backlight/ interface, same as for laptop backlight drivers. Because some monitors don't correctly implement DDC/CI standard module parameter allows to override maximum brightness value reported by monitor. This module doesn't support autodetection, so driver must be manually instantiated on monitor I²C bus under 0x37 address.
Signed-off-by: Miłosz Rachwał <me@milek7.pl> --- drivers/video/backlight/Kconfig | 7 ++ drivers/video/backlight/Makefile | 1 + drivers/video/backlight/ddcci_bl.c | 128 +++++++++++++++++++++++++++++++++++++ 3 files changed, 136 insertions(+) create mode 100644 drivers/video/backlight/ddcci_bl.c
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig index 5ffa4b4e..cce62832 100644 --- a/drivers/video/backlight/Kconfig +++ b/drivers/video/backlight/Kconfig @@ -460,6 +460,13 @@ config BACKLIGHT_BD6107 help If you have a Rohm BD6107 say Y to enable the backlight driver. +config BACKLIGHT_DDCCI + tristate "VESA DDC/CI MCCS brightness driver" + depends on BACKLIGHT_CLASS_DEVICE && I2C + default m + help + This supports brightness control via VESA DDC/CI MCCS. + endif # BACKLIGHT_CLASS_DEVICE endif # BACKLIGHT_LCD_SUPPORT diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile index 16ec534c..2e5352aa 100644 --- a/drivers/video/backlight/Makefile +++ b/drivers/video/backlight/Makefile @@ -30,6 +30,7 @@ obj-$(CONFIG_BACKLIGHT_CARILLO_RANCH) += cr_bllcd.o obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE) += backlight.o obj-$(CONFIG_BACKLIGHT_DA903X) += da903x_bl.o obj-$(CONFIG_BACKLIGHT_DA9052) += da9052_bl.o +obj-$(CONFIG_BACKLIGHT_DDCCI) += ddcci_bl.o obj-$(CONFIG_BACKLIGHT_EP93XX) += ep93xx_bl.o obj-$(CONFIG_BACKLIGHT_GENERIC) += generic_bl.o obj-$(CONFIG_BACKLIGHT_GPIO) += gpio_backlight.o diff --git a/drivers/video/backlight/ddcci_bl.c b/drivers/video/backlight/ddcci_bl.c new file mode 100644 index 00000000..c314cbc8 --- /dev/null +++ b/drivers/video/backlight/ddcci_bl.c @@ -0,0 +1,128 @@ +/* + * VESA DDC/CI MCCS brightness driver + * + * Copyright (C) 2017 Miłosz Rachwał <me@milek7.pl> + * + * 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. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/i2c.h> +#include <linux/backlight.h> +#include <linux/delay.h> + +static int maxbr; +module_param(maxbr, int, 0644); +MODULE_PARM_DESC(maxbr, "Override maximum brightness value specified by monitor"); + +static int ddcci_update_status(struct backlight_device *bl) +{ + struct i2c_client *client = bl_get_data(bl); + + char buf[] = { 0x51, 0x84, 0x03, 0x10, 0x00, 0x00, 0x00 }; + buf[4] = bl->props.brightness >> 8; + buf[5] = bl->props.brightness; + buf[6] = (client->addr << 1) ^ 0xC6 ^ buf[4] ^ buf[5]; + + i2c_master_send(client, buf, 7); + msleep(50); + + return 0; +} + +static int ddcci_read(struct i2c_client *client, struct backlight_properties *props, int init) +{ + int i; + char xor; + + char buf[11] = { 0x51, 0x82, 0x01, 0x10, 0x00 }; + buf[4] = (client->addr << 1) ^ 0xC2; + + i2c_master_send(client, buf, 5); + msleep(40); + i2c_master_recv(client, buf, 11); + + if (buf[3] != 0) + goto fail; + + xor = 0x50; + for (i = 0; i < 11; i++) + xor ^= buf[i]; + + if (xor) + goto fail; + + if (init) { + if (maxbr) + props->max_brightness = maxbr; + else + props->max_brightness = (buf[6] << 8) | buf[7]; + } + props->brightness = (buf[8] << 8) | buf[9]; + + return 0; + +fail: + dev_err(&client->dev, "failed to read brightness"); + return -1; +} + +static int ddcci_get_brightness(struct backlight_device *bl) +{ + struct i2c_client *client = bl_get_data(bl); + + ddcci_read(client, &bl->props, 0); + return bl->props.brightness; +} + +static const struct backlight_ops ddcci_ops = { + .update_status = ddcci_update_status, + .get_brightness = ddcci_get_brightness +}; + +static int ddcci_probe(struct i2c_client *client, const struct i2c_device_id *id) +{ + struct backlight_properties props; + int retry; + char name[20]; + + memset(&props, 0, sizeof(struct backlight_properties)); + props.type = BACKLIGHT_FIRMWARE; + snprintf(name, 20, "ddcci_%s", dev_name(&client->dev)); + + for (retry = 0; retry < 3; retry++) { + if (ddcci_read(client, &props, 1) >= 0) { + devm_backlight_device_register(&client->dev, name, &client->dev, client, &ddcci_ops, &props); + return 0; + } + } + + return -1; +} + +static int ddcci_remove(struct i2c_client *client) +{ + return 0; +} + +static struct i2c_device_id ddcci_idtable[] = { + { "ddcci_bl", 0 }, + {} +}; +MODULE_DEVICE_TABLE(i2c, ddcci_idtable); + +static struct i2c_driver ddcci_driver = { + .driver = { .name = "ddcci_bl" }, + .id_table = ddcci_idtable, + .probe = ddcci_probe, + .remove = ddcci_remove +}; +module_i2c_driver(ddcci_driver); + +MODULE_AUTHOR("Miłosz Rachwał <me@milek7.pl>"); +MODULE_DESCRIPTION("VESA DDC/CI MCCS brightness driver"); +MODULE_LICENSE("GPL"); -- 2.11.0
| |