Cc'ing Daniel Thompson, the new Maintainer. On Sat, 21 Jan 2017, Miłosz Rachwał wrote:
> 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 <[email protected]> > --- > 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 <[email protected]> > + * > + * 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 <[email protected]>"); > +MODULE_DESCRIPTION("VESA DDC/CI MCCS brightness driver"); > +MODULE_LICENSE("GPL"); -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
