On Tue, Nov 25, 2025 at 03:29:39PM +0000, Petri Karhula via B4 Relay wrote:
> From: Petri Karhula <[email protected]>
>
> This driver provides backlight brightness control through the Linux
> backlight subsystem. It communicates with the board controller to
> adjust LCD backlight using PWM signals. Communication is done
> through Congatec Board Controller core driver.
>
> Signed-off-by: Petri Karhula <[email protected]>
> ---
> drivers/video/backlight/Kconfig | 11 +++
> drivers/video/backlight/Makefile | 1 +
> drivers/video/backlight/cgbc_bl.c | 177
> ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 189 insertions(+)
> +static int cgbc_bl_probe(struct platform_device *pdev)
> +{
> + struct cgbc_device_data *cgbc = dev_get_drvdata(pdev->dev.parent);
> + struct backlight_properties props = { };
> + u8 cmd_buf[4] = { CGBC_CMD_BLT0_PWM };
> + struct backlight_device *bl_dev;
> + struct cgbc_bl_data *bl_data;
> + u8 reply_buf[3];
> + int ret;
> +
> + bl_data = devm_kzalloc(&pdev->dev, sizeof(*bl_data), GFP_KERNEL);
> + if (!bl_data)
> + return -ENOMEM;
> +
> + bl_data->dev = &pdev->dev;
> + bl_data->cgbc = cgbc;
> +
> + ret = cgbc_command(bl_data->cgbc, cmd_buf, sizeof(cmd_buf), reply_buf,
> + sizeof(reply_buf), NULL);
> + if (ret < 0)
> + return dev_err_probe(&pdev->dev, ret,
> + "Failed to read initial brightness\n");
> +
> + /*
> + * Get only PWM duty factor percentage,
> + * ignore polarity inversion bit (bit 7)
> + */
> + bl_data->current_brightness = FIELD_GET(BLT_PWM_DUTY_MASK,
> reply_buf[0]);
It would good to common this up with cgbc_bl_get_brightness() by
providing a helper that takes struct cgbc_bl_data * and calling it
from both places.
> +
> + props.type = BACKLIGHT_PLATFORM;
> + props.max_brightness = CGBC_BL_MAX_BRIGHTNESS;
> + props.brightness = bl_data->current_brightness;
New drivers should always set props.scale .
> +
> + bl_dev = devm_backlight_device_register(&pdev->dev, "cgbc-backlight",
> + &pdev->dev, bl_data,
> + &cgbc_bl_ops, &props);
> + if (IS_ERR(bl_dev))
> + return dev_err_probe(&pdev->dev, PTR_ERR(bl_dev),
> + "Failed to register backlight device\n");
> +
> + platform_set_drvdata(pdev, bl_data);
> +
> + return 0;
> +}
> +
> +static struct platform_driver cgbc_bl_driver = {
> + .driver = {
> + .name = "cgbc-backlight",
> + },
> + .probe = cgbc_bl_probe,
> +};
Daniel.
