drivers/video/backlight/pandora_bl.c

Source file repositories/reference/linux-study-clean/drivers/video/backlight/pandora_bl.c

File Facts

System
Linux kernel
Corpus path
drivers/video/backlight/pandora_bl.c
Extension
.c
Size
4202 bytes
Lines
160
Domain
Driver Families
Bucket
drivers/video
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct pandora_private {
	unsigned old_state;
#define PANDORABL_WAS_OFF 1
};

static int pandora_backlight_update_status(struct backlight_device *bl)
{
	int brightness = bl->props.brightness;
	struct pandora_private *priv = bl_get_data(bl);
	u8 r;

	if (bl->props.power != BACKLIGHT_POWER_ON)
		brightness = 0;
	if (bl->props.state & BL_CORE_FBBLANK)
		brightness = 0;
	if (bl->props.state & BL_CORE_SUSPENDED)
		brightness = 0;

	if ((unsigned int)brightness > MAX_USER_VALUE)
		brightness = MAX_USER_VALUE;

	if (brightness == 0) {
		if (priv->old_state == PANDORABL_WAS_OFF)
			goto done;

		/* first disable PWM0 output, then clock */
		twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
		r &= ~PWM0_ENABLE;
		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
		r &= ~PWM0_CLK_ENABLE;
		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);

		goto done;
	}

	if (priv->old_state == PANDORABL_WAS_OFF) {
		/*
		 * set PWM duty cycle to max. TPS61161 seems to use this
		 * to calibrate it's PWM sensitivity when it starts.
		 */
		twl_i2c_write_u8(TWL_MODULE_PWM, MAX_VALUE, TWL_PWM0_OFF);

		/* first enable clock, then PWM0 out */
		twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
		r &= ~PWM0_ENABLE;
		r |= PWM0_CLK_ENABLE;
		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
		r |= PWM0_ENABLE;
		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);

		/*
		 * TI made it very easy to enable digital control, so easy that
		 * it often triggers unintentionally and disabes PWM control,
		 * so wait until 1 wire mode detection window ends.
		 */
		usleep_range(2000, 10000);
	}

	twl_i2c_write_u8(TWL_MODULE_PWM, MIN_VALUE + brightness, TWL_PWM0_OFF);

done:
	if (brightness != 0)
		priv->old_state = 0;
	else
		priv->old_state = PANDORABL_WAS_OFF;

	return 0;
}

static const struct backlight_ops pandora_backlight_ops = {
	.options	= BL_CORE_SUSPENDRESUME,
	.update_status	= pandora_backlight_update_status,
};

static int pandora_backlight_probe(struct platform_device *pdev)
{
	struct backlight_properties props;
	struct backlight_device *bl;
	struct pandora_private *priv;
	u8 r;

	priv = devm_kmalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	memset(&props, 0, sizeof(props));
	props.max_brightness = MAX_USER_VALUE;
	props.type = BACKLIGHT_RAW;
	bl = devm_backlight_device_register(&pdev->dev, pdev->name, &pdev->dev,
					priv, &pandora_backlight_ops, &props);

Annotation

Implementation Notes