Commit 6202b5de authored by Hans de Goede's avatar Hans de Goede Committed by Lee Jones
Browse files

backlight: lp855x: Add support ACPI enumeration 



The Xiaomi Mi Pad 2 tablet uses an ACPI enumerated LP8556 backlight
controller for its LCD-panel, with a Xiaomi specific ACPI HID of
"XMCC0001", add support for this.

Note the new "if (id)" check also fixes a NULL pointer deref when a user
tries to manually bind the driver from sysfs.

When CONFIG_ACPI is disabled acpi_match_device() will always return NULL,
so the lp855x_parse_acpi() call will get optimized away.

Reviewed-by: default avatarDaniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211102225504.18920-3-hdegoede@redhat.com
parent 92add941

drivers/video/backlight/lp855x_bl.c

+61 −12
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
 *			Copyright (C) 2011 Texas Instruments

 */



#include <linux/acpi.h>

#include <linux/module.h>

#include <linux/slab.h>

#include <linux/i2c.h>
@@ -330,7 +331,7 @@ static int lp855x_parse_dt(struct lp855x *lp) 
{

	struct device *dev = lp->dev;

	struct device_node *node = dev->of_node;

	struct lp855x_platform_data *pdata;

	struct lp855x_platform_data *pdata = lp->pdata;

	int rom_length;



	if (!node) {
@@ -338,10 +339,6 @@ static int lp855x_parse_dt(struct lp855x *lp) 
		return -EINVAL;

	}



	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);

	if (!pdata)

		return -ENOMEM;



	of_property_read_string(node, "bl-name", &pdata->name);

	of_property_read_u8(node, "dev-ctrl", &pdata->device_control);

	of_property_read_u8(node, "init-brt", &pdata->initial_brightness);
@@ -368,8 +365,6 @@ static int lp855x_parse_dt(struct lp855x *lp) 
		pdata->rom_data = &rom[0];

	}



	lp->pdata = pdata;



	return 0;

}

#else
@@ -379,8 +374,32 @@ static int lp855x_parse_dt(struct lp855x *lp) 
}

#endif



static int lp855x_parse_acpi(struct lp855x *lp)

{

	int ret;



	/*

	 * On ACPI the device has already been initialized by the firmware

	 * and is in register mode, so we can read back the settings from

	 * the registers.

	 */

	ret = i2c_smbus_read_byte_data(lp->client, lp->cfg->reg_brightness);

	if (ret < 0)

		return ret;



	lp->pdata->initial_brightness = ret;



	ret = i2c_smbus_read_byte_data(lp->client, lp->cfg->reg_devicectrl);

	if (ret < 0)

		return ret;



	lp->pdata->device_control = ret;

	return 0;

}



static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)

{

	const struct acpi_device_id *acpi_id = NULL;

	struct device *dev = &cl->dev;

	struct lp855x *lp;

	int ret;
@@ -394,9 +413,19 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id) 


	lp->client = cl;

	lp->dev = dev;

	lp->pdata = dev_get_platdata(dev);



	if (id) {

		lp->chipname = id->name;

		lp->chip_id = id->driver_data;

	lp->pdata = dev_get_platdata(dev);

	} else {

		acpi_id = acpi_match_device(dev->driver->acpi_match_table, dev);

		if (!acpi_id)

			return -ENODEV;



		lp->chipname = acpi_id->id;

		lp->chip_id = acpi_id->driver_data;

	}



	switch (lp->chip_id) {

	case LP8550:
@@ -415,9 +444,19 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id) 
	}



	if (!lp->pdata) {

		lp->pdata = devm_kzalloc(dev, sizeof(*lp->pdata), GFP_KERNEL);

		if (!lp->pdata)

			return -ENOMEM;



		if (id) {

			ret = lp855x_parse_dt(lp);

			if (ret < 0)

				return ret;

		} else {

			ret = lp855x_parse_acpi(lp);

			if (ret < 0)

				return ret;

		}

	}



	if (lp->pdata->period_ns > 0)
@@ -537,10 +576,20 @@ static const struct i2c_device_id lp855x_ids[] = { 
};

MODULE_DEVICE_TABLE(i2c, lp855x_ids);



#ifdef CONFIG_ACPI

static const struct acpi_device_id lp855x_acpi_match[] = {

	/* Xiaomi specific HID used for the LP8556 on the Mi Pad 2 */

	{ "XMCC0001", LP8556 },

	{ }

};

MODULE_DEVICE_TABLE(acpi, lp855x_acpi_match);

#endif



static struct i2c_driver lp855x_driver = {

	.driver = {

		   .name = "lp855x",

		   .of_match_table = of_match_ptr(lp855x_dt_ids),

		   .acpi_match_table = ACPI_PTR(lp855x_acpi_match),

		   },

	.probe = lp855x_probe,

	.remove = lp855x_remove,