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backlight: lp855x: Add support ACPI enumeration

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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: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211102225504.18920-3-hdegoede@redhat.com
This commit is contained in:
Hans de Goede 2021-11-02 23:55:04 +01:00 committed by Lee Jones
parent 92add941b6
commit 6202b5de73
1 changed files with 61 additions and 12 deletions
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73
drivers/video/backlight/lp855x_bl.c
View File

@ -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;
@ -394,10 +413,20 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
lp->client = cl;
lp->dev = dev;
lp->chipname = id->name;
lp->chip_id = id->driver_data;
lp->pdata = dev_get_platdata(dev);
if (id) {
lp->chipname = id->name;
lp->chip_id = id->driver_data;
} 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:
case LP8551:
@ -415,9 +444,19 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
}
if (!lp->pdata) {
ret = lp855x_parse_dt(lp);
if (ret < 0)
return ret;
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,