[PATCH 1/3] backlight: lp855x: Move device_config setting out of lp855x_configure()

[PATCH 1/3] backlight: lp855x: Move device_config setting out of lp855x_configure()

[Hans de Goede]

Move the setting of the lp->cfg pointer to the chip specific
lp855x_device_config struct from lp855x_configure() to
lp855x_probe(), before calling lp855x_parse_dt().

This is a preperation patch for adding ACPI enumeration support.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/video/backlight/lp855x_bl.c | 32 ++++++++++++++---------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
index e94932c69f54..808ff00b2003 100644
--- a/drivers/video/backlight/lp855x_bl.c
+++ b/drivers/video/backlight/lp855x_bl.c
@@ -170,22 +170,6 @@ static int lp855x_configure(struct lp855x *lp)
 	int i, ret;
 	struct lp855x_platform_data *pd = lp->pdata;
 
-	switch (lp->chip_id) {
-	case LP8550:
-	case LP8551:
-	case LP8552:
-	case LP8553:
-	case LP8556:
-		lp->cfg = &lp855x_dev_cfg;
-		break;
-	case LP8555:
-	case LP8557:
-		lp->cfg = &lp8557_dev_cfg;
-		break;
-	default:
-		return -EINVAL;
-	}
-
 	if (lp->cfg->pre_init_device) {
 		ret = lp->cfg->pre_init_device(lp);
 		if (ret) {
@@ -413,6 +397,22 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
 	lp->chip_id = id->driver_data;
 	lp->pdata = dev_get_platdata(&cl->dev);
 
+	switch (lp->chip_id) {
+	case LP8550:
+	case LP8551:
+	case LP8552:
+	case LP8553:
+	case LP8556:
+		lp->cfg = &lp855x_dev_cfg;
+		break;
+	case LP8555:
+	case LP8557:
+		lp->cfg = &lp8557_dev_cfg;
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	if (!lp->pdata) {
 		ret = lp855x_parse_dt(lp);
 		if (ret < 0)
-- 
2.31.1

[PATCH 2/3] backlight: lp855x: Add dev helper variable to lp855x_probe()

[Hans de Goede]

Add a dev local variable to the lp855x_probe(), to replace "&cl->dev"
and "lp->dev" in various places.

Also switch to dev_err_probe() in one case which takes care of not
printing -EPROBE_DEFER errors for us.

This is mostly a preparation for adding ACPI enumeration support which
will use the new "dev" variable more.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/video/backlight/lp855x_bl.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
index 808ff00b2003..d1d27d5eb0f2 100644
--- a/drivers/video/backlight/lp855x_bl.c
+++ b/drivers/video/backlight/lp855x_bl.c
@@ -381,21 +381,22 @@ static int lp855x_parse_dt(struct lp855x *lp)
 
 static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
 {
+	struct device *dev = &cl->dev;
 	struct lp855x *lp;
 	int ret;
 
 	if (!i2c_check_functionality(cl->adapter, I2C_FUNC_SMBUS_I2C_BLOCK))
 		return -EIO;
 
-	lp = devm_kzalloc(&cl->dev, sizeof(struct lp855x), GFP_KERNEL);
+	lp = devm_kzalloc(dev, sizeof(struct lp855x), GFP_KERNEL);
 	if (!lp)
 		return -ENOMEM;
 
 	lp->client = cl;
-	lp->dev = &cl->dev;
+	lp->dev = dev;
 	lp->chipname = id->name;
 	lp->chip_id = id->driver_data;
-	lp->pdata = dev_get_platdata(&cl->dev);
+	lp->pdata = dev_get_platdata(dev);
 
 	switch (lp->chip_id) {
 	case LP8550:
@@ -424,30 +425,27 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
 	else
 		lp->mode = REGISTER_BASED;
 
-	lp->supply = devm_regulator_get(lp->dev, "power");
+	lp->supply = devm_regulator_get(dev, "power");
 	if (IS_ERR(lp->supply)) {
 		if (PTR_ERR(lp->supply) == -EPROBE_DEFER)
 			return -EPROBE_DEFER;
 		lp->supply = NULL;
 	}
 
-	lp->enable = devm_regulator_get_optional(lp->dev, "enable");
+	lp->enable = devm_regulator_get_optional(dev, "enable");
 	if (IS_ERR(lp->enable)) {
 		ret = PTR_ERR(lp->enable);
 		if (ret == -ENODEV) {
 			lp->enable = NULL;
 		} else {
-			if (ret != -EPROBE_DEFER)
-				dev_err(lp->dev, "error getting enable regulator: %d\n",
-					ret);
-			return ret;
+			return dev_err_probe(dev, ret, "getting enable regulator\n");
 		}
 	}
 
 	if (lp->supply) {
 		ret = regulator_enable(lp->supply);
 		if (ret < 0) {
-			dev_err(&cl->dev, "failed to enable supply: %d\n", ret);
+			dev_err(dev, "failed to enable supply: %d\n", ret);
 			return ret;
 		}
 	}
@@ -455,7 +453,7 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
 	if (lp->enable) {
 		ret = regulator_enable(lp->enable);
 		if (ret < 0) {
-			dev_err(lp->dev, "failed to enable vddio: %d\n", ret);
+			dev_err(dev, "failed to enable vddio: %d\n", ret);
 			goto disable_supply;
 		}
 
@@ -470,20 +468,19 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
 
 	ret = lp855x_configure(lp);
 	if (ret) {
-		dev_err(lp->dev, "device config err: %d", ret);
+		dev_err(dev, "device config err: %d", ret);
 		goto disable_vddio;
 	}
 
 	ret = lp855x_backlight_register(lp);
 	if (ret) {
-		dev_err(lp->dev,
-			"failed to register backlight. err: %d\n", ret);
+		dev_err(dev, "failed to register backlight. err: %d\n", ret);
 		goto disable_vddio;
 	}
 
-	ret = sysfs_create_group(&lp->dev->kobj, &lp855x_attr_group);
+	ret = sysfs_create_group(&dev->kobj, &lp855x_attr_group);
 	if (ret) {
-		dev_err(lp->dev, "failed to register sysfs. err: %d\n", ret);
+		dev_err(dev, "failed to register sysfs. err: %d\n", ret);
 		goto disable_vddio;
 	}
 
-- 
2.31.1

[PATCH 3/3] backlight: lp855x: Add support ACPI enumeration

[Hans de Goede]

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.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/video/backlight/lp855x_bl.c | 70 ++++++++++++++++++++++++-----
 1 file changed, 60 insertions(+), 10 deletions(-)

diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
index d1d27d5eb0f2..f075ec84acfb 100644
--- a/drivers/video/backlight/lp855x_bl.c
+++ b/drivers/video/backlight/lp855x_bl.c
@@ -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);
@@ -379,8 +376,31 @@ 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
+	 * so we 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 +414,20 @@ 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 +445,19 @@ 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 +577,20 @@ 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,
-- 
2.31.1

Re: [PATCH 3/3] backlight: lp855x: Add support ACPI enumeration

[Daniel Thompson]

On Mon, Nov 01, 2021 at 07:55:17PM +0100, Hans de Goede wrote:
> 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.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/video/backlight/lp855x_bl.c | 70 ++++++++++++++++++++++++-----
>  1 file changed, 60 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
> index d1d27d5eb0f2..f075ec84acfb 100644
> --- a/drivers/video/backlight/lp855x_bl.c
> +++ b/drivers/video/backlight/lp855x_bl.c
> @@ -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);

Shouldn't there be a removal of an `lp->pdata = pdata` from somewhere in
this function?


> @@ -379,8 +376,31 @@ 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

Perhaps nitpicking but ideally I'd like "and is in register mode" here 
since I presume it can also be assumed that everything with this HID
has adopted that).

Other than these, LGTM.


Daniel.

Re: [PATCH 2/3] backlight: lp855x: Add dev helper variable to lp855x_probe()

[Daniel Thompson]

On Mon, Nov 01, 2021 at 07:55:16PM +0100, Hans de Goede wrote:
> Add a dev local variable to the lp855x_probe(), to replace "&cl->dev"
> and "lp->dev" in various places.
> 
> Also switch to dev_err_probe() in one case which takes care of not
> printing -EPROBE_DEFER errors for us.
> 
> This is mostly a preparation for adding ACPI enumeration support which
> will use the new "dev" variable more.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

Re: [PATCH 1/3] backlight: lp855x: Move device_config setting out of lp855x_configure()

[Daniel Thompson]

On Mon, Nov 01, 2021 at 07:55:15PM +0100, Hans de Goede wrote:
> Move the setting of the lp->cfg pointer to the chip specific
> lp855x_device_config struct from lp855x_configure() to
> lp855x_probe(), before calling lp855x_parse_dt().
> 
> This is a preperation patch for adding ACPI enumeration support.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

Re: [PATCH 3/3] backlight: lp855x: Add support ACPI enumeration

[Hans de Goede]

Hi Daniel,

Thank you for the quick review of this series.

On 11/2/21 13:22, Daniel Thompson wrote:
> On Mon, Nov 01, 2021 at 07:55:17PM +0100, Hans de Goede wrote:
>> 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.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  drivers/video/backlight/lp855x_bl.c | 70 ++++++++++++++++++++++++-----
>>  1 file changed, 60 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
>> index d1d27d5eb0f2..f075ec84acfb 100644
>> --- a/drivers/video/backlight/lp855x_bl.c
>> +++ b/drivers/video/backlight/lp855x_bl.c
>> @@ -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);
> 
> Shouldn't there be a removal of an `lp->pdata = pdata` from somewhere in
> this function?

Ack, fixed for v2.

>> @@ -379,8 +376,31 @@ 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
> 
> Perhaps nitpicking but ideally I'd like "and is in register mode" here 
> since I presume it can also be assumed that everything with this HID
> has adopted that).

Nope not nitpicking, that is a good point, also fixed for v2.

Regards,

Hans