[PATCH v1 2/2] iio: light: acpi-als: Convert ACPI driver to a platform one

Posted by Rafael J. Wysocki 1 month ago

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

In all cases in which a struct acpi_driver is used for binding a driver
to an ACPI device object, a corresponding platform device is created by
the ACPI core and that device is regarded as a proper representation of
underlying hardware.  Accordingly, a struct platform_driver should be
used by driver code to bind to that device.  There are multiple reasons
why drivers should not bind directly to ACPI device objects [1].

Overall, it is better to bind drivers to platform devices than to their
ACPI companions, so convert the ACPI ambient light sensor driver to a
platform one.

After this change, the subordinate IIO device will be registered under
the platform device used for driver binding instead of its ACPI
companion.

While this is not expected to alter functionality, it changes sysfs
layout and so it will be visible to user space.

Link: https://lore.kernel.org/all/2396510.ElGaqSPkdT@rafael.j.wysocki/ [1]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/iio/light/acpi-als.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/iio/light/acpi-als.c b/drivers/iio/light/acpi-als.c
index 2fe6b493c012..ef4fe708b271 100644
--- a/drivers/iio/light/acpi-als.c
+++ b/drivers/iio/light/acpi-als.c
@@ -18,6 +18,7 @@
 #include <linux/err.h>
 #include <linux/irq.h>
 #include <linux/mutex.h>
+#include <linux/platform_device.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/buffer.h>
@@ -175,9 +176,10 @@ static irqreturn_t acpi_als_trigger_handler(int irq, void *p)
 	return IRQ_HANDLED;
 }
 
-static int acpi_als_add(struct acpi_device *device)
+static int acpi_als_probe(struct platform_device *pdev)
 {
-	struct device *dev = &device->dev;
+	struct device *dev = &pdev->dev;
+	struct acpi_device *device = ACPI_COMPANION(dev);
 	struct iio_dev *indio_dev;
 	struct acpi_als *als;
 	int ret;
@@ -188,7 +190,6 @@ static int acpi_als_add(struct acpi_device *device)
 
 	als = iio_priv(indio_dev);
 
-	device->driver_data = indio_dev;
 	als->device = device;
 	mutex_init(&als->lock);
 
@@ -226,9 +227,10 @@ static int acpi_als_add(struct acpi_device *device)
 					       acpi_als_notify, indio_dev);
 }
 
-static void acpi_als_remove(struct acpi_device *device)
+static void acpi_als_remove(struct platform_device *pdev)
 {
-	acpi_dev_remove_notify_handler(device, ACPI_DEVICE_NOTIFY, acpi_als_notify);
+	acpi_dev_remove_notify_handler(ACPI_COMPANION(&pdev->dev),
+				       ACPI_DEVICE_NOTIFY, acpi_als_notify);
 }
 
 static const struct acpi_device_id acpi_als_device_ids[] = {
@@ -238,17 +240,16 @@ static const struct acpi_device_id acpi_als_device_ids[] = {
 
 MODULE_DEVICE_TABLE(acpi, acpi_als_device_ids);
 
-static struct acpi_driver acpi_als_driver = {
-	.name	= "acpi_als",
-	.class	= ACPI_ALS_CLASS,
-	.ids	= acpi_als_device_ids,
-	.ops = {
-		.add	= acpi_als_add,
-		.remove	= acpi_als_remove,
+static struct platform_driver acpi_als_driver = {
+	.probe = acpi_als_probe,
+	.remove = acpi_als_remove,
+	.driver = {
+		.name = "acpi_als",
+		.acpi_match_table = acpi_als_device_ids,
 	},
 };
 
-module_acpi_driver(acpi_als_driver);
+module_platform_driver(acpi_als_driver);
 
 MODULE_AUTHOR("Zhang Rui <rui.zhang@intel.com>");
 MODULE_AUTHOR("Martin Liska <marxin.liska@gmail.com>");
-- 
2.51.0

Re: [PATCH v1 2/2] iio: light: acpi-als: Convert ACPI driver to a platform one

Posted by Andy Shevchenko 1 month ago

On Wed, Mar 04, 2026 at 07:33:14PM +0100, Rafael J. Wysocki wrote:
> From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> 
> In all cases in which a struct acpi_driver is used for binding a driver
> to an ACPI device object, a corresponding platform device is created by
> the ACPI core and that device is regarded as a proper representation of
> underlying hardware.  Accordingly, a struct platform_driver should be
> used by driver code to bind to that device.  There are multiple reasons
> why drivers should not bind directly to ACPI device objects [1].
> 
> Overall, it is better to bind drivers to platform devices than to their
> ACPI companions, so convert the ACPI ambient light sensor driver to a
> platform one.
> 
> After this change, the subordinate IIO device will be registered under
> the platform device used for driver binding instead of its ACPI
> companion.
> 
> While this is not expected to alter functionality, it changes sysfs
> layout and so it will be visible to user space.

...

> -static struct acpi_driver acpi_als_driver = {
> -	.name	= "acpi_als",
> -	.class	= ACPI_ALS_CLASS,
> -	.ids	= acpi_als_device_ids,
> -	.ops = {
> -		.add	= acpi_als_add,
> -		.remove	= acpi_als_remove,
> +static struct platform_driver acpi_als_driver = {
> +	.probe = acpi_als_probe,
> +	.remove = acpi_als_remove,
> +	.driver = {
> +		.name = "acpi_als",
> +		.acpi_match_table = acpi_als_device_ids,
>  	},
>  };

>  

You can also drop this unneeded blank line.

> -module_acpi_driver(acpi_als_driver);
> +module_platform_driver(acpi_als_driver);

Anyways, LGTM,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1 2/2] iio: light: acpi-als: Convert ACPI driver to a platform one

Posted by Jonathan Cameron 1 month ago

On Thu, 5 Mar 2026 09:10:49 +0200
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Wed, Mar 04, 2026 at 07:33:14PM +0100, Rafael J. Wysocki wrote:
> > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> > 
> > In all cases in which a struct acpi_driver is used for binding a driver
> > to an ACPI device object, a corresponding platform device is created by
> > the ACPI core and that device is regarded as a proper representation of
> > underlying hardware.  Accordingly, a struct platform_driver should be
> > used by driver code to bind to that device.  There are multiple reasons
> > why drivers should not bind directly to ACPI device objects [1].
> > 
> > Overall, it is better to bind drivers to platform devices than to their
> > ACPI companions, so convert the ACPI ambient light sensor driver to a
> > platform one.
> > 
> > After this change, the subordinate IIO device will be registered under
> > the platform device used for driver binding instead of its ACPI
> > companion.
> > 
> > While this is not expected to alter functionality, it changes sysfs
> > layout and so it will be visible to user space.  
> 
> ...
> 
> > -static struct acpi_driver acpi_als_driver = {
> > -	.name	= "acpi_als",
> > -	.class	= ACPI_ALS_CLASS,
> > -	.ids	= acpi_als_device_ids,
> > -	.ops = {
> > -		.add	= acpi_als_add,
> > -		.remove	= acpi_als_remove,
> > +static struct platform_driver acpi_als_driver = {
> > +	.probe = acpi_als_probe,
> > +	.remove = acpi_als_remove,
> > +	.driver = {
> > +		.name = "acpi_als",
> > +		.acpi_match_table = acpi_als_device_ids,
> >  	},
> >  };  
> 
> >    
> 
> You can also drop this unneeded blank line.
> 
> > -module_acpi_driver(acpi_als_driver);
> > +module_platform_driver(acpi_als_driver);  
> 
> Anyways, LGTM,
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tweaked and applied to the testing branch of iio.git.

Thanks,

Jonathan

>