[v1,12/16] platform/x86/thinkpad_acpi: Use acpi_dev_for_each_child()

Commit Message

Rafael J. Wysocki June 9, 2022, 2:09 p.m. UTC

From: Rafael J. Wysocki <[e-mail]>

Instead of walking the list of children of an ACPI device directly,
use acpi_dev_for_each_child() to carry out an action for all of
the given ACPI device's children.

This will help to eliminate the children list head from struct
acpi_device as it is redundant and it is used in questionable ways
in some places (in particular, locking is needed for walking the
list pointed to it safely, but it is often missing).

Signed-off-by: Rafael J. Wysocki <[e-mail]>
---
 drivers/platform/x86/thinkpad_acpi.c |   54 +++++++++++++++++++----------------
 1 file changed, 30 insertions(+), 24 deletions(-)

Comments

Andy Shevchenko June 9, 2022, 3:48 p.m. UTC | #1

On Thu, Jun 09, 2022 at 04:09:45PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <[e-mail]>
> 
> Instead of walking the list of children of an ACPI device directly,
> use acpi_dev_for_each_child() to carry out an action for all of
> the given ACPI device's children.

...

> +	rc = acpi_dev_for_each_child(device, tpacpi_evaluate_bcl, NULL);
> +	if (rc > 0)
> +		return rc;
>  
> +	return 0;

It can be simply 'return acpi_dev_for_each_child();', no?

AFAICS the caller is prepared for negative returns.

Rafael J. Wysocki June 9, 2022, 3:56 p.m. UTC | #2

On Thu, Jun 9, 2022 at 5:49 PM Andy Shevchenko
<[e-mail]> wrote:
>
> On Thu, Jun 09, 2022 at 04:09:45PM +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <[e-mail]>
> >
> > Instead of walking the list of children of an ACPI device directly,
> > use acpi_dev_for_each_child() to carry out an action for all of
> > the given ACPI device's children.
>
> ...
>
> > +     rc = acpi_dev_for_each_child(device, tpacpi_evaluate_bcl, NULL);
> > +     if (rc > 0)
> > +             return rc;
> >
> > +     return 0;
>
> It can be simply 'return acpi_dev_for_each_child();', no?

It can.

> AFAICS the caller is prepared for negative returns.

It will not return negative though unless the ACPI tables are horribly broken.

Patch

Index: linux-pm/drivers/platform/x86/thinkpad_acpi.c
===================================================================
--- linux-pm.orig/drivers/platform/x86/thinkpad_acpi.c
+++ linux-pm/drivers/platform/x86/thinkpad_acpi.c
@@ -6841,6 +6841,31 @@  static const struct backlight_ops ibm_ba
 
 /* --------------------------------------------------------------------- */
 
+static int __init tpacpi_evaluate_bcl(struct acpi_device *adev, void *not_used)
+{
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *obj;
+	acpi_status status;
+	int rc;
+
+	status = acpi_evaluate_object(adev->handle, "_BCL", NULL, &buffer);
+	if (ACPI_FAILURE(status))
+		return 0;
+
+	obj = buffer.pointer;
+	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
+		acpi_handle_info(adev->handle,
+				 "Unknown _BCL data, please report this to %s\n",
+				 TPACPI_MAIL);
+		rc = 0;
+	} else {
+		rc = obj->package.count;
+	}
+	kfree(obj);
+
+	return rc;
+}
+
 /*
  * Call _BCL method of video device.  On some ThinkPads this will
  * switch the firmware to the ACPI brightness control mode.
@@ -6848,37 +6873,18 @@  static const struct backlight_ops ibm_ba
 
 static int __init tpacpi_query_bcl_levels(acpi_handle handle)
 {
-	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
-	union acpi_object *obj;
-	struct acpi_device *device, *child;
+	struct acpi_device *device;
 	int rc;
 
 	device = acpi_fetch_acpi_dev(handle);
 	if (!device)
 		return 0;
 
-	rc = 0;
-	list_for_each_entry(child, &device->children, node) {
-		acpi_status status = acpi_evaluate_object(child->handle, "_BCL",
-							  NULL, &buffer);
-		if (ACPI_FAILURE(status)) {
-			buffer.length = ACPI_ALLOCATE_BUFFER;
-			continue;
-		}
-
-		obj = (union acpi_object *)buffer.pointer;
-		if (!obj || (obj->type != ACPI_TYPE_PACKAGE)) {
-			pr_err("Unknown _BCL data, please report this to %s\n",
-				TPACPI_MAIL);
-			rc = 0;
-		} else {
-			rc = obj->package.count;
-		}
-		break;
-	}
+	rc = acpi_dev_for_each_child(device, tpacpi_evaluate_bcl, NULL);
+	if (rc > 0)
+		return rc;
 
-	kfree(buffer.pointer);
-	return rc;
+	return 0;
 }