The patch titled
acpi/pm: traverse video_device_list for backlight restoration
has been added to the -mm tree. Its filename is
acpi-pm-traverse-video_device_list-for-backlight-restoration.patch
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Subject: acpi/pm: traverse video_device_list for backlight restoration
From: Matthias Hopf <mhopf@xxxxxxx>
acpi_video_bus_get_devices() explicitly calls
acpi_video_device_enumerate() before acpi_video_bus_get_one_device(),
which does acpi_video_device_bind().
In _enumerate(), active_list[] is created, with .bind_info explicitly set
to NULL, while the related .bind_info entry in video_device_list is set to
the acpi_video_device ptr in _bind().
The .bind_info is later used in acpi_video_resume() to re-set the
backlight - but it's only evaluated on the active_list[], on which all
.bind_info are NULL by construction. This results in backlight not being
restored, if the BIOS doesn't do this by itself already.
The patch resolves this by replacing the active_list[] traversal by a
video_device_list traversal, but due to the nature of the issue I'm unsure
whether the original issue isn't of more principal quality. I don't understand
why the list is (partially) transformed into an array in the first place,
especially as both the array *and* the list are used in the code...
.bind_info in active_list[] is NULL by construction - and used to
determine the acpi_video_device pointer during backlight restoration
during resume.
Using the list instead fixes backlight restoration for systems where the
BIOS doesn't do this by itself already.
Signed-off-by: Matthias Hopf <mhopf@xxxxxxx>
Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Matthew Garrett <mjg@xxxxxxxxxx>
Cc: Julia Lawall <julia@xxxxxxx>
Cc: Oliver Neukum <oneukum@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/acpi/video.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff -puN drivers/acpi/video.c~acpi-pm-traverse-video_device_list-for-backlight-restoration drivers/acpi/video.c
--- a/drivers/acpi/video.c~acpi-pm-traverse-video_device_list-for-backlight-restoration
+++ a/drivers/acpi/video.c
@@ -2346,7 +2346,6 @@ static int acpi_video_resume(struct noti
{
struct acpi_video_bus *video;
struct acpi_video_device *video_device;
- int i;
switch (val) {
case PM_HIBERNATION_PREPARE:
@@ -2359,11 +2358,12 @@ static int acpi_video_resume(struct noti
dev_info(&video->device->dev, "Restoring backlight state\n");
- for (i = 0; i < video->attached_count; i++) {
- video_device = video->attached_array[i].bind_info;
+ mutex_lock(&video->device_list_lock);
+ list_for_each_entry(video_device, &video->video_device_list, entry) {
if (video_device && video_device->backlight)
acpi_video_set_brightness(video_device->backlight);
}
+ mutex_unlock(&video->device_list_lock);
return NOTIFY_OK;
}
_
Patches currently in -mm which might be from mhopf@xxxxxxx are
acpi-pm-traverse-video_device_list-for-backlight-restoration.patch
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