On Tue, 2009-07-14 at 07:41 +0800, Andrew Morton wrote:
> > acpi: don't free non-existant backlight in acpi video module
>
> "existent" :)
>
> On Sat, 11 Jul 2009 23:47:31 -0700
> keithp@xxxxxxxxxx wrote:
>
> > From: Keith Packard <keithp@xxxxxxxxxx>
> >
> > acpi_video_put_one_device was attempting to remove sysfs entries and
> > unregister a backlight device without first checking that said backlight
> > device structure had been created.
> >
> > Signed-off-by: Keith Packard <keithp@xxxxxxxxxx>
> > ---
> > drivers/acpi/video.c | 7 +++++--
> > 1 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> > index 8851315..60ea984 100644
> > --- a/drivers/acpi/video.c
> > +++ b/drivers/acpi/video.c
> > @@ -2004,8 +2004,11 @@ static int acpi_video_bus_put_one_device(struct acpi_video_device *device)
> > status = acpi_remove_notify_handler(device->dev->handle,
> > ACPI_DEVICE_NOTIFY,
> > acpi_video_device_notify);
> > - sysfs_remove_link(&device->backlight->dev.kobj, "device");
> > - backlight_device_unregister(device->backlight);
> > + if (device->backlight) {
> > + sysfs_remove_link(&device->backlight->dev.kobj, "device");
> > + backlight_device_unregister(device->backlight);
> > + device->backlight = NULL;
> > + }
> > if (device->cdev) {
> > sysfs_remove_link(&device->dev->dev.kobj,
> > "thermal_cooling");
>
> um, OK.
>
> Under which circumstances was this observed?
>
Only part of the ACPI video devices support backlight switching.
device->backlight is NULL for many ACPI video devices, like, CRT, TV,
DVI, etc.
> For symmetry we could instead test acpi_video_backlight_support() here.
>
No.
device->backlight is NULL for the devices that declare to support
backlight control while provides INVALID ACPI backlight control methods.
> The patch assumes that someone initially zeroed device->backlight. Is
> that true and reliable?
yes.
> If so, is the
>
> memset(&device->cap, 0, sizeof(device->cap));
>
> in acpi_video_device_find_cap() needed?
>
right. IMO, we can remove this.
patch attached.
thanks,
rui
device->cap and video->cap is zerod initially so we don't need
to clear it again.
Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
---
drivers/acpi/video.c | 4 ----
1 file changed, 4 deletions(-)
Index: linux-2.6/drivers/acpi/video.c
===================================================================
--- linux-2.6.orig/drivers/acpi/video.c
+++ linux-2.6/drivers/acpi/video.c
@@ -934,9 +934,6 @@ static void acpi_video_device_find_cap(s
{
acpi_handle h_dummy1;
-
- memset(&device->cap, 0, sizeof(device->cap));
-
if (ACPI_SUCCESS(acpi_get_handle(device->dev->handle, "_ADR", &h_dummy1))) {
device->cap._ADR = 1;
}
@@ -1039,7 +1036,6 @@ static void acpi_video_bus_find_cap(stru
{
acpi_handle h_dummy1;
- memset(&video->cap, 0, sizeof(video->cap));
if (ACPI_SUCCESS(acpi_get_handle(video->device->handle, "_DOS", &h_dummy1))) {
video->cap._DOS = 1;
}
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