Re: [PATCH] ACPI: dock: Don't eval _STA on every show_docked sysfs read

[Holger Macht <hmacht@suse.de>]

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Hi,

sorry for the delay...

On Tue, 2009-01-27 at 13:04 -0800, Andrew Morton wrote:
> On Tue, 20 Jan 2009 12:18:24 +0100
> Holger Macht <hmacht@suse.de> wrote:
> 
> > Cc: stable@kernel.org
> 
> The patch applied OK to 2.6.28 but not to any earlier kernel.  If we
> decide that it should be backported to 2.6.27 or earlier, a new patch
> might be needed for that.

Patch that applies to stable kernel from today is attached.

Thanks,
	Holger

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Some devices trigger a DEVICE_CHECK on every evalutation of _STA. This
can also be seen in commit 8b59560a3baf2e7c24e0fb92ea5d09eca92805db
(acpi: dock: avoid check _STA method).  If an undock is processed, the
dock driver sends a uevent and userspace might read the show_docked
property in sysfs. This causes an evaluation of _STA of the particular
device which causes the dock driver to immediately dock again.

In any case, evaluation of _STA (show_docked) does not necessarily mean
that we are docked, so check with the internal device structure.

http://bugzilla.kernel.org/show_bug.cgi?id=12360

Signed-off-by: Holger Macht <hmacht@suse.de>
---

diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
index 25d2161..7290e54 100644
--- a/drivers/acpi/dock.c
+++ b/drivers/acpi/dock.c
@@ -691,8 +691,14 @@ fdd_out:
 static ssize_t show_docked(struct device *dev,
 			   struct device_attribute *attr, char *buf)
 {
-	return snprintf(buf, PAGE_SIZE, "%d\n", dock_present(dock_station));
+	struct acpi_device *tmp;
+
+	struct dock_station *dock_station = *((struct dock_station **)
+		dev->platform_data);
 
+	if (ACPI_SUCCESS(acpi_bus_get_device(dock_station->handle, &tmp)))
+		return snprintf(buf, PAGE_SIZE, "1\n");
+	return snprintf(buf, PAGE_SIZE, "0\n");
 }
 static DEVICE_ATTR(docked, S_IRUGO, show_docked, NULL);