linux-kernel - [PATCH] ACPI / scan: Send the change uevent with offine environmental data

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Date:   Fri,  2 Mar 2018 14:35:08 +0800
From:   "Lee, Chun-Yi" <joeyli.kernel@...il.com>
To:     "Rafael J . Wysocki" <rjw@...ysocki.net>
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Lee, Chun-Yi" <jlee@...e.com>, Michal Hocko <mhocko@...nel.org>,
        Len Brown <lenb@...nel.org>
Subject: [PATCH] ACPI / scan: Send the change uevent with offine environmental data

In current design of ACPI container offline, Kernel emits
KOBJ_CHANGE uevent to user space to indidate that the ejection of
the container was triggered by platform. (caa73ea15 patch)

A pure KOBJ_CHANGE uevent is not enough for user space to identify
the purpose. For example, a "udevadm trigger" command can also
be used to emit change event to all udev rules. A udev rule can not
identify that the event is from kernel for offline or from udevadm
for other purpose. Then the offline action in udev rule may also be
triggered by udevadm tool.

So, similar to the change uevent of dock, kernel sends the
KOBJ_CHANGE uevent with a offline environmental data to indicate
purpose. It's useful by udev rule for using ENV{EVENT} filter.

Cc: Michal Hocko <mhocko@...nel.org> 
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net> 
Cc: Len Brown <lenb@...nel.org> 
Signed-off-by: "Lee, Chun-Yi" <jlee@...e.com>
---
 drivers/acpi/scan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 8e63d93..f6dca9b 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -116,6 +116,7 @@ bool acpi_scan_is_offline(struct acpi_device *adev, bool uevent)
 {
 	struct acpi_device_physical_node *pn;
 	bool offline = true;
+	static const char *envp[] = { "EVENT=offline", NULL };

 	/*
 	 * acpi_container_offline() calls this for all of the container's
@@ -126,7 +127,7 @@ bool acpi_scan_is_offline(struct acpi_device *adev, bool uevent)
 	list_for_each_entry(pn, &adev->physical_node_list, node)
 		if (device_supports_offline(pn->dev) && !pn->dev->offline) {
 			if (uevent)
-				kobject_uevent(&pn->dev->kobj, KOBJ_CHANGE);
+				kobject_uevent_env(&pn->dev->kobj, KOBJ_CHANGE, envp);

 			offline = false;
 			break;
-- 
2.10.2