[PATCH 0/1] power: Emit change uevent when updating sysfs

[PATCH 0/1] power: Emit change uevent when updating sysfs

[Abhishek Pandit-Subedi]

Hi linux-pm,

ChromeOS has a udev rule to chown the `power/wakeup` attribute so that
the power manager can modify it during runtime.

(https://source.chromium.org/chromiumos/chromiumos/codesearch/+/master:src/platform2/power_manager/udev/99-powerd-permissions.rules)

In our automated tests, we found that the `power/wakeup` attributes
weren't being chown-ed for some boards. On investigating, I found that
when the drivers probe and call device_set_wakeup_capable, no uevent was
being emitted for the newly added power/wakeup attribute. This was
manifesting at boot on some boards (Marvell SDIO bluetooth and Broadcom
Serial bluetooth drivers) or during usb disconnects during resume
(Realtek btusb driver with reset resume quirk).

It seems reasonable to me that changes to the attributes of a device
should cause a changed uevent so I have added that here.

Here's an example of the kernel events after toggling the authorized
bit of /sys/bus/usb/devices/1-3/

$ echo 0 > /sys/bus/usb/devices/1-3/authorized
KERNEL[27.357994] remove   /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0/bluetooth/hci0/rfkill1 (rfkill)
KERNEL[27.358049] remove   /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0/bluetooth/hci0 (bluetooth)
KERNEL[27.358458] remove   /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0 (usb)
KERNEL[27.358486] remove   /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.1 (usb)
KERNEL[27.358529] change   /devices/pci0000:00/0000:00:15.0/usb1/1-3 (usb)

$ echo 1 > /sys/bus/usb/devices/1-3/authorized
KERNEL[36.415749] change   /devices/pci0000:00/0000:00:15.0/usb1/1-3 (usb)
KERNEL[36.415798] add      /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0 (usb)
KERNEL[36.417414] add      /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0/bluetooth/hci0 (bluetooth)
KERNEL[36.417447] add      /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0/bluetooth/hci0/rfkill2 (rfkill)
KERNEL[36.417481] add      /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.1 (usb)

Thanks
Abhishek


Abhishek Pandit-Subedi (1):
  power: Emit changed uevent on wakeup_sysfs_add/remove

 drivers/base/power/sysfs.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

-- 
2.27.0.111.gc72c7da667-goog

[PATCH 1/1] power: Emit changed uevent on wakeup_sysfs_add/remove

[Abhishek Pandit-Subedi]

Udev rules that depend on the power/wakeup attribute don't get triggered
correctly if device_set_wakeup_capable is called after the device is
created. This can happen for several reasons (driver sets wakeup after
device is created, wakeup is changed on parent device, etc) and it seems
reasonable to emit a changed event when adding or removing attributes on
the device.

Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
---

 drivers/base/power/sysfs.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 24d25cf8ab1487..592a890bf137f0 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /* sysfs entries for device PM */
 #include <linux/device.h>
+#include <linux/kobject.h>
 #include <linux/string.h>
 #include <linux/export.h>
 #include <linux/pm_qos.h>
@@ -739,12 +740,29 @@ int dpm_sysfs_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid)
 
 int wakeup_sysfs_add(struct device *dev)
 {
-	return sysfs_merge_group(&dev->kobj, &pm_wakeup_attr_group);
+	int ret = sysfs_merge_group(&dev->kobj, &pm_wakeup_attr_group);
+
+	if (!ret) {
+		int tmp = kobject_uevent(&dev->kobj, KOBJ_CHANGE);
+
+		if (tmp)
+			dev_err(dev, "Error in uevent for wakeup_sysfs_add: %d",
+				tmp);
+	}
+
+	return ret;
 }
 
 void wakeup_sysfs_remove(struct device *dev)
 {
+	int tmp;
+
 	sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
+
+	tmp = kobject_uevent(&dev->kobj, KOBJ_CHANGE);
+	if (tmp)
+		dev_err(dev, "Error in uevent for wakeup_sysfs_remove: %d",
+			tmp);
 }
 
 int pm_qos_sysfs_add_resume_latency(struct device *dev)
-- 
2.27.0.111.gc72c7da667-goog