[PATCH v5 0/1] power: Emit change uevent when updating sysfs

Abhishek Pandit-Subedi
2020-07-07T17:29:01Z

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)

Series-version 4 update:
Tested again on device and verified it's working as expected:
KERNEL[52.678174] remove /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0/bluetooth/hci0/rfkill2 (rfkill)
KERNEL[52.678211] remove /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0/bluetooth/hci0 (bluetooth)
KERNEL[52.678251] remove /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0 (usb)
KERNEL[52.679721] remove /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.1 (usb)
KERNEL[52.679772] change /devices/pci0000:00/0000:00:15.0/usb1/1-3 (usb)
KERNEL[56.022259] change /devices/pci0000:00/0000:00:15.0/usb1/1-3 (usb)
KERNEL[56.022306] add /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0 (usb)
KERNEL[56.022488] add /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0/bluetooth/hci0 (bluetooth)
KERNEL[56.022531] add /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.0/bluetooth/hci0/rfkill3 (rfkill)
KERNEL[56.023392] add /devices/pci0000:00/0000:00:15.0/usb1/1-3/1-3:1.1 (usb)

Thanks
Abhishek

Changes in v5:
- Ignore return from kobject_uevent when adding to sysfs

Changes in v4:
- Fix warning where returning from void and tested on device

Changes in v3:
- Simplified error handling

Changes in v2:
- Add newline at end of bt_dev_err

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

drivers/base/power/sysfs.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

--
2.27.0.212.ge8ba1cc988-goog