[PATCH v3 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

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