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

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Message-Id: <20200624210616.28477-1-abhishekpandit@chromium.org>
Date:   Wed, 24 Jun 2020 14:06:15 -0700
From:   Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
To:     linux-pm@...r.kernel.org
Cc:     linux-bluetooth@...r.kernel.org,
        chromeos-bluetooth-upstreaming@...omium.org,
        rafael.j.wysocki@...el.com, swboyd@...omium.org,
        Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Machek <pavel@....cz>
Subject: [PATCH 0/1] power: Emit change uevent when updating sysfs


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