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The i2c-hid driver would quietly fail to probe the i2c-hid sensor-hub with an ACPI device-id of SMO91D0 every other boot. Specifically, the i2c_smbus_read_byte() "Make sure there is something at this address" check would fail every other boot. It seems that the BIOS does not properly reset/power-cycle the device leaving it in a confused state where it refuses to respond to i2c-xfers. On boots where probing the device failed, the driver-core puts the device in D3 after the probe-failure, which causes the probe to succeed the next boot. Putting the device in D3 from the shutdown-handler fixes the sensors not working every other boot. This has been tested on both a Lenovo Miix 2-10 and a Dell Venue 8 Pro 5830 both of which use an i2c-hid sensor-hub with an ACPI id of SMO91D0. Note that it is safe to call acpi_device_set_power() with a NULL pointer as first argument, so on none ACPI enumerated devices this change is a no-op. Cc: Kai-Heng Feng <kai.heng.feng@canonical.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Kai-Heng Feng <kai.heng.feng@canonical.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.