iio: proximity: vl53l0x-i2c: claim direct mode for raw readsgrafted

vl53l0x_read_raw() starts a single-shot ranging measurement and reads
back the result. Once the triggered buffer is enabled the sensor runs in
continuous mode and its data-ready interrupt is routed to the trigger,
so a concurrent in_distance_raw read disturbs the streaming setup and
never gets its completion, returning -ETIMEDOUT.

The original submission claimed direct mode here, but it was dropped
during review because the driver had no buffer support at the time [1].
Continuous (buffered) mode was later added without restoring the
claim [2], reintroducing the conflict.

Reject direct reads while buffered capture is active by claiming direct
mode around the measurement, as the vl53l1x sibling already does.

Fixes: 762186c6e7b1 ("iio: proximity: vl53l0x-i2c: Added continuous mode support")
Link: https://lore.kernel.org/linux-iio/20180911160300.GA9212@himanshu-Vostro-3559/ [1]
Link: https://lore.kernel.org/linux-iio/20240909101508.263085-3-abhashkumarjha123@gmail.com/ [2]
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/Documentation/power/shutdown-debugging.rst b/Documentation/power/shutdown-debugging.rst
new file mode 100644
index 000000000..c510122e0
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+++ b/Documentation/power/shutdown-debugging.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+Debugging Kernel Shutdown Hangs with pstore
++++++++++++++++++++++++++++++++++++++++++++
+
+Overview
+========
+If the system hangs while shutting down, the kernel logs may need to be
+retrieved to debug the issue.
+
+On systems that have a UART available, it is best to configure the kernel to use
+this UART for kernel console output.
+
+If a UART isn't available, the ``pstore`` subsystem provides a mechanism to
+persist this data across a system reset, allowing it to be retrieved on the next
+boot.
+
+Kernel Configuration
+====================
+To enable ``pstore`` and enable saving kernel ring buffer logs, set the
+following kernel configuration options:
+
+* ``CONFIG_PSTORE=y``
+* ``CONFIG_PSTORE_CONSOLE=y``
+
+Additionally, enable a backend to store the data. Depending upon your platform
+some potential options include:
+
+* ``CONFIG_EFI_VARS_PSTORE=y``
+* ``CONFIG_PSTORE_RAM=y``
+* ``CONFIG_CHROMEOS_PSTORE=y``
+* ``CONFIG_PSTORE_BLK=y``
+
+Kernel Command-line Parameters
+==============================
+Add these parameters to your kernel command line:
+
+* ``printk.always_kmsg_dump=Y``
+	* Forces the kernel to dump the entire message buffer to pstore during
+		shutdown
+* ``efi_pstore.pstore_disable=N``
+	* For EFI-based systems, ensures the EFI backend is active
+
+Userspace Interaction and Log Retrieval
+=======================================
+On the next boot after a hang, pstore logs will be available in the pstore
+filesystem (``/sys/fs/pstore``) and can be retrieved by userspace.
+
+On systemd systems, the ``systemd-pstore`` service will help do the following:
+
+#. Locate pstore data in ``/sys/fs/pstore``
+#. Read and save it to ``/var/lib/systemd/pstore``
+#. Clear pstore data for the next event