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, 71 insertions, 0 deletions

diff --git a/Documentation/tee/ts-tee.rst b/Documentation/tee/ts-tee.rst
new file mode 100644
index 000000000..843e34422
--- /dev/null
+++ b/Documentation/tee/ts-tee.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+=================================
+TS-TEE (Trusted Services project)
+=================================
+
+This driver provides access to secure services implemented by Trusted Services.
+
+Trusted Services [1] is a TrustedFirmware.org project that provides a framework
+for developing and deploying device Root of Trust services in FF-A [2] S-EL0
+Secure Partitions. The project hosts the reference implementation of the Arm
+Platform Security Architecture [3] for Arm A-profile devices.
+
+The FF-A Secure Partitions (SP) are accessible through the FF-A driver [4] which
+provides the low level communication for this driver. On top of that the Trusted
+Services RPC protocol is used [5]. To use the driver from user space a reference
+implementation is provided at [6], which is part of the Trusted Services client
+library called libts [7].
+
+All Trusted Services (TS) SPs have the same FF-A UUID; it identifies the TS RPC
+protocol. A TS SP can host one or more services (e.g. PSA Crypto, PSA ITS, etc).
+A service is identified by its service UUID; the same type of service cannot be
+present twice in the same SP. During SP boot each service in the SP is assigned
+an "interface ID". This is just a short ID to simplify message addressing.
+
+The generic TEE design is to share memory at once with the Trusted OS, which can
+then be reused to communicate with multiple applications running on the Trusted
+OS. However, in case of FF-A, memory sharing works on an endpoint level, i.e.
+memory is shared with a specific SP. User space has to be able to separately
+share memory with each SP based on its endpoint ID; therefore a separate TEE
+device is registered for each discovered TS SP. Opening the SP corresponds to
+opening the TEE device and creating a TEE context. A TS SP hosts one or more
+services. Opening a service corresponds to opening a session in the given
+tee_context.
+
+Overview of a system with Trusted Services components::
+
+   User space                  Kernel space                   Secure world
+   ~~~~~~~~~~                  ~~~~~~~~~~~~                   ~~~~~~~~~~~~
+   +--------+                                               +-------------+
+   | Client |                                               | Trusted     |
+   +--------+                                               | Services SP |
+      /\                                                    +-------------+
+      ||                                                          /\
+      ||                                                          ||
+      ||                                                          ||
+      \/                                                          \/
+   +-------+                +----------+--------+           +-------------+
+   | libts |                |  TEE     | TS-TEE |           |  FF-A SPMC  |
+   |       |                |  subsys  | driver |           |   + SPMD    |
+   +-------+----------------+----+-----+--------+-----------+-------------+
+   |      Generic TEE API        |     |  FF-A  |     TS RPC protocol     |
+   |      IOCTL (TEE_IOC_*)      |     | driver |        over FF-A        |
+   +-----------------------------+     +--------+-------------------------+
+
+References
+==========
+
+[1] https://www.trustedfirmware.org/projects/trusted-services/
+
+[2] https://developer.arm.com/documentation/den0077/
+
+[3] https://www.arm.com/architecture/security-features/platform-security
+
+[4] drivers/firmware/arm_ffa/
+
+[5] https://trusted-services.readthedocs.io/en/v1.0.0/developer/service-access-protocols.html#abi
+
+[6] https://git.trustedfirmware.org/TS/trusted-services.git/tree/components/rpc/ts_rpc/caller/linux/ts_rpc_caller_linux.c?h=v1.0.0
+
+[7] https://git.trustedfirmware.org/TS/trusted-services.git/tree/deployments/libts/arm-linux/CMakeLists.txt?h=v1.0.0