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, 82 insertions, 0 deletions

diff --git a/Documentation/bpf/maps.rst b/Documentation/bpf/maps.rst
new file mode 100644
index 000000000..6f069f3d6
--- /dev/null
+++ b/Documentation/bpf/maps.rst
@@ -0,0 +1,82 @@
+
+========
+BPF maps
+========
+
+BPF 'maps' provide generic storage of different types for sharing data between
+kernel and user space. There are several storage types available, including
+hash, array, bloom filter and radix-tree. Several of the map types exist to
+support specific BPF helpers that perform actions based on the map contents. The
+maps are accessed from BPF programs via BPF helpers which are documented in the
+`man-pages`_ for `bpf-helpers(7)`_.
+
+BPF maps are accessed from user space via the ``bpf`` syscall, which provides
+commands to create maps, lookup elements, update elements and delete elements.
+More details of the BPF syscall are available in `ebpf-syscall`_ and in the
+`man-pages`_ for `bpf(2)`_.
+
+Map Types
+=========
+
+.. toctree::
+   :maxdepth: 1
+   :glob:
+
+   map_*
+
+Usage Notes
+===========
+
+.. c:function::
+   int bpf(int command, union bpf_attr *attr, u32 size)
+
+Use the ``bpf()`` system call to perform the operation specified by
+``command``. The operation takes parameters provided in ``attr``. The ``size``
+argument is the size of the ``union bpf_attr`` in ``attr``.
+
+**BPF_MAP_CREATE**
+
+Create a map with the desired type and attributes in ``attr``:
+
+.. code-block:: c
+
+    int fd;
+    union bpf_attr attr = {
+            .map_type = BPF_MAP_TYPE_ARRAY;  /* mandatory */
+            .key_size = sizeof(__u32);       /* mandatory */
+            .value_size = sizeof(__u32);     /* mandatory */
+            .max_entries = 256;              /* mandatory */
+            .map_flags = BPF_F_MMAPABLE;
+            .map_name = "example_array";
+    };
+
+    fd = bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+
+Returns a process-local file descriptor on success, or negative error in case of
+failure. The map can be deleted by calling ``close(fd)``. Maps held by open
+file descriptors will be deleted automatically when a process exits.
+
+.. note:: Valid characters for ``map_name`` are ``A-Z``, ``a-z``, ``0-9``,
+   ``'_'`` and ``'.'``.
+
+**BPF_MAP_LOOKUP_ELEM**
+
+Lookup key in a given map using ``attr->map_fd``, ``attr->key``,
+``attr->value``. Returns zero and stores found elem into ``attr->value`` on
+success, or negative error on failure.
+
+**BPF_MAP_UPDATE_ELEM**
+
+Create or update key/value pair in a given map using ``attr->map_fd``, ``attr->key``,
+``attr->value``. Returns zero on success or negative error on failure.
+
+**BPF_MAP_DELETE_ELEM**
+
+Find and delete element by key in a given map using ``attr->map_fd``,
+``attr->key``. Returns zero on success or negative error on failure.
+
+.. Links:
+.. _man-pages: https://www.kernel.org/doc/man-pages/
+.. _bpf(2): https://man7.org/linux/man-pages/man2/bpf.2.html
+.. _bpf-helpers(7): https://man7.org/linux/man-pages/man7/bpf-helpers.7.html
+.. _ebpf-syscall: https://docs.kernel.org/userspace-api/ebpf/syscall.html