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, 107 insertions, 0 deletions

diff --git a/Documentation/driver-api/fpga/fpga-programming.rst b/Documentation/driver-api/fpga/fpga-programming.rst
new file mode 100644
index 000000000..fb4da4240
--- /dev/null
+++ b/Documentation/driver-api/fpga/fpga-programming.rst
@@ -0,0 +1,107 @@
+In-kernel API for FPGA Programming
+==================================
+
+Overview
+--------
+
+The in-kernel API for FPGA programming is a combination of APIs from
+FPGA manager, bridge, and regions.  The actual function used to
+trigger FPGA programming is fpga_region_program_fpga().
+
+fpga_region_program_fpga() uses functionality supplied by
+the FPGA manager and bridges.  It will:
+
+ * lock the region's mutex
+ * lock the mutex of the region's FPGA manager
+ * build a list of FPGA bridges if a method has been specified to do so
+ * disable the bridges
+ * program the FPGA using info passed in :c:expr:`fpga_region->info`.
+ * re-enable the bridges
+ * release the locks
+
+The struct fpga_image_info specifies what FPGA image to program.  It is
+allocated/freed by fpga_image_info_alloc() and freed with
+fpga_image_info_free()
+
+How to program an FPGA using a region
+-------------------------------------
+
+When the FPGA region driver probed, it was given a pointer to an FPGA manager
+driver so it knows which manager to use.  The region also either has a list of
+bridges to control during programming or it has a pointer to a function that
+will generate that list.  Here's some sample code of what to do next::
+
+	#include <linux/fpga/fpga-mgr.h>
+	#include <linux/fpga/fpga-region.h>
+
+	struct fpga_image_info *info;
+	int ret;
+
+	/*
+	 * First, alloc the struct with information about the FPGA image to
+	 * program.
+	 */
+	info = fpga_image_info_alloc(dev);
+	if (!info)
+		return -ENOMEM;
+
+	/* Set flags as needed, such as: */
+	info->flags = FPGA_MGR_PARTIAL_RECONFIG;
+
+	/*
+	 * Indicate where the FPGA image is. This is pseudo-code; you're
+	 * going to use one of these three.
+	 */
+	if (image is in a scatter gather table) {
+
+		info->sgt = [your scatter gather table]
+
+	} else if (image is in a buffer) {
+
+		info->buf = [your image buffer]
+		info->count = [image buffer size]
+
+	} else if (image is in a firmware file) {
+
+		info->firmware_name = devm_kstrdup(dev, firmware_name,
+						   GFP_KERNEL);
+
+	}
+
+	/* Add info to region and do the programming */
+	region->info = info;
+	ret = fpga_region_program_fpga(region);
+
+	/* Deallocate the image info if you're done with it */
+	region->info = NULL;
+	fpga_image_info_free(info);
+
+	if (ret)
+		return ret;
+
+	/* Now enumerate whatever hardware has appeared in the FPGA. */
+
+API for programming an FPGA
+---------------------------
+
+* fpga_region_program_fpga() -  Program an FPGA
+* fpga_image_info() -  Specifies what FPGA image to program
+* fpga_image_info_alloc() -  Allocate an FPGA image info struct
+* fpga_image_info_free() -  Free an FPGA image info struct
+
+.. kernel-doc:: drivers/fpga/fpga-region.c
+   :functions: fpga_region_program_fpga
+
+FPGA Manager flags
+
+.. kernel-doc:: include/linux/fpga/fpga-mgr.h
+   :doc: FPGA Manager flags
+
+.. kernel-doc:: include/linux/fpga/fpga-mgr.h
+   :functions: fpga_image_info
+
+.. kernel-doc:: drivers/fpga/fpga-mgr.c
+   :functions: fpga_image_info_alloc
+
+.. kernel-doc:: drivers/fpga/fpga-mgr.c
+   :functions: fpga_image_info_free