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, 109 insertions, 0 deletions

diff --git a/lib/crypto/mpi/mpi-inline.h b/lib/crypto/mpi/mpi-inline.h
new file mode 100644
index 000000000..980b6b940
--- /dev/null
+++ b/lib/crypto/mpi/mpi-inline.h
@@ -0,0 +1,109 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* mpi-inline.h  -  Internal to the Multi Precision Integers
+ *	Copyright (C) 1994, 1996, 1998, 1999 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * Note: This code is heavily based on the GNU MP Library.
+ *	 Actually it's the same code with only minor changes in the
+ *	 way the data is stored; this is to support the abstraction
+ *	 of an optional secure memory allocation which may be used
+ *	 to avoid revealing of sensitive data due to paging etc.
+ *	 The GNU MP Library itself is published under the LGPL;
+ *	 however I decided to publish this code under the plain GPL.
+ */
+
+#ifndef G10_MPI_INLINE_H
+#define G10_MPI_INLINE_H
+
+#ifndef G10_MPI_INLINE_DECL
+#define G10_MPI_INLINE_DECL  static inline
+#endif
+
+G10_MPI_INLINE_DECL mpi_limb_t
+mpihelp_add_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
+	      mpi_size_t s1_size, mpi_limb_t s2_limb)
+{
+	mpi_limb_t x;
+
+	x = *s1_ptr++;
+	s2_limb += x;
+	*res_ptr++ = s2_limb;
+	if (s2_limb < x) {	/* sum is less than the left operand: handle carry */
+		while (--s1_size) {
+			x = *s1_ptr++ + 1;	/* add carry */
+			*res_ptr++ = x;	/* and store */
+			if (x)	/* not 0 (no overflow): we can stop */
+				goto leave;
+		}
+		return 1;	/* return carry (size of s1 to small) */
+	}
+
+leave:
+	if (res_ptr != s1_ptr) {	/* not the same variable */
+		mpi_size_t i;	/* copy the rest */
+		for (i = 0; i < s1_size - 1; i++)
+			res_ptr[i] = s1_ptr[i];
+	}
+	return 0;		/* no carry */
+}
+
+G10_MPI_INLINE_DECL mpi_limb_t
+mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
+	    mpi_ptr_t s2_ptr, mpi_size_t s2_size)
+{
+	mpi_limb_t cy = 0;
+
+	if (s2_size)
+		cy = mpihelp_add_n(res_ptr, s1_ptr, s2_ptr, s2_size);
+
+	if (s1_size - s2_size)
+		cy = mpihelp_add_1(res_ptr + s2_size, s1_ptr + s2_size,
+				   s1_size - s2_size, cy);
+	return cy;
+}
+
+G10_MPI_INLINE_DECL mpi_limb_t
+mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
+	      mpi_size_t s1_size, mpi_limb_t s2_limb)
+{
+	mpi_limb_t x;
+
+	x = *s1_ptr++;
+	s2_limb = x - s2_limb;
+	*res_ptr++ = s2_limb;
+	if (s2_limb > x) {
+		while (--s1_size) {
+			x = *s1_ptr++;
+			*res_ptr++ = x - 1;
+			if (x)
+				goto leave;
+		}
+		return 1;
+	}
+
+leave:
+	if (res_ptr != s1_ptr) {
+		mpi_size_t i;
+		for (i = 0; i < s1_size - 1; i++)
+			res_ptr[i] = s1_ptr[i];
+	}
+	return 0;
+}
+
+G10_MPI_INLINE_DECL mpi_limb_t
+mpihelp_sub(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
+	    mpi_ptr_t s2_ptr, mpi_size_t s2_size)
+{
+	mpi_limb_t cy = 0;
+
+	if (s2_size)
+		cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);
+
+	if (s1_size - s2_size)
+		cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
+				   s1_size - s2_size, cy);
+	return cy;
+}
+
+#endif /*G10_MPI_INLINE_H */