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, 98 insertions, 0 deletions

diff --git a/include/crypto/dh.h b/include/crypto/dh.h
new file mode 100644
index 000000000..7b863e911
--- /dev/null
+++ b/include/crypto/dh.h
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Diffie-Hellman secret to be used with kpp API along with helper functions
+ *
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
+ */
+#ifndef _CRYPTO_DH_
+#define _CRYPTO_DH_
+
+/**
+ * DOC: DH Helper Functions
+ *
+ * To use DH with the KPP cipher API, the following data structure and
+ * functions should be used.
+ *
+ * To use DH with KPP, the following functions should be used to operate on
+ * a DH private key. The packet private key that can be set with
+ * the KPP API function call of crypto_kpp_set_secret.
+ */
+
+/**
+ * struct dh - define a DH private key
+ *
+ * @key:	Private DH key
+ * @p:		Diffie-Hellman parameter P
+ * @g:		Diffie-Hellman generator G
+ * @key_size:	Size of the private DH key
+ * @p_size:	Size of DH parameter P
+ * @g_size:	Size of DH generator G
+ */
+struct dh {
+	const void *key;
+	const void *p;
+	const void *g;
+	unsigned int key_size;
+	unsigned int p_size;
+	unsigned int g_size;
+};
+
+/**
+ * crypto_dh_key_len() - Obtain the size of the private DH key
+ * @params:	private DH key
+ *
+ * This function returns the packet DH key size. A caller can use that
+ * with the provided DH private key reference to obtain the required
+ * memory size to hold a packet key.
+ *
+ * Return: size of the key in bytes
+ */
+unsigned int crypto_dh_key_len(const struct dh *params);
+
+/**
+ * crypto_dh_encode_key() - encode the private key
+ * @buf:	Buffer allocated by the caller to hold the packet DH
+ *		private key. The buffer should be at least crypto_dh_key_len
+ *		bytes in size.
+ * @len:	Length of the packet private key buffer
+ * @params:	Buffer with the caller-specified private key
+ *
+ * The DH implementations operate on a packet representation of the private
+ * key.
+ *
+ * Return:	-EINVAL if buffer has insufficient size, 0 on success
+ */
+int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params);
+
+/**
+ * crypto_dh_decode_key() - decode a private key
+ * @buf:	Buffer holding a packet key that should be decoded
+ * @len:	Length of the packet private key buffer
+ * @params:	Buffer allocated by the caller that is filled with the
+ *		unpacked DH private key.
+ *
+ * The unpacking obtains the private key by pointing @p to the correct location
+ * in @buf. Thus, both pointers refer to the same memory.
+ *
+ * Return:	-EINVAL if buffer has insufficient size, 0 on success
+ */
+int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params);
+
+/**
+ * __crypto_dh_decode_key() - decode a private key without parameter checks
+ * @buf:	Buffer holding a packet key that should be decoded
+ * @len:	Length of the packet private key buffer
+ * @params:	Buffer allocated by the caller that is filled with the
+ *		unpacked DH private key.
+ *
+ * Internal function providing the same services as the exported
+ * crypto_dh_decode_key(), but without any of those basic parameter
+ * checks conducted by the latter.
+ *
+ * Return:	-EINVAL if buffer has insufficient size, 0 on success
+ */
+int __crypto_dh_decode_key(const char *buf, unsigned int len,
+			   struct dh *params);
+
+#endif