timing interface documentation: minor clarifications
/**
* \file timing.h
*
- * \brief Portable interface to the CPU cycle counter
+ * \brief Portable interface to timeouts and to the CPU cycle counter
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
@@ -65,6 +65,9 @@ extern volatile int mbedtls_timing_alarmed;
* \warning This is only a best effort! Do not rely on this!
* In particular, it is known to be unreliable on virtual
* machines.
+ *
+ * \note This value starts at an unspecified origin and
+ * may wrap around.
*/
unsigned long mbedtls_timing_hardclock( void );
@@ -73,6 +76,8 @@ unsigned long mbedtls_timing_hardclock( void );
*
* \param val points to a timer structure
* \param reset if set to 1, the timer is restarted
+ *
+ * \return Elapsed time in ms (before the reset, if there is a reset)
*/
unsigned long mbedtls_timing_get_timer( struct mbedtls_timing_hr_time *val, int reset );
@@ -80,6 +85,7 @@ unsigned long mbedtls_timing_get_timer( struct mbedtls_timing_hr_time *val, int
* \brief Setup an alarm clock
*
* \param seconds delay before the "mbedtls_timing_alarmed" flag is set
+ * (must be >=0)
*
* \warning Only one alarm at a time is supported. In a threaded
* context, this means one for the whole process, not one per
@@ -91,11 +97,15 @@ void mbedtls_set_alarm( int seconds );
* \brief Set a pair of delays to watch
* (See \c mbedtls_timing_get_delay().)
*
- * \param data Pointer to timing data
+ * \param data Pointer to timing data.
* Must point to a valid \c mbedtls_timing_delay_context struct.
* \param int_ms First (intermediate) delay in milliseconds.
+ * The effect if int_ms > fin_ms is unspecified.
* \param fin_ms Second (final) delay in milliseconds.
* Pass 0 to cancel the current delay.
+ *
+ * \note To set a single delay, either use \c mbedtls_timing_set_timer
+ * directly or use this function with int_ms == fin_ms.
*/
void mbedtls_timing_set_delay( void *data, uint32_t int_ms, uint32_t fin_ms );
@@ -106,7 +116,7 @@ void mbedtls_timing_set_delay( void *data, uint32_t int_ms, uint32_t fin_ms );
* \param data Pointer to timing data
* Must point to a valid \c mbedtls_timing_delay_context struct.
*
- * \return -1 if cancelled (fin_ms = 0)
+ * \return -1 if cancelled (fin_ms = 0),
* 0 if none of the delays are passed,
* 1 if only the intermediate delay is passed,
* 2 if the final delay is passed.
