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gsm0502: add TDMA frame number constants and modular arithmetic 

These TDMA constatns and modular arithmetic operations are used in
a number of osmo-* projects, so it makes sense to have them all
in a single header file, with minimalistic documentation.

Change-Id: Ic291fd3644f34964374227a191c7045d79d77e0d
This commit is contained in:
Vadim Yanitskiy 2020-06-17 03:55:46 +07:00 committed by laforge
parent 30856ca5cb
commit ed0445b38b
1 changed files with 24 additions and 0 deletions
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24
include/osmocom/gsm/gsm0502.h
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@ -7,6 +7,30 @@
#include <osmocom/gsm/protocol/gsm_04_08.h>
#include <osmocom/gsm/protocol/gsm_08_58.h>
/* 4.3.3 TDMA frame number : constants and modular arithmetic */
#define GSM_TDMA_FN_DURATION_nS 4615384 /* in 1e−9 seconds (approx) */
#define GSM_TDMA_FN_DURATION_uS 4615 /* in 1e-6 seconds (approx) */
#define GSM_TDMA_SUPERFRAME (26 * 51)
#define GSM_TDMA_HYPERFRAME (2048 * GSM_TDMA_SUPERFRAME)
/*! Return the sum of two specified TDMA frame numbers (summation) */
#define GSM_TDMA_FN_SUM(a, b) \
((a + b) % GSM_TDMA_HYPERFRAME)
/*! Return the difference of two specified TDMA frame numbers (subtraction) */
#define GSM_TDMA_FN_SUB(a, b) \
((a + GSM_TDMA_HYPERFRAME - b) % GSM_TDMA_HYPERFRAME)
/*! Return the *minimum* difference of two specified TDMA frame numbers (distance) */
#define GSM_TDMA_FN_DIFF(a, b) \
OSMO_MIN(GSM_TDMA_FN_SUB(a, b), GSM_TDMA_FN_SUB(b, a))
/*! Increment the given TDMA frame number by 1 and return the result (like ++fn) */
#define GSM_TDMA_FN_INC(fn) \
((fn) = GSM_TDMA_FN_SUM((fn), 1))
/*! Decrement the given TDMA frame number by 1 and return the result (like --fn) */
#define GSM_TDMA_FN_DEC(fn) \
((fn) = GSM_TDMA_FN_SUB((fn), 1))
/* Table 5 Clause 7 TS 05.02 */
static inline unsigned int
gsm0502_get_n_pag_blocks(struct gsm48_control_channel_descr *chan_desc)