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gsm: add gsm0502_fn2ccch_block() 

This API is useful for checking whether a Downlink CCCH block belongs
to PCH or AGCH.  We need this API in osmo-bts.git and osmocom-bb.git.

Change-Id: I8cbd31226754e95887358ed83a928e2f567f4cf3
Related: OS#5500
This commit is contained in:
Vadim Yanitskiy 2023-06-22 23:00:05 +07:00 committed by fixeria
parent 315e78aab1
commit 418d76c2cb
3 changed files with 38 additions and 0 deletions
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2
include/osmocom/gsm/gsm0502.h
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@ -105,3 +105,5 @@ uint32_t gsm0502_fn_remap(uint32_t fn, enum gsm0502_fn_remap_channel channel);
uint16_t gsm0502_hop_seq_gen(const struct gsm_time *t,
uint8_t hsn, uint8_t maio,
size_t n, const uint16_t *ma);
int gsm0502_fn2ccch_block(uint32_t fn);

35
src/gsm/gsm0502.c
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@ -260,3 +260,38 @@ uint16_t gsm0502_hop_seq_gen(const struct gsm_time *t,
return ma ? ma[mai] : mai;
}
#define CB_FCCH -1
#define CB_SCH -2
#define CB_BCCH -3
#define CB_IDLE -4
/* Clause 7 Table 3 and Figure 8a */
static const int ccch_block_table[51] = {
CB_FCCH, CB_SCH, /* 0..1 */
CB_BCCH, CB_BCCH, CB_BCCH, CB_BCCH, /* 2..5: BCCH */
0, 0, 0, 0, /* 6..9: B0 */
CB_FCCH, CB_SCH, /* 10..11 */
1, 1, 1, 1, /* 12..15: B1 */
2, 2, 2, 2, /* 16..19: B2 */
CB_FCCH, CB_SCH, /* 20..21 */
3, 3, 3, 3, /* 22..25: B3 */
4, 4, 4, 4, /* 26..29: B4 */
CB_FCCH, CB_SCH, /* 30..31 */
5, 5, 5, 5, /* 32..35: B5 */
6, 6, 6, 6, /* 36..39: B6 */
CB_FCCH, CB_SCH, /* 40..41 */
7, 7, 7, 7, /* 42..45: B7 */
8, 8, 8, 8, /* 46..49: B8 */
CB_IDLE /* 50: Idle */
};
/*! Calculate CCCH block number from the given TDMA frame number.
* \param[in] fn TDMA frame number (of first or last burst).
* \returns CCCH block number 0..8 or a negative value,
* if the given frame number cannot carry CCCH.
*/
int gsm0502_fn2ccch_block(uint32_t fn)
{
return ccch_block_table[fn % 51];
}

1
src/gsm/libosmogsm.map
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@ -111,6 +111,7 @@ gsm0480_gen_reject;
gsm0502_calc_paging_group;
gsm0502_fn_remap;
gsm0502_hop_seq_gen;
gsm0502_fn2ccch_block;
gsm0503_xcch;
gsm0503_rach;