laforge has submitted this change. ( https://gerrit.osmocom.org/c/libosmo-abis/+/41209?usp=email )

Change subject: osmo_trau_frame_encode(): reduce space requirement in common case ......................................................................

osmo_trau_frame_encode(): reduce space requirement in common case

Since its introduction in 2020, osmo_trau_frame_encode() API has had the ability to emit TRAU-DL frames that are either lengthened or shortened for timing adjustment, like real TRAUs do. However, this capability was never exercised in OsmoMGW-E1, nor is it used in the new tw-e1abis-mgw: given the constraint of having to submit 160-byte blocks to the E1 stack every 20 ms, it is not really feasible for our current sw-only implementation to achieve the same 125 us timing optimizations that are possible and desirable in a hardware or FPGA implementation.

Since all current users of osmo_trau_frame_encode() API call it with fr->dl_ta_usec set to 0, the doubled output space requirement imposed by the function becomes an unnecessary burden and an API design bug in need of fixing. Solution: check fr->dir and fr->dl_ta_usec to see if frame output lengthening is actually possible for each given invocation of this function, and require doubled output space only in those cases.

Change-Id: I9f3541b0618ebef26e53b69041e5b74abefd3b85 --- M src/trau/trau_frame.c 1 file changed, 14 insertions(+), 11 deletions(-)

Approvals: Jenkins Builder: Verified fixeria: Looks good to me, but someone else must approve osmith: Looks good to me, approved

diff --git a/src/trau/trau_frame.c b/src/trau/trau_frame.c index ad7a102..d0cf3d1 100644 --- a/src/trau/trau_frame.c +++ b/src/trau/trau_frame.c @@ -1268,6 +1268,8 @@ */ int osmo_trau_frame_encode(ubit_t *bits, size_t n_bits, const struct osmo_trau_frame *fr) { + size_t space_req; + /* check for sufficient space provided by caller in output buffer */ switch (fr->type) { case OSMO_TRAU16_FT_FR: @@ -1276,35 +1278,37 @@ case OSMO_TRAU16_FT_AMR: case OSMO_TRAU16_FT_IDLE: /* timing alignment may happen: increased space requirement */ - if (n_bits < 2 * 40 * 8 - 1) - return -ENOSPC; + if (fr->dir == OSMO_TRAU_DIR_DL && fr->dl_ta_usec > 0) + space_req = 2 * 40 * 8 - 1; + else + space_req = 1 * 40 * 8; break; case OSMO_TRAU16_FT_OAM: case OSMO_TRAU16_FT_DATA_HR: case OSMO_TRAU16_FT_DATA: case OSMO_TRAU16_FT_D145_SYNC: case OSMO_TRAU16_FT_EDATA: - if (n_bits < 1 * 40 * 8) - return -ENOSPC; + space_req = 1 * 40 * 8; break; case OSMO_TRAU8_SPEECH: case OSMO_TRAU8_AMR_LOW: case OSMO_TRAU8_AMR_6k7: case OSMO_TRAU8_AMR_7k4: /* timing alignment may happen: increased space requirement */ - if (n_bits < 2 * 20 * 8 - 1) - return -ENOSPC; + if (fr->dir == OSMO_TRAU_DIR_DL && fr->dl_ta_usec > 0) + space_req = 2 * 20 * 8 - 1; + else + space_req = 1 * 20 * 8; break; case OSMO_TRAU8_DATA: case OSMO_TRAU8_OAM: - if (n_bits < 1 * 20 * 8) - return -ENOSPC; - break; - case OSMO_TRAU_FT_NONE: + space_req = 1 * 20 * 8; break; default: return -EINVAL; } + if (n_bits < space_req) + return -ENOSPC;

switch (fr->type) { case OSMO_TRAU16_FT_FR: @@ -1338,7 +1342,6 @@ return encode8_amr_67(bits, fr); case OSMO_TRAU8_AMR_7k4: return encode8_amr_74(bits, fr); - case OSMO_TRAU_FT_NONE: default: return -EINVAL; }