Attention is currently required from: jolly, laforge, fixeria, dexter.

pespin has posted comments on this change. ( 
https://gerrit.osmocom.org/c/osmo-bts/+/31417 )

Change subject: l1sap: Accept RFC5993 and TS 101.318 HR GSM payload
......................................................................


Patch Set 7:

(5 comments)

Patchset:

PS7:
I'm sorry but after a more detailed look, I'm really struggling with this patch.
I think the oerall behavior is blurry and not clear.

IMHO, we should have the 2 features as you added, but they would mean "this BTS 
model supports receiving AND sending format XYZ to the upper layers".
That means a given BTS model can also support both formats.

Then, the upper layers, in the 2 paths:
- DL: MGW->MS: if the received message is of a format not supported by the BTS 
model, then it has to be converted before passing it to lower layers
- UL: MS->MGW: The BTS has a VTY command "hr-format XYZ" which specifies which 
output format to use to transmit towards the MGW. If the BTS model doesn't 
support that format, then convert it before sending to MGW.


File include/osmo-bts/bts.h:

https://gerrit.osmocom.org/c/osmo-bts/+/31417/comment/8b14f5af_ec6e53ad
PS7, Line 69:   /* Whether the BTS model uses HR GSM RTP payload in RFC 5993 
format */
To me this would be "Whether the BTS model supports sending ..."

If at some point one model supports both (which I think is expected at some 
point?) we will have a VTY command to select which one to be used.


File src/common/l1sap.c:

https://gerrit.osmocom.org/c/osmo-bts/+/31417/comment/597b8547_3992b2fa
PS7, Line 1271:                 bool rfc5993 = 
bts_internal_flag_get(lchan->ts->trx->bts, 
BTS_INTERNAL_FLAG_SPEECH_H_V1_RTP_RFC5993);
the description said the internal flag is about "sending", but iiuc you are 
using it here to decide whether the BTS model supports "receiving" it? This is 
all a bit confusing, I think the scope of the feature is not clear tbh.


https://gerrit.osmocom.org/c/osmo-bts/+/31417/comment/9ed346fa_8f252c46
PS7, Line 1274:                 if (OSMO_UNLIKELY(rfc5993 && (resp_msg->len != 
GSM_HR_BYTES_RTP_RFC5993))) {
so if the BTS supports rfc5993 (sending, receving, whatever, see previous 
comment), then you check that if the received message is not rfc5993 (aka 
potentially is  TS101.318) you are dropping it.

But it could be that a BTS supports both formats, which means in here you would 
be dropping a received pkt containing TS101.318 for a BTS which supports that 
format.


https://gerrit.osmocom.org/c/osmo-bts/+/31417/comment/de2d8768_dbad05e2
PS7, Line 1280:                         LOGPLCHAN(lchan, DL1P, LOGL_NOTICE,
There's no need for the "else" here, it is guaranteed by the early return in 
the previous if.



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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I453562da412fde5b928bd2b588129c58ec8e2a7e
Gerrit-Change-Number: 31417
Gerrit-PatchSet: 7
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