Attention is currently required from: neels, pespin, dexter.
fixeria has posted comments on this change. (
https://gerrit.osmocom.org/c/libosmocore/+/29475 )
Change subject: fix gsm0808_sc_cfg <-> gsm48_mr_cfg conversion
......................................................................
Patch Set 4:
(1 comment)
File include/osmocom/gsm/protocol/gsm_04_08.h:
https://gerrit.osmocom.org/c/libosmocore/+/29475/comment/65ec494f_715300db
PS2, Line 627: return ((uint8_t *)cfg)[1];
gsm48_multi_rate_conf has two uint8_t members, AFAICT
adding a union would require adding another ex […]
You don't really need to name
the union itself, it can be anonymous (just like structures). The problem is that
bit-fields are treated as individual fields in a union, so doing what Pau suggested:
```
/* I removed the LE variant for the sake of readability
* see
https://people.osmocom.org/fixeria/union_bfield_test.c */
struct gsm48_multi_rate_conf {
uint8_t ver:3, nscb:1, icmi:1, spare:1, smod:2;
union {
uint8_t m12_2:1, m10_2:1, m7_95:1, m7_40:1,
m6_70:1, m5_90:1, m5_15:1, m4_75:1;
uint8_t mode;
};
} __attribute__((packed));
```
will result in the following behavior:
```
struct gsm48_multi_rate_conf mrc = { 0 };
// mrc.mode = 0x00
// m4_75=0, m5_15=0, m5_90=0, m6_70=0, m7_40=0, m7_95=0, m10_2=0, m12_2=0
mrc.m4_75 = 1;
// mrc.mode = 0x01
// m4_75=1, m5_15=1, m5_90=1, m6_70=1, m7_40=1, m7_95=1, m10_2=1, m12_2=1
mrc.m10_2 = 0;
// mrc.mode = 0x00
// m4_75=0, m5_15=0, m5_90=0, m6_70=0, m7_40=0, m7_95=0, m10_2=0, m12_2=0
mrc.m12_2 = 1;
// mrc.mode = 0x01
// m4_75=1, m5_15=1, m5_90=1, m6_70=1, m7_40=1, m7_95=1, m10_2=1, m12_2=1
```
Definitely not what we want. Here is an alternative approach:
```
union gsm48_multi_rate_conf_u {
struct gsm48_multi_rate_conf mrc;
struct {
uint8_t hdr;
uint8_t mode;
};
};
```
This should work as expected, but I am fine with the current approach. Keep it as it is.
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Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Change-Id: I900fda192742fa8f6dd54e9131ef1704b14cc41a
Gerrit-Change-Number: 29475
Gerrit-PatchSet: 4
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