update/extend doxygen documentation

It's a pity that even with this patch we still are fare away from having
the whole API documented.  However, at least we have a more solid
foundation.  Updates not only extend the documentation, but also make
sure it is rendered properly in the doxygen HTML.

Change-Id: I1344bd1a6869fb00de7c1899a8db93bba9bafce3
diff --git a/src/gsm/gsm_04_08_gprs.c b/src/gsm/gsm_04_08_gprs.c
index 5fef208..bd986d7 100644
--- a/src/gsm/gsm_04_08_gprs.c
+++ b/src/gsm/gsm_04_08_gprs.c
@@ -26,9 +26,11 @@
 
 #include <stdbool.h>
 
-/* Protocol related stuff, should go into libosmocore */
+/*! \addtogroup gsm0408
+ *  @{
+ */
 
-/* 10.5.5.14 GPRS MM Cause / Table 10.5.147 */
+/*! \brief 10.5.5.14 GPRS MM Cause / Table 10.5.147 */
 const struct value_string gsm48_gmm_cause_names_[] = {
 	{ GMM_CAUSE_IMSI_UNKNOWN,	"IMSI unknown in HLR" },
 	{ GMM_CAUSE_ILLEGAL_MS,		"Illegal MS" },
@@ -73,7 +75,7 @@
 
 const struct value_string *gsm48_gmm_cause_names = gsm48_gmm_cause_names_;
 
-/* 10.5.6.6 SM Cause / Table 10.5.157 */
+/*! \brief 10.5.6.6 SM Cause / Table 10.5.157 */
 const struct value_string gsm48_gsm_cause_names_[] = {
 	{ GSM_CAUSE_OPER_DET_BARR, "Operator Determined Barring" },
 	{ GSM_CAUSE_MBMS_CAP_INSUF, "MBMS bearer capabilities insufficient for the service" },
@@ -140,6 +142,7 @@
 	}
 }
 
+/*! \brief String names of GMM message types */
 const struct value_string gprs_msgt_gmm_names[] = {
 	{ GSM48_MT_GMM_ATTACH_REQ,		"ATTACH REQUEST" },
 	{ GSM48_MT_GMM_ATTACH_ACK,		"ATTACH ACK" },
@@ -164,7 +167,7 @@
 	{ 0, NULL }
 };
 
-/* 10.5.5.2 */
+/*! \brief String names of GPRS Attach types according to 10.5.5.2 */
 const struct value_string gprs_att_t_strs_[] = {
 	{ GPRS_ATT_T_ATTACH,		"GPRS attach" },
 	{ GPRS_ATT_T_ATT_WHILE_IMSI,	"GPRS attach while IMSI attached" },
@@ -174,6 +177,7 @@
 
 const struct value_string *gprs_att_t_strs = gprs_att_t_strs_;
 
+/*! \brief String names of GPRS Location Update Types */
 const struct value_string gprs_upd_t_strs_[] = {
 	{ GPRS_UPD_T_RA,		"RA updating" },
 	{ GPRS_UPD_T_RA_LA,		"combined RA/LA updating" },
@@ -184,7 +188,7 @@
 
 const struct value_string *gprs_upd_t_strs = gprs_upd_t_strs_;
 
-/* 10.5.5.5 */
+/*! \brief String names of GMM MO Detach Types according to 10.5.5.5 */
 const struct value_string gprs_det_t_mo_strs_[] = {
 	{ GPRS_DET_T_MO_GPRS,		"GPRS detach" },
 	{ GPRS_DET_T_MO_IMSI,		"IMSI detach" },
@@ -194,6 +198,7 @@
 
 const struct value_string *gprs_det_t_mo_strs = gprs_det_t_mo_strs_;
 
+/*! \brief String names of GMM MT Detach Types according to 10.5.5.5 */
 const struct value_string gprs_det_t_mt_strs_[] = {
 	{ GPRS_DET_T_MT_REATT_REQ,	"re-attach required" },
 	{ GPRS_DET_T_MT_REATT_NOTREQ,	"re-attach not required" },
@@ -203,6 +208,7 @@
 
 const struct value_string *gprs_det_t_mt_strs = gprs_det_t_mt_strs_;
 
+/*! \brief String names of GMM Service Types */
 const struct value_string gprs_service_t_strs_[] = {
 	{ GPRS_SERVICE_T_SIGNALLING,	"signalling" },
 	{ GPRS_SERVICE_T_DATA,		"data" },
@@ -213,3 +219,5 @@
 };
 
 const struct value_string *gprs_service_t_strs = gprs_service_t_strs_;
+
+/*! @} */