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nimble/host: add support for Characteristic Extended Properties descriptor #2088

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nimble/host: add support for Characteristic Extended Properties descr…
piotrnarajowski Jul 25, 2025
530fc9e
nimble/host: fix coding style
piotrnarajowski Sep 3, 2025
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12 changes: 10 additions & 2 deletions nimble/host/include/host/ble_gatt.h
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Original file line number Diff line number Diff line change
Expand Up @@ -60,10 +60,13 @@ struct ble_hs_cfg;
*/

/** GATT service 16-bit UUID. */
#define BLE_GATT_SVC_UUID16 0x1801
#define BLE_GATT_SVC_UUID16 0x1801

/** GATT Client Characteristic Configuration descriptor 16-bit UUID. */
#define BLE_GATT_DSC_CLT_CFG_UUID16 0x2902
#define BLE_GATT_DSC_CLT_CFG_UUID16 0x2902

/** GATT Characteristic Extended Porperties descriptor 16-bit UUID. */
#define BLE_GATT_DSC_EXT_PROP_UUID16 0x2900

/** @} */

Expand Down Expand Up @@ -246,6 +249,11 @@ struct ble_gatt_dsc {
ble_uuid_any_t uuid;
};

/** Represents a Characteristic Extended Properties descriptor */
struct ble_gatt_cep_dsc {
/** Characteristic Extended properties **/
uint16_t properties;
};

/** Represents a handle-value tuple for multiple handle notifications. */
struct ble_gatt_notif {
Expand Down
21 changes: 15 additions & 6 deletions nimble/host/src/ble_gatt_priv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -151,13 +151,16 @@ int ble_gattc_any_jobs(void);
int ble_gattc_init(void);

/*** @server. */
#define BLE_GATTS_CLT_CFG_F_NOTIFY 0x0001
#define BLE_GATTS_CLT_CFG_F_INDICATE 0x0002
#define BLE_GATTS_CLT_CFG_F_MODIFIED 0x0080 /* Internal only. */
#define BLE_GATTS_CLT_CFG_F_RESERVED 0xfffc
#define BLE_GATTS_CLT_CFG_F_NOTIFY 0x0001
#define BLE_GATTS_CLT_CFG_F_INDICATE 0x0002
#define BLE_GATTS_CLT_CFG_F_MODIFIED 0x0080 /* Internal only. */
#define BLE_GATTS_CLT_CFG_F_RESERVED 0xfffc

#define BLE_GATTS_INC_SVC_LEN_NO_UUID 4
#define BLE_GATTS_INC_SVC_LEN_UUID 6
#define BLE_GATTS_INC_SVC_LEN_NO_UUID 4
#define BLE_GATTS_INC_SVC_LEN_UUID 6

#define BLE_GATTS_CEP_F_RELIABLE_WRITE 0x0001
#define BLE_GATTS_CEP_F_AUX_WRITE 0x0002

/**
* Contains counts of resources required by the GATT server. The contents of
Expand All @@ -183,6 +186,12 @@ struct ble_gatt_resources {
*/
uint16_t cccds;

/**
* Number of characteristic extended properties descriptors. Each of
* these also contributes to the total descriptor count.
*/
uint16_t ceps;

/** Total number of ATT attributes. */
uint16_t attrs;
};
Expand Down
105 changes: 95 additions & 10 deletions nimble/host/src/ble_gatts.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,16 +29,12 @@
#define BLE_GATTS_INCLUDE_SZ 6
#define BLE_GATTS_CHR_MAX_SZ 19

static const ble_uuid_t *uuid_pri =
BLE_UUID16_DECLARE(BLE_ATT_UUID_PRIMARY_SERVICE);
static const ble_uuid_t *uuid_sec =
BLE_UUID16_DECLARE(BLE_ATT_UUID_SECONDARY_SERVICE);
static const ble_uuid_t *uuid_inc =
BLE_UUID16_DECLARE(BLE_ATT_UUID_INCLUDE);
static const ble_uuid_t *uuid_chr =
BLE_UUID16_DECLARE(BLE_ATT_UUID_CHARACTERISTIC);
static const ble_uuid_t *uuid_ccc =
BLE_UUID16_DECLARE(BLE_GATT_DSC_CLT_CFG_UUID16);
static const ble_uuid_t *uuid_pri = BLE_UUID16_DECLARE(BLE_ATT_UUID_PRIMARY_SERVICE);
static const ble_uuid_t *uuid_sec = BLE_UUID16_DECLARE(BLE_ATT_UUID_SECONDARY_SERVICE);
static const ble_uuid_t *uuid_inc = BLE_UUID16_DECLARE(BLE_ATT_UUID_INCLUDE);
static const ble_uuid_t *uuid_chr = BLE_UUID16_DECLARE(BLE_ATT_UUID_CHARACTERISTIC);
static const ble_uuid_t *uuid_ccc = BLE_UUID16_DECLARE(BLE_GATT_DSC_CLT_CFG_UUID16);
static const ble_uuid_t *uuid_cep = BLE_UUID16_DECLARE(BLE_GATT_DSC_EXT_PROP_UUID16);

static const struct ble_gatt_svc_def **ble_gatts_svc_defs;
static int ble_gatts_num_svc_defs;
Expand Down Expand Up @@ -154,6 +150,22 @@ ble_gatts_chr_clt_cfg_allowed(const struct ble_gatt_chr_def *chr)
return flags;
}

static uint16_t
ble_gatts_chr_ext_prop_allowed(const struct ble_gatt_chr_def *chr)
{
uint16_t flags;

flags = 0;
if (chr->flags & BLE_GATT_CHR_F_RELIABLE_WRITE) {
flags |= BLE_GATTS_CEP_F_RELIABLE_WRITE;
}
if (chr->flags & BLE_GATT_CHR_F_AUX_WRITE) {
flags |= BLE_GATTS_CEP_F_AUX_WRITE;
}

return flags;
}

static uint8_t
ble_gatts_att_flags_from_chr_flags(ble_gatt_chr_flags chr_flags)
{
Expand Down Expand Up @@ -804,6 +816,55 @@ ble_gatts_register_clt_cfg_dsc(uint16_t *att_handle)
return 0;
}

static int
ble_gatts_cep_access(uint16_t conn_handle, uint16_t attr_handle, uint8_t att_op,
uint16_t offset, struct os_mbuf **om, void *arg)
{
uint16_t prop = POINTER_TO_UINT(arg);
uint8_t *buf;

ble_gatts_dsc_inc_stat(ble_gatts_dsc_op(att_op));

if (att_op != BLE_ATT_ACCESS_OP_READ) {
return BLE_ATT_ERR_WRITE_NOT_PERMITTED;
}

buf = os_mbuf_extend(*om, sizeof(prop));
if (buf == NULL) {
return BLE_ATT_ERR_INSUFFICIENT_RES;
}
put_le16(buf, prop);

return 0;
}

static int
ble_gatts_register_cep_dsc(uint16_t *att_handle, ble_gatt_chr_flags flags)
{
struct ble_gatt_cep_dsc cep;
int rc;

cep.properties = 0x0000;
if (flags & BLE_GATT_CHR_F_RELIABLE_WRITE) {
cep.properties |= BLE_GATTS_CEP_F_RELIABLE_WRITE;
}
if (flags & BLE_GATT_CHR_F_AUX_WRITE) {
/* TODO: Implement Characteristic User Description
* (Core specification 6.0, vol 3, part G, section 3.3.3.2)*/
cep.properties |= BLE_GATTS_CEP_F_AUX_WRITE;
}

rc = ble_att_svr_register(uuid_cep, BLE_ATT_F_READ, 0, att_handle,
ble_gatts_cep_access, UINT_TO_POINTER(cep.properties));
if (rc != 0) {
return rc;
}

STATS_INC(ble_gatts_stats, dscs);

return 0;
}

static int
ble_gatts_register_chr(const struct ble_gatt_svc_def *svc,
const struct ble_gatt_chr_def *chr,
Expand All @@ -814,6 +875,7 @@ ble_gatts_register_chr(const struct ble_gatt_svc_def *svc,
uint16_t def_handle;
uint16_t val_handle;
uint16_t dsc_handle;
uint16_t cep_handle;
uint8_t att_flags;
int rc;

Expand Down Expand Up @@ -870,6 +932,14 @@ ble_gatts_register_chr(const struct ble_gatt_svc_def *svc,
BLE_HS_DBG_ASSERT(dsc_handle == def_handle + 2);
}

if (ble_gatts_chr_ext_prop_allowed(chr) != 0) {
rc = ble_gatts_register_cep_dsc(&cep_handle, chr->flags);
if (rc != 0) {
return rc;
}
BLE_HS_DBG_ASSERT(cep_handle == def_handle + 3);
}

/* Register each descriptor. */
if (chr->descriptors != NULL) {
for (dsc = chr->descriptors; dsc->uuid != NULL; dsc++) {
Expand Down Expand Up @@ -2172,6 +2242,21 @@ ble_gatts_count_resources(const struct ble_gatt_svc_def *svcs,
res->attrs++;
}

/* If the characteristic permits reliable writes or auxiliary
* writes, it has an Extended Properties descriptor.
*/
if (chr->flags & BLE_GATT_CHR_F_AUX_WRITE ||
chr->flags & BLE_GATT_CHR_F_RELIABLE_WRITE) {

/* Each CEP requires:
* o 1 descriptor
* o 1 attribute
*/
res->dscs++;
res->ceps++;
res->attrs++;
}

if (chr->descriptors != NULL) {
for (d = 0; chr->descriptors[d].uuid != NULL; d++) {
if (!ble_gatts_dsc_is_sane(chr->descriptors + d)) {
Expand Down