ACL buffer cannot be changed; and enables broken MTUs as client

[VisaJE]

/** @brief ACL Buffer size */
#define CONFIG_BT_NIMBLE_TRANSPORT_ACL_SIZE 255

In nimconfig.h this variable is not guarded, so it cannot be redefined in compile flags. I would like to understand why?

I have a problem with esp32dev and esp32-s3 platforms working as BLE clients: By setting
#define CONFIG_BT_NIMBLE_ATT_PREFERRED_MTU 512
and calling
NimBLEDevice::setMTU(CONFIG_BT_NIMBLE_ATT_PREFERRED_MTU)
I enable receiving notifications longer than the default 255, but the bytes in the notifications are nonsense beyond 255 (mostly nulls).

NimBLE version is 2.3.6, also tested 1.4.3.

I manually hacked #define CONFIG_BT_NIMBLE_TRANSPORT_ACL_SIZE 512 in the nimconfig.h and the packets seem to come through correctly.

Interestingly these issues do not exist on server side: I have another esp32-s3 communicating with the MTU==512, and at least Android platforms receive all data without issue.

[h2zero]

The fix is in the master branch, though it should be made automatic, which I will add later.

NimBLE-Arduino/src/syscfg/syscfg.h

Line 1394 in 5dad893

#ifndef MYNEWT_VAL_BLE_TRANSPORT_ACL_SIZE