Some of the lines in `platform_mbed.h` only have `FEATURE_PSA`
checked, which is always set for Mbed OS PSA targets but the PSA
APIs are not actually available unless `FEATURE_EXPERIMENTAL_API`
is also enabled. To fix this and improve readability, group all
PSA-related lines and check both macros.
Previously we used `gettimeofday()` for Mbed TLS timing, but its
implementation provided by Mbed OS is only precise to seconds. The
microsecond component of the output `struct timeval` is always set
to zero. But Mbed TLS requires millisecond precision.
To provide required timing precision, switch to use `LowPowerTicker`
or (microsecond) `Ticker`. `LowPowerTicker` is preferred as it saves
power and Mbed TLS does not require microsecond precision.
The compiler gave redefinition warnings if
MBEDTLS_ENTROPY_HARDWARE_ALT is defined in the the compile
definitions. A check is added to prevent this warning.
Don't attempt to use default_random_seed unless both PSA and Experimental API
support are enabled. This prevents errors when the Mbed TLS NV Seed feature is
being used on platforms that have PSA enabled by default, but not Experimental
API support by default.
[DEBUG] Output: compilation terminated.
[ERROR] In file included from ./mbed-os/connectivity/mbedtls/include/mbedtls/config.h:31,
from ./mbed-os/connectivity/mbedtls/include/mbedtls/entropy.h:28,
./mbed-os/connectivity/mbedtls/platform/inc/platform_mbed.h:26:10: fatal error: default_random_seed.h: No such file or directory
26 | #include "default_random_seed.h"
Lingkai Dong
Martin Kojtal
Jaeden Amero
Bora Özgen
George Psimenos