* initial implementation for Tillitis TKey device
* add UART implementation for TKey
* add Pin interface implementation for TKey touch sensor
* add RNG interface implementation for TKey
* add helpful machine package functions to return identifiers such as name and version for TKey
* use built-in timer for sleep timing on TKey
* modify UART implementation for TKey to implement Serialer interface
* implement BLAKE2s ROM function call for TKey device
* handle abort by triggering TKey device fault using illegal instruction to halt CPU
* simplify TKey implementation by inheriting from existing riscv32 target
* return error for trying to configure invalid baudrates on UART
* add tkey to builder test
* be very specific for features passed to LLVM for specific config in use for TKey
* handle feedback items from TKey device code review
Signed-off-by: deadprogram <ron@hybridgroup.com>
This function is needed for Go 1.22, and is used from various packages
like math/rand.
When there is no random number generator available, it falls back to a
static sequence of numbers. I think this is fine, because as far as I
can see it is only used for non-cryptographic needs.
All nrf chips have a cryptographically secure RNG on board. Therefore,
I've made the code more portable so that it works on all nrf chips.
I did remove a number of exported functions. I am of the opinion that
these should only be made available once we have an agreed upon API for
multiple chips. People who want to have greater control over the RNG
should use the device/nrf package directly instead.
I have also changed the behavior to always enable digital error
correction. Enabling it seems like a more conservative (and secure)
default to me. Again, people who would like to have it disabled can use
the device/nrf package directly.
The crypto/rand package is used for sensitive cryptographic operations.
Do not use the rp2040 RNG for this purpose, because it's not strong
enough for cryptography.
I think it is _possible_ to make use of the RP2040 RNG to create
cryptographically secure pseudo-random numbers, but it needs some
entropy calculation and secure hashing (blake2s or so) to make them
truly unpredictable.
Ayke van Laethem
Ron Evans
Yurii Soldak
Matt Schultz
Kenneth Bell
Olivier Fauchon