Receiving an empty string in an RPC call currently panics.
When `length` is zero, a call to the `alloc` function (as implemented in `artiq/firmware/runtime/session.rs`) returns a null pointer. Constructing a `CMutSlice` from a null pointer panics.
A `CMutSlice` consists of a pointer and the length. Rust's documentation of the `core::ptr` module states: "The canonical way to obtain a pointer that is valid for zero-sized accesses is `NonNull::dangling`."
This commits adds a check for the length of a string received in an RPC call. Only for lengths greater than zero a memory allocation is performed. For zero-length strings, a dangling pointer is used.
Test plan:
Invoke the following experiment, which returns an empty string over RPC:
```
class ReturnEmptyString(artiq.experiment.EnvExperiment):
def build(self):
self.core: Core = self.get_device("core")
@kernel
def run(self):
x = self.do_rpc()
print(x)
@rpc
def do_rpc(self) -> TStr:
return ""
```
Signed-off-by: Sven Over (Oxford Ionics) <sven.over@oxionics.com>
Change initialization behaviour of GTX transceivers
--
Modify the config parms CPLL of GTX transceiver for PLL to lock correctly
Modify the enabling requirement of GTX input clock buffer IBUFDS_GTE2 so
that it depends on GTX PLL locked signal instead of TX Init Done
Modify the GTX Init FSM so that BruteForceClock Aligner can reset GTX
transceiver without resetting the GTX transceiver PLL
kasli-soc: fix of SYS CLK switch failure
Changed initialization of GTX transceivers.
Successful SYS CLK switching requires IBUFDS_GTE2 to be properly enabled and not disabled during GTX transceiver initialization.
For this reason, CPLL is not reset during GTX initialization and clock alignment.
kasli-soc: refractor fix of SYS CLK switch failure
Remove gtXxreset & cpllreset assertion and deassertion
The removed code does not affect the fix
