In particular, this makes the L4 .isr_vector section 16K in size so it's
the same as the F4/F7 MCUs. The patch also moves the L4 filesystem to
the end of flash, which allows for 512K filesystem on the 1Mb devices
like the STM32L476DISC.
The delay_half parameter must be specified by the port to set up the
timing of the software SPI. This allows the port to adjust the timing
value to better suit its timing characteristics, as well as provide a
more accurate printing of the baudrate.
It's simpler to just default to always using software SPI if no specific
peripheral id/name is given. To use hardware SPI users must specify a
hardware peripheral id as the first parameter to the SPI constructor.
There is no need to take src_len and dest_len arguments. The case of
reading-only with a single output byte (originally src_len=1, dest_len>1)
is now handled by using the output buffer as the input buffer, and using
memset to fill the output byte into this buffer. This simplifies the
implementations of the spi_transfer protocol function.
Similar to how binary op already works. Common unary operations already
have fast paths for bool so there's no need to have explicit handling of
ops in bool_unary_op, especially since they have the same behaviour as
integers.