CPU IDs may contain very little entropy. Often only a single byte
may change between two CPUs.
To mitigate this use a somewhat 'proper' hash algorithm (I chose DJB2
hash simply because it's small) and 'extend' it to the required output
size.
For 50 STM32 CPU IDs from the grenoble site, this produces a much more
random LUID output.
Booleans make sense for dimmers when accessed from a Sith application
that deals in absolutes.
Percent values are also a widespread interpretation of brightness
levels, and are thus supported as well.
The bit arithmetic makes sure that the arithmetic operation value / 100
* saul_pwm_resolution is done efficiently (by expression as a
multiplication followed by shifting) and accurately (by maximizing the
number of usable bits) while still being flexible both with respect to
integer sizes and to changes of saul_pwm_resolution.
Co-authored-by: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
In analogy to the existing GPIO mappings, this provides (write-only)
SAUL entries for PWM'd LEDs in a single-LED (as SAUL_ACT_DIMMER) and an
RGB (as SAUL_ACT_RGB_LED) mode.
Co-authored-by: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
When enabling & disabling interrupts back-to-back pending interrupts
are not serviced on Cortex-M23/M33.
Flush the pipeline to give interrupts a chance of executing in `sched_arch_idle()`.
This fixes `no_idle_thread` on Cortex-M23.
The RISC-V toolchain in riotdocker has issues with picolibc and
will still include newlib headers.
This leads to conflicts like
```
In file included from [01m[Knanostubs.c:22[m[K:
[01m[K/usr/local/picolibc/riscv-none-embed/include/stdio.h:270:23:[m[K [01;31m[Kerror: [m[Kconflicting types for '[01m[K__FILE[m[K'
typedef struct __file [01;31m[K__FILE[m[K;
[01;31m[K^~~~~~[m[K
In file included from [01m[K/opt/gnu-mcu-eclipse/riscv-none-gcc/8.2.0-2.2-20190521-0004/riscv-none-embed/include/reent.h:93[m[K,
from [01m[Knanostubs.c:20[m[K:
[01m[K/opt/gnu-mcu-eclipse/riscv-none-gcc/8.2.0-2.2-20190521-0004/riscv-none-embed/include/sys/reent.h:287:26:[m[K [01;36m[Knote: [m[Kprevious declaration of '[01m[K__FILE[m[K' was here
typedef struct __sFILE [01;36m[K__FILE[m[K;
[01;36m[K^~~~~~[m[K
```
The problem does not occur when installing both the toolchain and picolibc
directly from the Debian / Ubuntu repositories, but CI uses an older Ubuntu
version that does not have those packages yet, so it builds them manually.
Blacklist RISC-V until CI has been updated.
