[PATCH 0/5] Improvements for atsam BSP and sc16is752 UART.

[Chris Johns]

On 13/02/2018 00:39, Christian Mauderer wrote:
> These patches add various improvements for the atsam BSP and for the
> sc16is752 SPI UART controller.
> 
> Regarding patch 1: Note that I have thought about an auto detection
> instead of the option. But I had a board where something responded to
> the oscillator so that I could initialize it despite the fact that no
> crystall has been connected. So I think an auto detection would be
> dangerous.

I agree with this approach.

Auto-detection is OK in systems with users however in embedded systems it is
dangerous. I have a rule, any auto-detection requires a system level module that
audits the part of a system that has auto-detection and raises any unexpected
differences as errors. Auto-detection can be hard to avoid in some systems, ie
PC motherboards, PCI etc.

I remember back in the mid-90s working on an important system with RAM size
detection where one of two static RAM chips had started to fail and the system
adjusted assuming this was all the available memory so no one noticed until many
many months into operation the application was reconfigured and it ran out of
memory when it should not have. At the start of the project I had been asked to
add the memory detection to handle different build variants of the hardware. The
feature was disabled and I have not been a fan of it ever since.

Chris