consider we're writing a firmware for a baremetal MCU, i.e. no OS. I'm told it's not possible (illegal?) to pass arguments to interrupt handler function?
I can't precisely understand why it is so? What's wrong with this?
PS. is it possible to do in some RTOS-es, embedded Linux etc. or it si fundamentally wrong ?
The only other thing I'll point out (that hasn't been mentioned so far) is the concept of a "software interrupt" (sometimes called a "trap"), which most processors support.
The idea is that a special instruction causes an exception to take place, and often with a software interrupt, either the opcode causing the exception, or registers set up prior to the exception, can contain values/arguments.
For example, in ARM processors, look up "SWI" or "SVC", depending on your architecture. I believe with the SWI instruction, the lower 8 bits are not part of the opcode - you can fill in whatever you want & pass a value from 0-255 (memory a little fuzzy here).
Unlike a hardware-initiated interrupt, which is totally asynchronous to the code running on the CPU, a software interrupt is synchronous - it occurs when the initiating instruction is executed (barring interrupt masking, nesting, etc.)