Re: [avr-libc-dev] eeproms and interrupts

[Bernard Fouché]

Joerg Wunsch wrote:

> I'd even go so far to write it in the preamble that unless explicitly
> stated, none of the library functions claims interrupt-safety.
>
> Any opinions about that?
>
>  
Well there are not re-entrant but interrupt safe, even for eeprom access 
since eeprom_write_* blocks
interrupts correctly.

I was not sure about eeprom read, and "brberie" comments and Atmel 
documentation confused me
about that. Atmel writes, before eeprom read examples "The next code 
examples show assembly and C functions for reading the EEPROM. The 
examples assume that interrupts are controlled so that no interrupts 
will occur during execution of these functions." (Documentation of 
atmega64 2490J-AVR-03/05, page 23). So strictly reading that, one can 
think that even for eeprom read, it is mandatory to lock interrupts. 
However reading how to use EERE page 21, there is nothing about 
interrupts...

Now doing like you wrote, one should spend time specifying that a lot of 
functions are interrupt safe, when, in fact, only a small bunch are 
interrupt sensitive. Why not having something like: "All functions are 
interrupt safe but may not be re-entrant. The user is advised to read 
Atmel documentation about features directly related to hardware like 
eeprom or flash write for instance."

And then the 'user' would be confused like I was ;-) Unless eeprom reads 
really need interrupt protection!

 Bernard