On 25.01.2019 20:07, Andrew Lunn wrote: >> Andrew, for my understanding: What do you think is wrong with the >> alignment requirement? It was introduced because we do a 32 bit access >> to the start address of the array and want to avoid an unaligned access. > > Hi Heiner > > Because you are doing pointer aliasing, the compiler will by default > generate bad code, doing unaligned access. Adding the attribute works > around this. But it is just a work around. Since this is very slow > path code, i would just avoid the pointer aliasing, write a bit more C > code as Thierry suggested, and the optimiser will probably figure out > what is going on and produce reasonable code. > > Also, in general, by avoiding pointer aliasing, you allow static code > checkers to work better. They are more likely to discover buffer > overruns, etc. > > Andrew > Thanks, good to know. The following doesn't hurt us here, but things like this have to be considered too. According to chip spec: "The ID registers 0-5 are only permitted to write by 4-byte access. Read access can be byte, word, or double word access." Heiner
