I'm exploring D for embedded work as a nice alternative to C/C++ for the 32-bitters and am finding it has a nice set of features.  But, what is the best way handle memory mapped IO?  I don't see volatile like in C. Is writing asm {} the best way to ensure memory access?

Thanks,
Dan Olson

On Sun, 09 Jan 2011 22:44:44 -0800, Dan Olson wrote:

> I'm exploring D for embedded work as a nice alternative to C/C++ for the 32-bitters and am finding it has a nice set of features.  But, what is the best way handle memory mapped IO?  I don't see volatile like in C. Is writing asm {} the best way to ensure memory access?
> 
> Thanks,
> Dan Olson

Would std.mmfile be what you need?

http://www.digitalmars.com/d/2.0/phobos/std_mmfile.html

-Lars

"Lars T. Kyllingstad" <public@kyllingen.NOSPAMnet> writes:

> On Sun, 09 Jan 2011 22:44:44 -0800, Dan Olson wrote:
>
>> I'm exploring D for embedded work as a nice alternative to C/C++ for the 32-bitters and am finding it has a nice set of features.  But, what is the best way handle memory mapped IO?  I don't see volatile like in C. Is writing asm {} the best way to ensure memory access?
>> 
>> Thanks,
>> Dan Olson
>
> Would std.mmfile be what you need?
>
> http://www.digitalmars.com/d/2.0/phobos/std_mmfile.html
>
> -Lars

Ok, thanks.  So I see that is a wrapper for mmap.  So that would be good for user space code running on top of posix or win32.  But...

I'm more interested in the general embedded case with a small OS or no
OS (just ISRs and main loop).  I'm betting without volatile, asm {} is
the next best thing for tickling a controllers peripheral registers? Yes/No?

I searched the news groups and saw there used to be a volatile.  But it looks like it was done away with because of how it was misused (like C volatile) for thread sharing.  But this is different.  This is just telling the compiler not to optimize away an access.

-- 
Dan Olson

On Mon, 10 Jan 2011 08:38:15 -0800, Dan Olson wrote:

> "Lars T. Kyllingstad" <public@kyllingen.NOSPAMnet> writes:
> 
>> On Sun, 09 Jan 2011 22:44:44 -0800, Dan Olson wrote:
>>
>>> I'm exploring D for embedded work as a nice alternative to C/C++ for the 32-bitters and am finding it has a nice set of features.  But, what is the best way handle memory mapped IO?  I don't see volatile like in C. Is writing asm {} the best way to ensure memory access?
>>> 
>>> Thanks,
>>> Dan Olson
>>
>> Would std.mmfile be what you need?
>>
>> http://www.digitalmars.com/d/2.0/phobos/std_mmfile.html
>>
>> -Lars
> 
> Ok, thanks.  So I see that is a wrapper for mmap.  So that would be good for user space code running on top of posix or win32.  But...

Ah, I should have read your post more closely.  I just saw "memory mapped IO" and latched onto that. :)


> I'm more interested in the general embedded case with a small OS or no OS (just ISRs and main loop).  I'm betting without volatile, asm {} is the next best thing for tickling a controllers peripheral registers? Yes/No?
> 
> I searched the news groups and saw there used to be a volatile.  But it looks like it was done away with because of how it was misused (like C volatile) for thread sharing.  But this is different.  This is just telling the compiler not to optimize away an access.

AFAIK, that's right.  The compiler does not optimise across asm {} blocks.

-Lars