Re: POSIX.Memory_Mapping.Map_Memory

[Mark Lorenzen <mark.lorenzen@surfpost.dk>]

"Adrian Hoe" <byhoe@greenlime.com> writes:

> Florian Weimer wrote:
> > * Mark Lorenzen:
> >
> > >> I was just wondering: Is it allowed to map a device file as shared
> > >> memory? Try to use MAP_PRIVATE instead of MAP_SHARED.
> > >
> > > Furthermore: I do not think that it is possible to map character
> > > special files, since it only allows sequential access. You can
> > > probably only map block special files.
> >
> > It's possible to map /dev/zero.  In fact, there is little difference
> > between character and block devices these days.
> 
> 
> 
> Just for the purpose of recording for people who may need this in the
> future:
> 
> I've successfully mapped the memory with
> POSIX.Memory_Mapping.Map_Memory.
> 
> The VIDIOCGMBUF ioctl has to be issued before Map_Memory. This ioctl
> reports the size of buffer to Memory_Map and the offset within the
> buffer for each frame.
> 
> My application is far from completion but I have resolved this
> Memory_Map issue. I believe the wheel has just started rolling again.
> :-)
> 
> Regards,
> 
> --
> Adrian Hoe

Thanks for the info. So we can fortunately conclude that the problem
is neither Ada nor Florist related, but is simply a special issue with
this type of device.

- Mark Lorenzen