On Tue, 20 Feb 2001, Norbert Roos wrote:
> Jeff Garzik wrote:
>
> > > But the buffers are usually allocated with malloc() by any application
> > > which wants to use my driver.. otherwise my driver would have to offer a
> > > malloc-like function, but I can hardly force the application to use my
> > > own malloc function.
> >
> > If you are writing the driver, sure you can.
>
> ??
>
> The application is doing something like
>
> fd = open("/dev/mydriver");
> buf = malloc();
> fill_buffer_with_data(buf);
> write(fd,buf);
>
> And now i should tell the programmer not to use malloc() but my special
> driver-malloc?
> Or do you mean something different?
fd = open(...);
buf = mmap(fd, ...);
fill_buffer_with_data(buf);
ioctl(fd, ...); /* tell kernel data is there */
There are variations depending on the application, but you get the
picture. A buffer copy is eliminated when mmap is used, too, making
your application faster.
Jeff
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