Re: Linux kernel 2.6.x Raw device support
Dave Platt <email@example.com> wrote:
> > I believe that the reason for not implementing raw devices on Linux was the fact
> > that Linux was designed for x86 and the way Linux did implement DMA to devices
> > would have made a raw device slower than a buffered device.
> I believe that your belief is entirely wrong.
So please proove...
> I've used the (2.2 and 2.4) /dev/raw/* version of Linux raw devices
> for several years now, to create a high-speed disk duplication system.
> It runs on commodity X86 hardware, using off-the-shelf PCI-bus UDMA
> IDE controllers.
I've never seen /dev/raw/* on a Linux-2.4 system.
I did however check the linux kernel-2.2 sources because I was trying
to implement a better SCSI Generic driver that time. If the Linux
kernel has been able to do user mode DMA, then there was no need to
allocate a special DMA buffer inside the kernel and to use copyout
(or it's Linux equivalent) later to move the data to userland.