From mboxrd@z Thu Jan 1 00:00:00 1970 From: eejape@tpu.fi To: Rabeeh Khoury , linuxppc-embedded@lists.linuxppc.org Message-ID: <6142463f.463f6142@tpu.fi> Date: Thu, 09 Aug 2001 08:55:09 +0300 MIME-Version: 1.0 Subject: Re: A Question on Physical Memory Access from Applications Content-Type: text/plain; charset=iso-8859-1 Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Hi! Could you make a "short" example of this? Thanks ----- Alkuperäinen viesti ----- Lähettäjä: Rabeeh Khoury Päiväys: Torstai, Elokuu 9, 2001 0:24 Aihe: Re: A Question on Physical Memory Access from Applications > > Hi, > > We had such a problem few months ago ; what we've done is allocating > contigious physical memory using kmalloc in kernel space. > From the pointer that you get from kmalloc remove the 4 MSB bits > (usually 0xc) and pass it (some how) to the user space application. > The user space application map the address that was passed from the > kernel, and it will get another virtual contigious memory space. > > Now the memory area that you have in user space is contigious AND the > physical memory that the page tables points to is contigious > (because it > was allocated in kernel space using kmalloc), therfore it is > enough that > your ADA applications just refer to the allocated memory using a > pointerto the virtual memory. > > Regards, > Rabeeh > > > Karaaslan, Utku wrote: > > >I have ported the Linux bootloader/kernel to our home-made boards > >(Motorola 860) and they have been running well up to now. However, > >I have a problem: we've got a number of ADA applications which are > >using direct memory access to certain hardware registers. Under > >VxWorks, this is not a problem as it lacks kernelspace/userspace > >separation. Under Linux, I know I can do direct memory access > (through>/dev/mem), but in this case I want to use the > applications as they are, > >with no change to the ADA code. Is there any way to do physical > memory>access transparently wrt the application? Many thanks in > advance. > ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/