virtual memory issue

virtual memory issue

[Ofer Rashuk]

Hi.
on my custom board with PPC8240 I'm trying to run some small user space
program.
the program tries to read a device (Galileo device) that on the PCI bus.
i configured the access to the device using mmap and got a pointer with a
virtual address.

my question is who can i translate the virtual address to a physical one.
i tried it use several functions such as virt_to_phys and virt_to_bus but i
keep getting a compilation error
target/user/include/asm-ppc/io.h:214:undefined reference to 'iopa'

what am i doing wrong, is there any lib that I'm forgetting.

my compile line is as follows:
.c.o:
	$(CC) $(CFLAGS) -c $*.c

CFLAGS	= -g -Wall -O2 -I. -D_GNU_SOURCE -D_REENTRANT

#---------------------------------------------------------------------------
-
# Make the program...
#---------------------------------------------------------------------------
-
OBJS =  \
	task.o queue.o vqueue.o event.o memblk.o timer.o sema4.o demo2.o

PROG = demo

all:	$(PROG)

$(PROG): $(OBJS) Makefile
	$(CC) $(CFLAGS) $(OBJS) -o $(PROG) -lpthread



Ofer Rashuk-Rosenthal.
Software team leader.
mailto:oferr@radlan.com


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Re: virtual memory issue

[Dan Malek]

Ofer Rashuk wrote:


> my question is who can i translate the virtual address to a physical one.

You can't from a user program, nor do you want to do this.  Using
mmap() to physical devices from a user application must be done
with great care, and is often used just for debugging purposes.  There
are resources used by the kernel and other applications that cause
race conditions you can't control.

If you need access to physical memory for any reason, you must
write a kernel device driver for this device so you can properly
manage the resources necessary to ensure proper system operation.

Thanks.


	-- Dan


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