Thread (8 messages) flat view 8 messages, 4 authors, 2007-07-24

Re: Kmalloc returns which address

From: Misbah khan <hidden>
Date: 2007-07-20 10:52:23

hi Suresh

In linux kmelloc returns the pointer to virtual address not the physical
address, to return to the physical address there is different function
called ioremap 

for eg :-
char *buf_tx =kmalloc(100,GFP_KERNEL); // Tx buffer
char *buf_rx=kmalloc(100,GFP_KERNEL); // Rx buffer

ptr_tx=ioremap( buf_tx,100);
ptr_rx=ioremap(buf_rx,100);

To learn more about this go through Linux device driver by rubini 

I hope this will work for you 
regard 
Misbah

suresh suresh wrote:
Hi,

I am porting MPC8280 driver from vxWorks to Linux.

I want know the address return by kmalloc function? is it physical address
or kernel virtual address.

For Tx and Rx, hardware uses buffers, so I have to allocate buffers and
pass
the pointer to hardware. Can I pass the pointer returned kmalloc?  or  I
should convert it into physical address?

If it returns kernel virtual address, then how to convert into physical?

Thanks & Regards-
Suresh

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