Hello
I've written a simple character device driver ( that only reads and writes
from a buffer ). I'm trying to implement mmap. The code is below. The
open, release, read, write all are defined and work ok. I'm trying to map
kernel virtual address to a logical address. Only the mmap code gives
problems.
-----------< mmap >-------------------------
static int mids_mmap ( struct file * file, struct vm_area_struct *vmas )
{
unsigned long size;
if ( vmas->vm_pgoff )
return -EINVAL;
size = vmas->vm_end - vmas->vm_start;
if ( size != PAGE_SIZE )
return -EINVAL;
/* mids_buffer is defined as static char * mids_buffer and
allocated PAGE_SIZE memory in init_module()
using vmalloc()
*/
if ( remap_page_range( vmas->vm_start, virt_to_phys(mids_buffer),
size,vmas->vm_page_prot ))
return -EAGAIN;
return 0;
}
Whatever be the contents of the buffer ( i can do that using read and write
implementations ), I always get the output in the userspace code as a funny
character - ASCII value 255 ( I passed it through od ). There is no other
error.
What am I doing wrong ?
regards
Sridhar
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