Andrea Gasparini wrote, Friday, September 23, 2011:
> Hi,
> I'm having some problem understanding how mmap really works, I'm on a
> DM365, with a 2.6.32 kernel.
>
> I have a (dummy) driver that allocate some memory (4k), and gives it to
> a userspace through mmap() - the usual remap_pfn_range found in every
> example.
> i.e. using this:
> if (remap_pfn_range(vma, vma->vm_start,
> virt_to_phys(buffer) >> PAGE_SHIFT,
> vma->vm_end - vma->vm_start,
> vma->vm_page_prot)){
> printk("remap returned something wrong\n");
> return -EAGAIN;
>
> The userspace can read the memory correctly, but can't write to it.
> (though it maps with PROT_WRITE)
> As the manpage says: PROT_WRITE - Pages may be written.
>
> I'm attaching both the driver and the userspace testbed, with the hope
> someone tells me what's wrong with this.
Ok, if opened with O_RDWR (and not read-only) and mapped with MAP_SHARED it
works ...
sorry fror the silly question :)
Bye.
--
Andrea Gasparini
---- ImaVis S.r.l. ----
web: www.imavis.com
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