Re: Is it safe to use these Linux function (test_bit(), set_bit(), clear_bit()) in character device driver for 2.6.10 ppc kernel.

["Grant Likely" <grant.likely@secretlab.ca>]

On 10/4/07, Misbah khan <misbah_khan@engineer.com> wrote:
>
> Hi ...
> I did followed you and it worked as well. I really Thank you for it.
>
> At one Place i am doing memcpy() of floating point data to the memory mapped
> registers, what could be the substitute of it like "memcpy_toio() " which is
> suggested in the Book. I am working BE architecture.
>
> I would really appreaciate if you would let me know the defineation of these
> wrapper functions (in_be32,out_be32(),ioread32(),iowrite32(),etc) so that i
> could have the clear idea of the reason for not directly dreferencing the
> Pointer.

You don't want to directly dereference pointers to device registers
because you don't want the processor or compiler to reorder your
register accesses.  The in/out_* wrappers keeps the compiler from
reordering things, and the wrappers contain the 'sync' instruction
which prevents the processor from reordering operations at runtime.

g.
-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
grant.likely@secretlab.ca
(403) 399-0195