Re: From: Carlos Mart??n <carlos@cmartin.tk>

["Carlos Martín" <carlos@cmartin.tk>]

On Tuesday 21 February 2006 21:32, Christoph Hellwig wrote:
> On Tue, Feb 21, 2006 at 09:24:23PM +0100, Carlos Mart?n wrote:
> > Wouldn't this lead to duplicated function definitions at link time if both 
are 
> > compiled-in? From your module split above I understood you wanted 
acx-common 
> > to be another module, but here I see it goes into the modules.
> > 
> 
> No.  The above makefile fragment builds three modules: acx-common.o,
> acx-pci.o and acx-usb.o as mentioned above.  The magic here is that with
> that makefile fragment is that the kbuild systems builds acx-common.o if
> either CONFIG_ACX_PCI or CONFIG_ACX_USB is set, and even makes sure to
> do the right thing if either is builtin.  There is not code duplication
> at all.

Then all is good.

> 
> > > ---- snip ----
> > > 
> > >  - kill the IS_PCI/IS_USB macros and add a acx_operations structure that
> > >    handles the different hardware without branches all over and allows
> > >    the hw-specific code to be in separate modules.
> > 
> > There aren't that many IS_{PCI,USB} uses and most if not all are justified 
> > (extra step for one case). It might be a good idea to do that for the 
> > IS_ACX{100,111} macros instead of calling the generic function which then 
> > calls the chip-specific one.
> 
> The important bit is that you need the pointers with the above module
> spit, because you can't call usb- or pci-specific routines from 
> acx-common.ko 

Yes, I realise that (unless you export them, but I don't think we want that). 
I've started this, but I think it'll probably be next week before I have time 
to really work on it.

This approach is probably better even if the driver is unified. Pointer 
dereferences are cheaper than branches/jumping, aren't they?

   cmn
-- 
Carlos Martín Nieto    |   http://www.cmartin.tk
Hobbyist programmer    |


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