Re: [Qemu-devel] [PATCH v2 1/2] memory: Fix old portio word accesses

[Avi Kivity <avi@redhat.com>]

On 09/19/2011 04:55 PM, Gerd Hoffmann wrote:
>
> If the register access is trivial then you don't need to call into the 
> driver at all ...
>
> You can have a look at hw/intel-hda.c which actually implements 
> something like this, with some commonly needed features:
>
>   * The "offset" field already mentioned by avi is there, so trivial
>     reads/writes can be handled by the core.
>   * A "wmask" field to specify which bits are guest writable.
>   * A "wclear" field to specify which bits have write-one-to-clear
>     semantics.
>   * A "reset" field which specified the value this field has after
>     device reset.  Also serves as value for read-only registers.
>   * read/write handlers of course.  The write handler is called after
>     the core applied sanity checks and calculated the new register
>     value (using wmask+wclear).
>   * A "name" field (for debug logging).
>
> It's pretty nice, alot more readable that a big switch, forces you to 
> think which bits the guest can set (not specifying a wmask gives you a 
> read-only register ;).
>
> Also no bloat.  With this moving to memory core the all the handlers 
> will gain a line with a container_of(), but that isn't too bad too IMHO.

It's also more secure.  Move as much as possible into the core, and 
review (and fuzz) that like hell.

-- 
error compiling committee.c: too many arguments to function