Re: [Cocci] changing of_get_mac_address() to pass a buffer

[Julia Lawall <julia.lawall@inria.fr>]

On Mon, 5 Apr 2021, Michael Walle wrote:

> Hi Mansour,
>
> Am 2021-04-04 19:48, schrieb Mansour Moufid:
> > On Thu, Apr 1, 2021 at 4:13 AM Michael Walle <michael@walle.cc> wrote:
> > >
> > > Hi,
> > >
> > > so first I need to say I've never used coccinelle before,
> > > so please bear with me ;)
> > >
> > > To make of_get_mac_address() work with DSA ports (and a nvmem
> > > provider) I'd need to change the semantics of of_get_mac_address().
> > > Right now it returns a pointer to "const char *", I'd need to change
> > > that so a buffer will be passed as a parameter in which the MAC
> > > address gets stored.
> > >
> > > (1) Usually the call is something like:
> > >
> > >    const char *mac;
> > >    mac = of_get_mac_address(np);
> > >    if (!IS_ERR(mac))
> > >      ether_addr_copy(ndev->dev_addr, mac);
> > >
> > > This would need to be changed to:
> > >
> > >    of_get_mac_address(np, ndev->dev_addr);
> >
> > Here is one possible approach, doing the API change first then
> > handling the conditionals. It seems to work.
> >
> > @a@
> > identifier x;
> > expression y, z;
> > @@
> > -   x = of_get_mac_address(y);
> > +   x = of_get_mac_address(y, z);
> >     <...
> > -   ether_addr_copy(z, x);
> >     ...>
> >
> > @@
> > identifier a.x;
> > @@
> > -   if (<+... x ...+>) {}
> >
> > @@
> > identifier a.x;
> > @@
> >     if (<+... x ...+>) {
> >         ...
> >     }
> > -   else {}
> >
> > @@
> > identifier a.x;
> > expression e;
> > @@
> > -   if (<+... x ...+>@e)
> > -       {}
> > -   else
> > +   if (!(e))

Maybe try the above line without the parentheses around e?


> >         {...}
> >
> > @@
> > expression x, y, z;
> > @@
> > -   x = of_get_mac_address(y, z);
> > +   of_get_mac_address(y, z);
> >     ... when != x
>
> Thanks a lot!
>
> See also
> https://lore.kernel.org/netdev/20210405164643.21130-1-michael@walle.cc/
>
> There were some "if (!(!IS_ERR(x))", which I needed to simplify
> manually. Didn't noticed that in my previous script. I'm just
> curious, is that also something coccinelle can simplify on its
> own?

You can certainly write another rule for it:

- !(!e)
+ e

julia


>
> -michael
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