On Wednesday 11 October 2006 18:45, Andrew Morton wrote:
> On Wed, 11 Oct 2006 17:51:09 -0400
> Jeff Garzik <[email protected]> wrote:
>
> > + int rc = device_create_file(&dev->dev,&dev_attr_options);
> > + if (rc) goto err;
> > + rc = device_create_file(&dev->dev,&dev_attr_resources);
> > + if (rc) goto err_opt;
> > + rc = device_create_file(&dev->dev,&dev_attr_id);
> > + if (rc) goto err_res;
> > +
> > return 0;
> > +
> > +err_res:
> > + device_remove_file(&dev->dev,&dev_attr_resources);
> > +err_opt:
> > + device_remove_file(&dev->dev,&dev_attr_options);
> > +err:
> > + return rc;
>
> That's a common pattern, isn't it?
>
> I wonder if we could create some sort of automatic-unwinding engine:
>
> int pnp_interface_attach_device(struct pnp_dev *dev)
> {
> struct unwind_engine *u = NULL;
> int err;
>
> u = UNWINDABLE(u, err, device_create_file(&dev->dev,&dev_attr_options),
> device_remove_file, &dev->dev, &dev_attr_options);
> u = UNWINDABLE(u, err, device_create_file(&dev->dev,&dev_attr_id)
> device_remove_file, &dev->dev, &dev_attr_options);
> u = UNWINDABLE(u, err, device_create_file(&dev->dev,&dev_attr_id),
> device_remove_file, &dev->dev, &dev_attr_id);
> err = unwind(err, u);
> return err;
> }
>
> and, umm,
>
> #define UNWINDABLE(u, err, expr, undo_fn, arg1, arg2)
> if (err == 0) {
> err = (expr);
> if (err == 0)
> u = add_unwind(u, undo_fn, arg1, arg2);
> }
> u;
>
> int unwind(int err, struct unwind_engine *u)
> {
> if (err == 0)
> return 0;
> for (all entries in u in opposite order) {
> u->fn(u->arg0, u>arg1);
> kfree(u);
> }
> return err;
> }
>
>
> I dunno - probably too crappy to live, but it'd encourage/help people to
> dtrt.
The best solution is to switch drivers with more than 2 attributes
to use arribute groups which collapses unwinding nicely.
--
Dmitry
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