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SubjectRe: [PATCH] PNP: handle sysfs errors
On Wed, 11 Oct 2006 17:51:09 -0400
Jeff Garzik <jeff@garzik.org> 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.
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