On Thu, May 16, 2013 at 01:15:28PM +0200, Wolfram Sang wrote:

Lately, I have been experimenting how to improve the devm interface to make writing device drivers easier and less error prone while also getting rid of its subtle issues. I think it has more potential but still needs work and definately conistency, especiall in its usage.

The first thing I come up with is a low hanging fruit regarding devm_ioremap_resouce(). This function already checks if the passed resource is valid and gives an error message if not. So, we can remove similar checks from the drivers and get rid of a bit of code and a number of inconsistent error strings.

Sorry for jumping in so late. I generally like the idea. One small inconvenience is that devm_ioremap_resource() returns -EINVAL if res == NULL, which means that drivers will now also return -EINVAL in cases where no resource was returned. Typically drivers handle this by returning something like -ENODEV, -ENXIO, -ENOENT. Some do return -EINVAL but perhaps having a separate error code (and maybe error message as well) for a missing resource would be helpful.

Doing this would be rather easy now that you've paved the way by making devm_ioremap_resource() usage consistent across drivers.

Thierry