On Wed, May 25, 2016 at 07:59:29PM +0000, Hefty, Sean wrote: > > It is time for the people who are hand waving about non-verbs, non-qp, > > 'new data transfers' to sit down and specify what they want to see out > > of the kernel uABI. > > I want the core ioctl framework to do this: > > 1. Map user objects to/from the kernel to validate pointers. > 2. Provide reference counting on such objects, in order to protect against the user attempting to destroy objects that are in use. > 3. Provide protection that the state of an object is not driven in two different directions. > 4. Safely process the removal of the underlying driver or device. > 5. Support driver specific operations to the kernel. > 6. Report events from multiple sources to a single file descriptor. > 7. Minimize the kernel footprint for allocated kernel objects. > 8. Minimize the code path needed to process any ioctl, without greatly affecting maintainability. > 9. Copy ioctl input/output data to/from the kernel. I agree with all of this as a suitable goal for the common dispatch/marshal framework. I like the idea of the generic uobject stuff in your patches. #6 seems 'not like the others' - seems like a reasonable concrete thing to consider as we build the objects on the framework. [understanding that compat operation is still required] > I started re-working my patch to address the rdma cm. The original > proposal wasn't generic enough and provided a poor fit, because the > rdma cm has a single object and 25 versions of 'modify'. I was imagining that all objects would be able to have a set of object specific functions beyond the common set. IIRC some verbs objects will need this as well, and I expect drivers to want it. This is why I wasn't thinking of using the ioctl # to dispatch the method. It is best if the driver specific calls have globally unique identifiers of some sort to protect against calling a method on the wrong driver. I would encourage you to go as far as Mellanox's series does and demonstrate the verbs context object in this framework ... Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
