Pretty much every feature that the blob provides. By turning down the above mentioned patch they essentially knocked out all the features of it as well. Don't forget that kernel guys also turfed out parts of the kernel in the past until they realized that virtualbox was also using them. Then all of a sudden they decided they would keep those in the kernel until vb had a chance to adjust.Do you have examples where they turned down patches that were needed to support features on anything other than its technical merits?
The greatest difficulty would more then likely having to interface with KMS (which as we know is a big no no because of the GPL licensing). You are also dealing with multiple memory manager between the two video devices.And I am not exactly clear on how GPL makes optimus impossible.
Are you seriously arguing that picking a default value is somehow equivalent to eliminating features? You do realize that people can still use Nvidia cards just fine even if they aren't the default, right?
Nvidia always waits until the last second on these things, and then it takes months or even years to get caught up, leaving users stranded in the meantime. It is exactly the philosophy you are espousing here that Nvidia needs to change. They do this every time, and every time it causes no end of problems to users.