On Wed, Mar 30, 2016 at 11:51:50AM -0400, Rob Groner wrote: > On Tue, 2016-03-29 at 17:57 -0700, Greg KH wrote: > > On Tue, Mar 29, 2016 at 04:11:22PM -0400, Rob Groner wrote: > > > Your first glance is probably correct. The driver handles reads and > > > writes to registers via IOCTLs from the user library, as well as > > > interrupts and DMA. There are probably two main reasons the driver is > > > structured like that: 1) All "new" drivers here are essentially tailored > > > versions of previous drivers that have been around for a while, so this > > > wasn't built-from-scratch new. While it means that any poor design > > > decisions made early on are perpetuated, it also means to us that we > > > aren't re-inventing the wheel and we're mostly using a driver that has > > > proven to work for quite a while. 2) The library code for the board is > > > shared (internally) with our Windows driver package, and in some cases > > > DOS too. Since Windows uses IOCTLs, we can essentially share the exact > > > same library files, and only the IOCTL call itself is OS-specific. > > > > > > I know #1 is not a good reason and I'd be happy to work towards > > > re-writing the driver in a more correct way, but probably not if it > > > would cause us to have to split into a Linux and Windows library > > > versions. Keeping the library common at this point has saved us a lot > > > of development time. > > > > I understand the need for userspace libraries to be "unified", but you > > might be able to get away with no kernel driver at all, just use the UIO > > driver for your device and then read/write the memory mapped area of > > your card directly from your library/application. That will have the > > benifit of making your Linux implementation faster as well :) > > I'm looking at the UIO API for the first time, and I'm beginning to > understand it, and I *do* see the benefits of it. Instead of working to > get this driver accepted in the kernel, I think I am going to instead > make a UIO implementation my pet project. > > From what I've learned so far, I'll still need a kernel driver for the > interrupt handler, just much smaller. That is correct. > One thing I haven't been able to > find out for sure, however, is if DMA is possible through a UIO > implementation. Not seeing any mention of it on kernel.org isn't > encouraging. It keeps coming up in dicussion on how to do this in a "generic" way, look at the lkml archives for the details. But you can do this in a specific-way for your own device, there are 2 drivers in the tree that handle this in some manner, try looking at those for inspiration. thanks, greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
