On Tue, Apr 05, 2016 at 08:55:54AM -0700, John Baldwin wrote: > Mostly I do not have experience with MGTDEVICE, though I was planning to > look at it as a way to implement this. Two things though: 1) there may > not be a cdev to associate with, and 2) I know of at least one device driver > that would use this in addition to using this for a general "map this BAR" > ioctl on /dev/pci. So /dev/pci is the natural cdev to place the functionality. An ioctl on /dev/pci may mmap BAR and return the base address.
> There are other cases in the past where I used OBJT_SG > but would have preferred to use a variant that used managed pages so that > I could invidate any existing mappings. In particular what I want to do > is invalidate an object so that any future uses fail. > > Alternatively, it might be nice to hook a destructor call into a VM object > so that I could know when the object is no longer in use (knowing that all > its mappings have been destroyed). When using OBJT_SG objects as aliases > for other things (memory allocated via contigmalloc or bus_dma or for > resources like PCI BARs), I could keep a reference count on the original > "thing" that I increment when creating an OBJT_SG object to return from > something like d_mmap_single() or the /dev/pci ioctl and drop the reference > count in the destructor hook for that object. This is in essence how GEM objects + MGTDEVICE mappings work for i915. The only bottleneck in the API arrangement is that d_mmap_single() only gets the offset as the identifying data to construct the mapping. For /dev/pci, the offset parameter would need to encode d:b:s:f and BAR index. _______________________________________________ email@example.com mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"