On Wednesday 07 October 2020 12:47:40 Oliver O'Halloran wrote: > On Wed, Oct 7, 2020 at 10:26 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > > > I'm not really a fan of this because pci_sysfs_init() is a bit of a > > hack to begin with, and this makes it even more complicated. > > > > It's not obvious from the code why we need pci_sysfs_init(), but > > Yinghai hinted [1] that we need to create sysfs after assigning > > resources. I experimented by removing pci_sysfs_init() and skipping > > the ROM BAR sizing. In that case, we create sysfs files in > > pci_bus_add_device() and later assign space for the ROM BAR, so we > > fail to create the "rom" sysfs file. > > > > The current solution to that is to delay the sysfs files until > > pci_sysfs_init(), a late_initcall(), which runs after resource > > assignments. But I think it would be better if we could create the > > sysfs file when we assign the BAR. Then we could get rid of the > > late_initcall() and that implicit ordering requirement. > > You could probably fix that by using an attribute_group to control > whether the attribute shows up in sysfs or not. The .is_visible() for > the group can look at the current state of the device and hide the rom > attribute if the BAR isn't assigned or doesn't exist. That way we > don't need to care when the actual assignment occurs. And cannot we just return e.g. -ENODATA (or other error code) for those problematic sysfs nodes until late_initcall() is called? > > But I haven't tried to code it up, so it's probably more complicated > > than this. I guess ideally we would assign all the resources before > > pci_bus_add_device(). If we could do that, we could just remove > > pci_sysfs_init() and everything would just work, but I think that's a > > HUGE can of worms. > > I was under the impression the whole point of pci_bus_add_device() was > to handle any initialisation that needed to be done after resources > were assigned. Is the ROM BAR being potentially unassigned an x86ism > or is there some bigger point I'm missing? > > Oliver
