On Wed, Apr 27, 2011 at 1:38 AM, Ram Pai <linuxram@xxxxxxxxxx> wrote: > On Tue, Apr 26, 2011 at 05:25:00PM -0600, Bjorn Helgaas wrote: >> I'm uneasy about release_child_resources(). This patch doesn't add >> it, but it does add another use of it. >> >> What makes it safe for us to blindly release child resources? If we >> start with something like this: >> >> f2500000-f25fffff : PCI Bus 0000:0d >> f2500000-f25000ff : 0000:0d:00.0 >> f2500000-f25000ff : mmc0 >> >> and we call release_child_resources() on the top-level bridge window >> (f2500000-f25fffff), I think we will also release the 0000:0d:00.0 and >> mmc resources. This might not be a problem at boot-time, when the >> driver won't have claimed the device yet, but often we want to shuffle >> resources to make a hot-plugged device work, and then we do have to >> worry about other drivers. >> >> It seems like we need to check whether a driver is bound to a device, >> and if so, leave its resources alone. I didn't see anything like >> that, but maybe I missed it. > > But pci_assign_unassigned_resources() is called only during boot-time, > before any resources are assigned to any drivers. right? That's true today, but I expect it will be false soon. The problem of assigning resources and finding that we need to rearrange things is really the same, whether it occurs at boot-time or at hot-add time. I think we ought to use the same strategy either way. I think we're building on a faulty foundation, and I'd rather fix it now before we build more things on top of it. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
