On Mon, Jun 4, 2012 at 6:34 AM, Richard Yang <weiyang@xxxxxxxxxxxxxxxxxx> wrote: > On Tue, May 29, 2012 at 10:14:51AM -0700, Yinghai Lu wrote: >>On Tue, May 29, 2012 at 4:59 AM, Richard Yang >><weiyang@xxxxxxxxxxxxxxxxxx> wrote: >>> >>> I think about this issue again, this behavior of kernel will bring some >>> unconvenience to the user. >>> >>> Do you think the kernel could handle this situation? >> >>in this extreme case, you may need user to do some comprise. >> >>We should always try to use setting from BIOS if it is sane. >> >>Yinghai > Yinghai > > +-------+ > | | root bridge(0,255) > +---+---+ > | Bus 0 > -----+-----------+------------------------------+-- > | | > | | > | | > +----+----+ +-----+-----+ > | | B1(1,15) | |B2(32,35) > +----+----+ +-----+-----+ > | Bus 1 | Bus 32 > -----+----------------------- ----------- > | > +----+----+ > | | B3 > +---------+ > > I reread the current code, v3.4, in linus tree, > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git > And I come up with another condition which will have a problem when > kernel is not given the parameter, pci=assign-busses. > > Same condition as previous: > ------------------------------------------------------------------------------- > B1 and B2 works fine with the BIOS and get the bus number assigned. > B3 is not probed by BIOS. > > Difference between the previous example: > ------------------------------------------------------------------------------- > In this case, B2 is assigned bus range (32, 35), which has a gap between > B1 number range (1, 15). > > When kernel meets B3 in second pass, B3 will be assigned with bus number > 16. Well, this time the bus number 16 doesn't overlap with bus number of > B2. > > But, the pci_fixup_parent_subordinate_busnr() will not work since the > pci=assign-buses is not passed to kernel. > > So B1's bus window is still (1,15) not (1,16). > > BTW, is this also a extrem case? that should be handled by busn_alloc branch. kernel will try to probe in [1,15] at first, and could extend B1 range to [1, 31] if needed. Thanks Yinghai -- 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
