On Mon, Jun 04, 2012 at 04:36:33PM -0700, Yinghai Lu wrote: >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. Hmm... when do you think this branch will be merged to the mainstream? > >Thanks > >Yinghai -- Richard Yang Help you, Help me -- 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
