On Sun, May 13, 2012 at 10:40:41PM -0700, Yinghai Lu wrote: >On Sun, May 13, 2012 at 6:55 PM, Richard Yang ><weiyang@xxxxxxxxxxxxxxxxxx> wrote: >> On Mon, Apr 23, 2012 at 03:46:03PM -0400, Don Dutile wrote: >>>On 04/22/2012 11:52 AM, Richard Yang wrote: >>>>All, >>>> >>>>I am reading the pci_scan_bridge() and not sure what will happen in >>>>following situation. >>>> >>>>Suppose the kernel is not passed the pci=assign-busses. >>>> >>>>Below is a picture about the pci system. >>>> >>>> +-------+ >>>> | | root bridge(0,255) >>>> +---+---+ >>>> | Bus 0 >>>> -----+-----------+------------------------------+-- >>>> | | >>>> | | >>>> | | >>>> +----+----+ +-----+-----+ >>>> | | B1(1,15) | |B2(16,28) >>>> +----+----+ +-----+-----+ >>>> | Bus 1 | Bus 16 >>>> -----+----------------------- ----------+---------------- >>>> | >>>> +----+----+ >>>> | | B3 >>>> +---------+ >>>> >>>>Suppose B1 and B2 works fine with the BIOS, which get the right bus >>>>number and range. >>>> >>>>B3 does not works fine with the BIOS, which doesn't get the bus number. >>>> >>>>So in pci_scan_bridge(), B3 will be met in the second pass and get bus >>>>number 16? >>> >> Yinghai, >> >> Take my original question. >> >> B3 doesn't get the bus number, which its parent doesn't have free bus >> number and there is no gap between B1 and B2. >> >> So in this case, the probe_resource() can't find bus number for B3. >> Then cause pci_bridge_probe_busn_res() return non-zero. >> >> Then B3 couldn't work fine? > >B3 is on Bus 1? B3 is the one of bridges on Bus1? No, I omit other bridges on Bus#1. They will occupy bus number 2-15, which is calculated by BIOS and set to bridge's configuration space. > >if B3 is only bridge on Bus1, it probe_resource should return [2,15] >at first, and then scan B3. > >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
