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List: linux-hotplug
Subject: Re: Linux-hotplug-devel Digest, Vol 19, Issue 18
From: leilei175 () gmail ! com
Date: 2007-12-20 9:28:28
Message-ID: 82fc30000712200128p548a8521w6478ea12a09d2e84 () mail ! gmail ! com
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Thanks for your reply,I will ask redhat about this.
2007/12/20, linux-hotplug-devel-request@lists.sourceforge.net
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> 1. Re: a question on hardware probing mechanism in linux( before
> udev get run) (Greg KH)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 18 Dec 2007 15:09:52 -0800
> From: Greg KH <greg@kroah.com>
> Subject: Re: a question on hardware probing mechanism in linux( before
> udev get run)
> To: leilei175@gmail.com
> Cc: linux-hotplug-devel@lists.sourceforge.net
> Message-ID: <20071218230952.GB13614@kroah.com>
> Content-Type: text/plain; charset=us-ascii
>
> On Tue, Dec 18, 2007 at 02:25:01PM +0800, leilei175@gmail.com wrote:
> > I have checked many places to find the answer to this question.
> >
> > Apparently I'm not the only person bothered by this problem.
> > according to the explanation from redhat
> > ````````snip````````
> > The 2.6.9-55 version of the Red Hat Enterprise Linux 4 kernel (Update
> > 5) reverts to the 2.4 ordering of network interface cards (NICs) on
> > certain systems. Note that if the "HWADDR=MAC ADDRESS" line is present
> > in the /etc/sysconfig/network-scripts/ifcfg-ethX files, the NIC
> > ordering will not change.
> >
> > To restore the original 2.6 ordering, which is different from the 2.4
> > ordering, boot with the option pci=nobfsort
> > ``````````snip`````````
> >
> > I have checked the source code for this.Setting "pci=nobfsort" would
> > go to the pci_sort_breadthfirst kernel path.As I'm not quite familiar
> > with the pci subsystem of linux I can't figure out how the probing and
> > sorting process is going on.I guess there are a certain data structure
> > in the kernel space to store the hardware detecting result,and then
> > use the result along with modprobe.conf to insert the coresponding
> > module .After this the /sys fs can store information related to
> > hardware connected to this box.
> >
> > I am not sure if this is the right process of hardware probing and
> > device naming.
> >
> > Really apreciate your explaination to make this more clear to me.
> >
> > Thanks
> >
> > 2007/12/14, leilei175@gmail.com <leilei175@gmail.com>:
> > > Hi greg,
> > >
> > > I have some question about the naming method in linux.I have read a
> > > lot articles written by you concerning udev,all of them are quite
> > > useful,and the consistent naming rules is fantastic.However there is
> > > still some questions in my head.
> > > As udev is running in userspace,and it can't be used before /sysfs is
> > > mounted,how and when did linux kernel managed to probe all those
> > > devices connected to the box?I guess it has something to do with the
> > > init script file in initrd.img.
> > > such as:
> > > echo "Loading scsi_mod.ko module"
> > > insmod /lib/scsi_mod.ko
> > > echo "Loading sd_mod.ko module"
> > > insmod /lib/sd_mod.ko
> > > echo "Loading libata.ko module"
> > > insmod /lib/libata.ko
> > > echo "Loading ata_piix.ko module"
> > > insmod /lib/ata_piix.ko
> > > echo "Loading jbd.ko module"
> > > insmod /lib/jbd.ko
> > > echo "Loading ext3.ko module"
>
> What distro does this? That's pretty deterministic, no ordering issues
> there :)
>
> > > then another question comes to me,how did the kernel decide the order
> > > of these module inserting?Is this has anything to do with
> > > modprobe.conf file?
>
> It all depends on the distro involved.
>
> > > Actully this question come from a EL4U5 installation problem I am facing.
> > >
> > > when booting from "install CD".My two disks are detected as sda&sdb
> > > however after the installation(partition,format,installing packages)
> > > these two become sdb&sdc,the sda become my usb-storage.(no plug in or
> > > remove device during the installation)
> > >
> > > This problem never come up when installing other version of RedHat linux.
> > > In other version of EL and RHEL create /etc/modprobe.conf like this,
> > > @ alias scsi_hostadapter mptbase
> > > @ alias scsi_hostadapter1 mptsas
> > > @ alias scsi_hostadapter2 usb-storage
> > >
> > > But EL4 U5 creates,
> > > @ alias scsi_hostadapter usb-storage
> > > @ alias scsi_hostadapter1 mptbase
> > > @ alias scsi_hostadapter2 mptsas
> > > Because of this, "sda" is reserved for usb-storage and "mpt" devices shift.
> > > I'm not sure which command generates /etc/modprobe.conf file, and what
> > > determines the order of module inserting.
>
> As this is a RHEL specific question, I suggest you ask this on a RHEL
> mailing list, as I have no idea what they are doing in their init
> scripts, and it really has nothing to do with hotplug or udev issues at
> all, it looks to be all hard-coded here.
>
> good luck,
>
> greg k-h
>
>
>
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> End of Linux-hotplug-devel Digest, Vol 19, Issue 18
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