hi ya'll. i was going through some kernel options today and i saw a description of hotplug support which directed me to this site - http://linux-hotplug.sourceforge.net/?selected=about

my question is this. do you think this is a solution which would let me swap modular bay devices on the fly a'la softex's bay manager in windows? in windows, if my modular bay dvd is in, i can use the bay manager to coordinate swapping that device with let's say my modular bay floppy or modular bay zip drive. does this do the same thing? if it does, anyone have any experience setting this up and what do i need to download and install? there's a lot of different packages at that site. thanks.

Yes and no... hrmm... If I remember right, Linux will still go ape-poo if an IDE device is detached on the fly, so you might try your hand at it emulating the cdrom to scsi, or really, if the cdrom and zip drives both get emulated to scsi anyway... heck, Can you post back with a "dmesg" or two depending on which you have attached. If they can all be emulated to scsi, then maybe its possible as scsi can handle a hotswapped drive. Then again, if power needs to be cut to the device to detach it, probably not... fun to find out regardless.

Cheers,

Finegan

hey finegan. thanks for replying. i had first hand experience with linux going ape-poo when i tried as an experiment to manually hotswap my dvd drive with my floppy drive.... lol....

but anyway, here's a dmesg output. don't know if it's the one you're looking for though.

anyway my modular bay dvd is hdc (the modular zip would be hdc also while the modular floppy would be fd0). it looks like my internal cdrw is using scsi/scsi emulation. i don't think the modular bay dvd is though. it looks like hotplug may work though if i made all the modular bay devices emulate scsi though, if i didn't misread the hotplug site. lemme know what you think. thanks again.

edit: odd, it says dma disabled for hdb and hdc while the output of hdparm -v /dev/hdX shows dma enabled for both of them...

edit #2: oh yeah, i haven't been using my zip drive because it has the same label as (hdc) as my dvd rom which causes fstab to give a wrong fs, multiple fs error. anyway i tried changing fstab with the zip booted up and making a zip entry with the dvd rom entry commented out. i used the fs of vfat. same error. can anybody tell what the fs for a zip drive is?


edit #3: nevermind on the zip thing. i got it working. had to put in the grub.conf the boot option of hdc=ide-scsi and kudzu picked it up. i did have to change the fstab settings and links on my dvd though since the device is now /dev/scd1 instead of /dev/hdc which was what it was before.

Yeah, emulate everything /dev/hdc to scsi, heck... try and see if it'll take fd0 to scsi!

DMA is disabled for boot in specifically your motherboard, its re-enabled when apm kicks in. Its a kernel top level work around for just that laptop, neat huh? Only some Toshibas have that distinction too.

Its not really a matter of hotplugging, since the idea is to emulate everything to scsi that could be put in and out of that modular bay. IDE support in the kernel doesn't have the ability to rescan the bus on the fly, but scsi of course does, since there are hotswapable drives. This is a bit of an experiment as I have no idea where to even look up whether an emulated scsi device will scan properly under these conditions, but if you're willing to try!

Also, I would leave out any entries for the hotswap devices in fstab, and also make certain they are unmounted when you try a switch. Just to make certain the kernel doesn't try and do anything funny with them becuase mountd told it to.

Cheers,

Finegan

well, i just did an experment where i pulled out the dvd rom and replaced it with the zip drive without doing any prepping and linux didn't go ape-poo.

anyway, i'm guessing i need to do a few things before and after hotswapping to get it to really work.

i'm guessing, i need to ensure that the device isn't mounted, unload the device, maybe unregister (?) the device, replace the device with the desired device, load the new device, maybe register (?) the new device, and then mount and use.

what services/processes/programs do i need to use to handle unloading/loading and (?) registering/unregistering (?) the device and making the correct changes to the necessary files?

Its not really a matter of registering and unregistering the device, all that stuff from the hotplugging page really doesn't apply, you could have done this with a 2.2 kernel. Its, how is the kernel handling all of this device pulling, what did "dmesg" register after you hot swapped the drive? I'm thinking it just dealt with the device being yanked and that was no big deal. Dell is no slouch, they probably would have made sure the device itself would be okay and not rely on software to pull it... at least I hope. From the kernel's point of view, you just hotswapped a scsi drive, it just happened to be a DVD-rom on a laptop instead of a 32Gb Seagate on an Adaptec card. At least I think, was the new device available?

Cheers,

Finegan

well, i didn't do dmesg after "hotswapping" the dvd drive with the zip drive. but trying to mount the zip drive yielded an error of sda4 is not a valid block device. so the kernel (or internally) didn't register the swap or rescan the bus. also clicking the dvd drive icon did cause the zip drive to start whirring and popped up the error message of wrong fs type which makes sense since the dvd rom fs in fstab is iso9660 while the zip is set to auto.

hee hee....

You gotta comment that info out of fstab, either that's the problem, or the command that that button runs is:

mount -t iso9660 /dev/scd0 /mnt/cdrom

When you want:

mount -t vfat /dev/scd0 /mnt/cdrom

I think the kernel didn't rescan the bus, so the new device has the old device's name. This isn't bad, its just going to make all of your scripts not really work... you could edit the button's properties so that it takes out the file type:

mount /dev/scd0 /mnt/hotswap

And then of course create a directory called hotswap. Without a filesystem type declard, mount will just guess, and it almost always guesses correctly... offhand the only time I've had to tell it was an hfs+ burnt DVD.

Cheers,

Finegan

makes sense and it sounds like it would work, but i think i'm stopping this little experiment. my dvd drive doesn't sound normal anymore. instead of whirring up "constantly", it now whirs up and then has 2 or 3 "hiccups" which sound almost like grinding, although dvds and cds play with no problems. It just sounds different and almost sickly to me.

after perusing the net, it seems there's a common consensus that ide, atapi, and scsi aren't really made for just being swapped out without some kind of preperation and doing so is a dangerous proposition.