View source for Lt hotswap

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=== lt_hotswap ===
The <tt>lt_hotswap</tt> kernel module enables hot-swapping of UltraBay disk drives under Linux, with DMA support.
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===Features===
*enable hotswapping of [[UltraBay]] drives
*automatic IDE unregistering on [[ibm-acpi]] eject event
*leaves DMA support intact

===Limitations===
* Requires [[ibm-acpi]] to be running (does not work with [[APM]]).
* Works only in conjunction with the <tt>ide-disk</tt> driver (recent ThinkPad models use <tt>ata_piix</tt> instead). 
* Does '''not''' get on well with idectl. Use one, or the other, or crash.

===Project Homepage / Availability===
*Project page: http://www.sourceforge.net/projects/lths
*Latest version: http://prdownloads.sourceforge.net/lths/lt_hotswap-0.3.6.tar.gz?download

Development and discussion of lt_hotswap is currently being held in 
[[Mailinglists#Linux-ThinkPad Mailinglist|Linux-ThinkPad Mailinglist]].

===Installation===
In order to use the driver you must use ACPI and also have the [[ibm-acpi]] driver linked to your kernel (module or compiled).  

When loading the hotswap module, you can use the module parameter: {{bootparm|auto_eject|1}} to automatically unregister the drives IDE interface.  This will happen upon popping out the [[UltraBay]] lever.

===Supported models===
The driver has been explicitly reported to work on the following models. It should work on many others as well:
*ThinkPad {{A31p}} (warmswap), {{X22}}, {{T30}}, {{T22}}, {{T23}}, {{T40}}, {{T42}}

<tt>lt_hotswap</tt> does '''not''' work well on models that require  the <tt>ata_piix</tt> driver rather than the generic <tt>ide-disk</tt> IDE driver. See [[problems with SATA and Linux]] for a list, and [[How to hotswap UltraBay devices]] for an alternative solution on these models.

At least for a thinkpad T41p with a 2.6.15 kernel I recommend to use version 0.2 of lt_hotswap - the latest version reproducable produces oopses and kernel crashes for me.

===Script to eject an optical ultrabay drive===
I configured my system to automatically eject my optical drive in battery mode, because it saves about 500mW which is about 5% when my system is idle.
But when the drive is in use, issuing an eject will result in a kernel ooops/crash.
So the problem is: How do I check if the device is still in use, either by the kernel or by some other process? 
The trick is to compile "cdrom and ide_cd" as modules. If the unload of ide_cd failes some other process is still using the device.

 #!/bin/sh
 # disable bay if possible
 # saves about 500mW
 
 if modprobe -r ide_cd; then
   modprobe -r cdrom
   echo "MSTR eject" > /proc/acpi/lths
   modprobe ide-cd
   modprobe cdrom
 else
   echo ""
   echo "$(fuser -vm /dev/hdc)"
 fi


[[Category:Drivers]] [[Category:Patches]]

==See also==
* [[How to hotswap UltraBay devices]]
* [[How_to_hotswap_the_UltraBase]]