http://elinux.org/index.php?title=IDE_No_Probe_Specification&feed=atom&action=historyIDE No Probe Specification - Revision history2013-06-18T22:25:51ZRevision history for this page on the wikiMediaWiki 1.22alphahttp://elinux.org/index.php?title=IDE_No_Probe_Specification&diff=20969&oldid=prevPeter Huewe: /* Remaining Issues */2010-05-14T04:03:48Z<p><span dir="auto"><span class="autocomment">Remaining Issues</span></span></p>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>  - see if "noprobe" behavior has changed in 2.6</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>  - see if "noprobe" behavior has changed in 2.6</div></td></tr>
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</table>Peter Huewehttp://elinux.org/index.php?title=IDE_No_Probe_Specification&diff=1992&oldid=prevRBot: Bot (Edward's framework)2007-03-06T03:33:31Z<p>Bot (Edward's framework)</p>
<p><b>New page</b></p><div><br />
<pre>#noprint<br />
VERSION 0.3 - for other versions, click the "info" button.<br />
<br />
'''Table Of Contents:'''<br />
[[TableOfContents]]<br />
#noprint</pre><br />
<br />
<br />
== Introduction ==<br />
<br />
This is the specification for a change in behavior of Linux support for the IDE "noprobe" option.<br />
<br />
Historically, the IDE driver supports command line options to avoid probing certain devices and interfaces. <br />
/\ ''Note - The command line options for the IDE driver are documented in the<br />
file <code>drivers/ide/ide.c</code>, in a comment right before the routine ide_setup()<br />
(at about line 3200 in the file).''<br />
<br />
The "ide<x>=noprobe" option was found not to work as expected in the in the 2.4.20 code.<br />
<br />
The basic problem is that the data structures that describe possible IDE interfaces are<br />
initialized to indicate "noprobe" when the option is set at the kernel command line.<br />
However, later some drivers reset the value of "noprobe" in the data structures<br />
when certain interfaces are detected.<br />
<br />
The end result is that (at least in Linux version 2.4.20) the kernel command line<br />
processing for "ide<x>=noprobe" has no practical effect.<br />
<br />
The desired behavior is that the "noprobe" option will be observed, even if <br />
subsequent driver initialization finds out that an interface is actually present.<br />
<br />
== Rationale ==<br />
Todd Poynor of [[Monta Vista]] measured the effect of specifying "hdf=none ide3=noprobe" (avoid probing ide2 slave and both ide3 devices) on a 200MHz IBM 405GP "Walnut" evaluation board with a 33MHz PCI bus. A Seagate Barracuda ATA IV 60GB disk drive was cabled to one of the two IDE interfaces on a Promise Ultra66 PCI-IDE bridge card (PDC20262 chipset). All of the drivers for PCI, IDE, PCI-IDE disk, and EXT2 file system were built into the kernel. <br />
<br />
The time to initialize IDE was 1.3 seconds when the missing devices were probed, and about 230 milliseconds when "hdf=none ide3=noprobe" was specified. Thus the resulting bootup time savings, with<br />
"noprobe" properly observed by the Linux kernel, were about 1.1 seconds, in this test. <br />
<br />
This specification is needed because the kernel sometimes fails to observe the "noprobe"<br />
command line option.<br />
<br />
== Specifications ==<br />
# When the "ide<x>=noprobe" option is specified on the kernel command line, the IDE driver in the Linux kernel SHALL avoid probing the specified IDE interface. 2. When the "hd<x>=noprobe" option is specified on the kernel command line, the IDE driver in the Linux kernel SHALL avoid probing the specified IDE device.<br />
<br />
== Notes (informational and non-normative) ==<br />
# Processing for the option "hd<x>=none" (which is related to the "hd<x>=noprobe" option) is specific to a single processor architecture (i386). No aspect of the behavior of this option is specified here.<br />
<br />
== References ==<br />
See the page [http://tree.celinuxforum.org/pubwiki/moin.cgi/IDENoProbe IDENoProbe] for more<br />
information about this problem, and for a sample implementation.<br />
<br />
== Remaining Issues ==<br />
- see if "noprobe" behavior has changed in 2.6</div>RBot