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Subject[PATCH v4 20/27] Documentation: x86: convert i386/IO-APIC.txt to reST
This converts the plain text documentation to reStructuredText format and
add it to Sphinx TOC tree. No essential content change.

Signed-off-by: Changbin Du <>
Reviewed-by: Mauro Carvalho Chehab <>
.../x86/i386/{IO-APIC.txt => IO-APIC.rst} | 28 +++++++++++--------
Documentation/x86/i386/index.rst | 10 +++++++
Documentation/x86/index.rst | 1 +
3 files changed, 27 insertions(+), 12 deletions(-)
rename Documentation/x86/i386/{IO-APIC.txt => IO-APIC.rst} (93%)
create mode 100644 Documentation/x86/i386/index.rst

diff --git a/Documentation/x86/i386/IO-APIC.txt b/Documentation/x86/i386/IO-APIC.rst
similarity index 93%
rename from Documentation/x86/i386/IO-APIC.txt
rename to Documentation/x86/i386/IO-APIC.rst
index 15f5baf7e1b6..ce4d8df15e7c 100644
--- a/Documentation/x86/i386/IO-APIC.txt
+++ b/Documentation/x86/i386/IO-APIC.rst
@@ -1,3 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+:Author: Ingo Molnar <>
Most (all) Intel-MP compliant SMP boards have the so-called 'IO-APIC',
which is an enhanced interrupt controller. It enables us to route
hardware interrupts to multiple CPUs, or to CPU groups. Without an
@@ -13,9 +21,8 @@ usually worked around by the kernel. If your MP-compliant SMP board does
not boot Linux, then consult the linux-smp mailing list archives first.

If your box boots fine with enabled IO-APIC IRQs, then your
-/proc/interrupts will look like this one:
+/proc/interrupts will look like this one::

- ---------------------------->
hell:~> cat /proc/interrupts
0: 1360293 IO-APIC-edge timer
@@ -28,7 +35,6 @@ If your box boots fine with enabled IO-APIC IRQs, then your
NMI: 0
ERR: 0
- <----------------------------

Some interrupts are still listed as 'XT PIC', but this is not a problem;
none of those IRQ sources is performance-critical.
@@ -37,14 +43,14 @@ none of those IRQ sources is performance-critical.
In the unlikely case that your board does not create a working mp-table,
you can use the pirq= boot parameter to 'hand-construct' IRQ entries. This
is non-trivial though and cannot be automated. One sample /etc/lilo.conf


The actual numbers depend on your system, on your PCI cards and on their
PCI slot position. Usually PCI slots are 'daisy chained' before they are
connected to the PCI chipset IRQ routing facility (the incoming PIRQ1-4

,-. ,-. ,-. ,-. ,-.
PIRQ4 ----| |-. ,-| |-. ,-| |-. ,-| |--------| |
@@ -56,7 +62,7 @@ lines):
PIRQ1 ----| |- `----| |- `----| |- `----| |--------| |
`-' `-' `-' `-' `-'

-Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD:
+Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD::

INTD--| |
@@ -78,19 +84,19 @@ to have non shared interrupts). Slot5 should be used for videocards, they
do not use interrupts normally, thus they are not daisy chained either.

so if you have your SCSI card (IRQ11) in Slot1, Tulip card (IRQ9) in
-Slot2, then you'll have to specify this pirq= line:
+Slot2, then you'll have to specify this pirq= line::


the following script tries to figure out such a default pirq= line from
-your PCI configuration:
+your PCI configuration::

echo -n pirq=; echo `scanpci | grep T_L | cut -c56-` | sed 's/ /,/g'

note that this script won't work if you have skipped a few slots or if your
board does not do default daisy-chaining. (or the IO-APIC has the PIRQ pins
connected in some strange way). E.g. if in the above case you have your SCSI
-card (IRQ11) in Slot3, and have Slot1 empty:
+card (IRQ11) in Slot3, and have Slot1 empty::


@@ -105,7 +111,7 @@ won't function properly (e.g. if it's inserted as a module).
If you have 2 PCI buses, then you can use up to 8 pirq values, although such
boards tend to have a good configuration.

-Be prepared that it might happen that you need some strange pirq line:
+Be prepared that it might happen that you need some strange pirq line::


@@ -115,5 +121,3 @@ Good luck and mail to or if you have any problems that are not covered
by this document.

--- mingo
diff --git a/Documentation/x86/i386/index.rst b/Documentation/x86/i386/index.rst
new file mode 100644
index 000000000000..8747cf5bbd49
--- /dev/null
+++ b/Documentation/x86/i386/index.rst
@@ -0,0 +1,10 @@
+.. SPDX-License-Identifier: GPL-2.0
+i386 Support
+.. toctree::
+ :maxdepth: 2
diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
index 3eb0334ae2d4..4e15bcc6456c 100644
--- a/Documentation/x86/index.rst
+++ b/Documentation/x86/index.rst
@@ -26,3 +26,4 @@ x86-specific Documentation
+ i386/index
 \ /
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