From d96e1faccd0d9a074c70d690bd7fcb050c6c5e10 Mon Sep 17 00:00:00 2001 From: Martine Silbermann Date: Thu, 19 Feb 2004 17:20:38 -0800 Subject: [PATCH] [PATCH] PCI: update MSI Documentation After getting feedback from Tom,I made some changes to the patch Attached is a revised version. --- Documentation/MSI-HOWTO.txt | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/Documentation/MSI-HOWTO.txt b/Documentation/MSI-HOWTO.txt index 0dfcc5679b8aa..18526692de49c 100644 --- a/Documentation/MSI-HOWTO.txt +++ b/Documentation/MSI-HOWTO.txt @@ -1,6 +1,8 @@ The MSI Driver Guide HOWTO Tom L Nguyen tom.l.nguyen@intel.com 10/03/2003 + Revised Feb 12, 2004 by Martine Silbermann + email: Martine.Silbermann@hp.com 1. About this guide @@ -90,17 +92,14 @@ increase scalability. 5. Configuring a driver to use MSI/MSI-X By default, the kernel will not enable MSI/MSI-X on all devices that -support this capability once the patch is installed. A kernel -configuration option must be selected to enable MSI/MSI-X support. +support this capability. The CONFIG_PCI_USE_VECTOR kernel option +must be selected to enable MSI/MSI-X support. 5.1 Including MSI support into the kernel -To include MSI support into the kernel requires users to patch the -VECTOR-base patch first and then the MSI patch because the MSI -support needs VECTOR based scheme. Once these patches are installed, -setting CONFIG_PCI_USE_VECTOR enables the VECTOR based scheme and -the option for MSI-capable device drivers to selectively enable MSI -(using pci_enable_msi as desribed below). +To allow MSI-Capable device drivers to selectively enable MSI (using +pci_enable_msi as described below), the VECTOR based scheme needs to +be enabled by setting CONFIG_PCI_USE_VECTOR. Since the target of the inbound message is the local APIC, providing CONFIG_PCI_USE_VECTOR is dependent on whether CONFIG_X86_LOCAL_APIC @@ -130,7 +129,7 @@ PIN-IRQ assertion mode. 5.2 Configuring for MSI support Due to the non-contiguous fashion in vector assignment of the -existing Linux kernel, this patch does not support multiple +existing Linux kernel, this version does not support multiple messages regardless of the device function is capable of supporting more than one vector. The bus driver initializes only entry 0 of this capability if pci_enable_msi(...) is called successfully by @@ -232,7 +231,7 @@ however, in UP environment, users must manually set CONFIG_X86_LOCAL_APIC. Once CONFIG_X86_LOCAL_APIC=y, setting CONFIG_PCI_USE_VECTOR enables the VECTOR based scheme and the option for MSI-capable device drivers to selectively enable -MSI (using pci_enable_msi as desribed below). +MSI (using pci_enable_msi as described below). Note that CONFIG_X86_IO_APIC setting is irrelevant because MSI vector is allocated new during runtime and MSI support does not -- 2.53.0