From 45db33709ccc7330c55fc6751c96468de407f2ac Mon Sep 17 00:00:00 2001 From: Logan Gunthorpe Date: Mon, 30 Jul 2018 10:18:38 -0600 Subject: PCI: Allow specifying devices using a base bus and path of devfns MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When specifying PCI devices on the kernel command line using a bus/device/function address, bus numbers can change when adding or replacing a device, changing motherboard firmware, or applying kernel parameters like "pci=assign-buses". When bus numbers change, it's likely the command line tweak will be applied to the wrong device. Therefore, it is useful to be able to specify devices with a base bus number and the path of devfns needed to get to it, similar to the "device scope" structure in the Intel VT-d spec, Section 8.3.1. Thus, we add an option to specify devices in the following format: [:]:.[/.]* The path can be any segment within the PCI hierarchy of any length and determined through the use of 'lspci -t'. When specified this way, it is less likely that a renumbered bus will result in a valid device specification and the tweak won't be applied to the wrong device. Signed-off-by: Logan Gunthorpe [bhelgaas: use "device" instead of "slot" in documentation since that's the usual language in the PCI specs] Signed-off-by: Bjorn Helgaas Reviewed-by: Stephen Bates Reviewed-by: Alex Williamson Acked-by: Christian König --- Documentation/admin-guide/kernel-parameters.txt | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index ab36fb34ed01..4fa4c9ff04ae 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3000,7 +3000,7 @@ or a set of devices (). These are specified in one of the following formats: - [:]:. + [:]:.[/.]* pci::[::] Note: the first format specifies a PCI @@ -3009,7 +3009,11 @@ firmware changes, or due to changes caused by other kernel parameters. If the domain is left unspecified, it is - taken to be zero. The second format + taken to be zero. Optionally, a path + to a device through multiple device/function + addresses can be specified after the base + address (this is more robust against + renumbering issues). The second format selects devices using IDs from the configuration space which may match multiple devices in the system. -- cgit v1.2.3