From 92ed9865212bfad48e40f789e36845f69b4580f8 Mon Sep 17 00:00:00 2001 From: Marek Vasut Date: Wed, 10 Oct 2018 21:27:07 +0200 Subject: [PATCH] pci: Update documentation to make 'compatible' string optional Reword the documentation to make it clear the compatible string is now optional, yet still matching on it takes precedence over PCI IDs and PCI classes. Signed-off-by: Marek Vasut Cc: Simon Glass Cc: Tom Rini Reviewed-by: Bin Meng --- doc/driver-model/pci-info.txt | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/doc/driver-model/pci-info.txt b/doc/driver-model/pci-info.txt index e1701d1..14364c5 100644 --- a/doc/driver-model/pci-info.txt +++ b/doc/driver-model/pci-info.txt @@ -34,11 +34,15 @@ under that bus. Note that this is all done on a lazy basis, as needed, so until something is touched on PCI (eg: a call to pci_find_devices()) it will not be probed. -PCI devices can appear in the flattened device tree. If they do this serves to -specify the driver to use for the device. In this case they will be bound at -first. Each PCI device node must have a compatible string list as well as a - property, as defined by the IEEE Std 1275-1994 PCI bus binding document -v2.1. Note we must describe PCI devices with the same bus hierarchy as the +PCI devices can appear in the flattened device tree. If they do, their node +often contains extra information which cannot be derived from the PCI IDs or +PCI class of the device. Each PCI device node must have a property, as +defined by the IEEE Std 1275-1994 PCI bus binding document v2.1. Compatible +string list is optional and generally not needed, since PCI is discoverable +bus, albeit there are justified exceptions. If the compatible string is +present, matching on it takes precedence over PCI IDs and PCI classes. + +Note we must describe PCI devices with the same bus hierarchy as the hardware, otherwise driver model cannot detect the correct parent/children relationship during PCI bus enumeration thus PCI devices won't be bound to their drivers accordingly. A working example like below: