Re: [PATCH] agp/amd64: Bind to unsupported devices only if AGP is present

[Lukas Wunner <lukas@wunner.de>]

On Wed, Jun 25, 2025 at 08:43:45PM +0200, Hans de Goede wrote:
> On 25-Jun-25 4:33 PM, Lukas Wunner wrote:
> > So how do you know that all of these unsupported devices have
> > PCI_CLASS_BRIDGE_HOST?
> 
> The top of the driver says
> 
>  * This is a GART driver for the AMD Opteron/Athlon64 on-CPU northbridge.
>  * It also includes support for the AMD 8151 AGP bridge
> 
> Note this only talks about north bridges.
> 
> Also given the age of AGP, I would expect the agp_amd64_pci_table[]
> to be pretty much complete and the need for probing for unknown AGP
> capable bridges is likely a relic which can be disabled by default.
> 
> Actually the amd64-agp code is weird in that has support for
> unknown AGP bridges enabled by default in the first place.

I agree that probing *any* PCI device should never have been introduced,
much less made the default.  But changing that risks regressing
users that depend on it.

The conservative approach is to retain the existing behavior,
but make it more benign by constraining probing to devices with
AGP Capability, as we did prior to 6fd024893911.

Thanks,

Lukas