On Tue, Oct 03, 2023 at 11:30:54AM -0500, Mario Limonciello wrote: > On 10/3/2023 04:44, Mika Westerberg wrote: > > On Mon, Oct 02, 2023 at 01:10:25PM -0500, Mario Limonciello wrote: > > > Before d3cold was stable userspace was allowed to influence the kernel's > > > decision of whether to enable d3cold for a device by a sysfs file > > > `d3cold_allowed`. This potentially allows userspace to break the suspend > > > for the system. > > > > > > For debugging purposes `pci_port_pm=` can be used to control whether > > > a PCI port will go into D3cold and runtime PM can be turned off by > > > sysfs on PCI end points. > > > > > > Change the sysfs attribute to read-only and simplify the internal kernel > > > logic to avoid needing to store the userspace request. > > > > I wonder if this ends up breaking some userspace apps? Not objecting > > though, just wanted to mention ;-) > > > > One thing we could do is to taint the kernel or log a warning if > > userspace touches this but allow it to do so. > > If we collectively decide it needs to stay RW for userspace compatbility > then I'll respin it to keep the store call but ignore whatever is written, > return -EINVAL and emit a pr_warn_once() that it's a no-op. I'd suggest to return 0 to avoid even the faintest ABI change whiff. Just emit a warning once explaining that the feature is deprecated and mark the attribute as such in ABI documentation. Thanks, Lukas
