On Fri, Nov 11, 2022 at 10:48:16PM +0100, Pali Rohár wrote: > On Friday 11 November 2022 15:05:55 Bjorn Helgaas wrote: > > On Fri, Nov 11, 2022 at 09:09:45PM +0100, Pali Rohár wrote: > > > On Thursday 20 January 2022 15:02:12 Bjorn Helgaas wrote: > > > > On Thu, Jan 20, 2022 at 09:45:05PM +0100, Pali Rohár wrote: > > > > [trimmed material; beginning of thread is at > > https://lore.kernel.org/r/20211220155448.1233-3-pali@xxxxxxxxxx] > > > > > > > Meanwhile I found out that in linux/ioport.h file is IORESOURCE_WINDOW > > > > > constant with comment /* forwarded by bridge */ > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/ioport.h?h=v5.15#n56 > > > > > > > > > > But apparently it is not set for resources behind PCI bridges and > > > > > therefore it is not available in column of "resources" sysfs file. > > > > > > > > > > So maybe instead of adding new sysfs files, it would be better way to > > > > > implement this flag and export it in flags column of "resources" file > > > > > for every row which belongs to resources behind bridges? > > > > > > > > I looked at that, too. Today we only set IORESOURCE_WINDOW for host > > > > bridge windows. Maybe it could be set for PCI-to-PCI bridge windows, > > > > too. Would have to audit users to make sure it wouldn't break > > > > anything. > > > > > > Hello Bjorn, I would like to remind this older issue. Did you have a time > > > to audit usage of IORESOURCE_WINDOW? Some flag for resource forwarding > > > windows in PCI-to-PCI bridges would really help userspace application to > > > distinguish between IO/MEM BARs an IO/MEM forwarding windows. > > > > I had forgotten all about this issue. IIUC, the ultimate goal here > > is to help lspci distinguish between an I/O window that's disabled and > > one that's enabled at [io 0x0000-0x0fff]. > > > > I have not done the research to see whether it would be safe to set > > IORESOURCE_WINDOW for PCI-to-PCI bridge windows. I'm sorry if I left > > the impression that I intended to do that. I would welcome your help > > to do that. > > Ok, do you have some resources or other information at which I should > look? I just do not know where to start or what to check for that > research. > > I looked into kernel sources and the only places where is code checking > for IORESOURCE_WINDOW is ACPI related: arch/arm64/kernel/pci.c and > drivers/pnp/resource.c. And I do not fully understand how is ACPI > connected with PCI resources at this level. Other places which check > (lib/vsprintf.c and drivers/pnp/interface.c) just use it for > printf-formats. Yeah, that's the kind of thing I have in mind. I can't remember if I had any specific concern. Bjorn
