On Fri, Dec 17, 2021 at 11:29:28AM -0600, Bjorn Helgaas wrote:
> Hi Ville,
> 
> Thanks for the report!
> 
> On Fri, Dec 17, 2021 at 12:44:51PM +0200, Ville Syrjälä wrote:
> > Hi,
> > 
> > The pci sysfs "rom" file has disappeared for VGA devices.
> > Looks to be a regression from commit 527139d738d7 ("PCI/sysfs:
> > Convert "rom" to static attribute").
> > 
> > Some kind of ordering issue between the sysfs file creation 
> > vs. pci_fixup_video() perhaps?
> 
> Can you attach your complete "lspci -vv" output?  Also, which is the
> default device?  I think there's a "boot_vga" sysfs file that shows
> this.  "find /sys -name boot_vga | xargs grep ."

All I have is Intel iGPUs so it's always 00:02.0. 

$ cat /sys/bus/pci/devices/0000\:00\:02.0/boot_vga 
1
$ cat /sys/bus/pci/devices/0000\:00\:02.0/rom
cat: '/sys/bus/pci/devices/0000:00:02.0/rom': No such file or directory

I've attached the full lspci from my IVB laptop, but the problem
happens on every machine (with an iGPU at least).

I presume with a discrete GPU it might not happen since they
actually have a real ROM.

> 
> I think the relevant path is something like this:
> 
>   acpi_pci_root_add
>     pci_acpi_scan_root
>       ...
>         pci_scan_single_device
>           pci_device_add
>             device_add
>               ...
>                 sysfs_create_groups
>                   ...
>                     if (grp->is_visible())
>                       pci_dev_rom_attr_is_visible  # after 527139d738d7
>                         if (pci_resource_len(pdev, PCI_ROM_RESOURCE))
>                           ...
>     pci_bus_add_devices
>       pci_bus_add_device
>         pci_fixup_device(pci_fixup_final)
>           pci_fixup_video
>             if (vga_default_device() ...)
>               # update PCI_ROM_RESOURCE
>         pci_create_sysfs_dev_files
>           if (pci_resource_len(pdev, PCI_ROM_RESOURCE))
>             sysfs_create_bin_file("rom")           # before 527139d738d7
> 
> Prior to 527139d738d7, we ran pci_fixup_video() in
> pci_bus_add_devices().  The vga_default_device() there might depend on
> the fact that we've discovered all the PCI devices.  
> 
> After 527139d738d7, we create the "rom" file in pci_device_add(),
> which happens as we discover each device, so maybe we don't yet know
> which device is the default VGA device.
> 
> Bjorn

-- 
Ville Syrjälä
Intel