Messages in this thread | | | From | Bjorn Helgaas <> | Date | Thu, 11 Dec 2014 10:34:30 -0700 | Subject | Special handling of display/VGA devices in hotplug drivers |
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It looks like you added the initial pciehp driver [1], which includes the following code in pciehp_disable_slot():
+ if (class_code == PCI_BASE_CLASS_DISPLAY) { + /* Display/Video adapter (not supported) */ + rc = REMOVE_NOT_SUPPORTED;
+ /* If it's a bridge, check the VGA Enable bit */ + if ((header_type & 0x7F) == PCI_HEADER_TYPE_BRIDGE) { + rc = pci_bus_read_config_byte (pci_bus, devfn, PCI_BRIDGE_CONTROL, &BCR); + if (rc) + return rc; + + /* If the VGA Enable bit is set, remove isn't supported */ + if (BCR & PCI_BRIDGE_CTL_VGA) { + rc = REMOVE_NOT_SUPPORTED;
I'm trying to figure out why VGA devices are handled specially. I can't find anything in the PCI specs that mentions this. Most of the other PCI hotplug drivers have similar code. Do you remember anything about this?
Bjorn
[1] https://git.kernel.org/cgit/linux/kernel/git/tglx/history.git/commit/drivers/pci/hotplug/pciehp_ctrl.c?id=c16b4b14d9806e639f4afefa2d651a857a212afe
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