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PCI: Add pci_is_vga() helper

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The PCI Code and ID Assignment spec, r1.15, secs 1.4 and 1.1, define
VGA Base Class and Sub-Classes:

  03 00  PCI_CLASS_DISPLAY_VGA      VGA-compatible or 8514-compatible
  00 01  PCI_CLASS_NOT_DEFINED_VGA  VGA-compatible (before Class Code)

Add a pci_is_vga() helper to return true if a device is in either category.

These VGA devices use the hardwired legacy VGA resources
([mem 0xa0000-0xbffff], [io 0x3b0-0x3bb], [io 0x3c0-0x3df] and aliases), so
they require special handling if more than one is present in the system.

Link: https://lore.kernel.org/r/20230830111532.444535-2-sui.jingfeng@linux.dev
Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
[bhelgaas: commit log, drop !pdev test]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: "Maciej W. Rozycki" <macro@orcam.me.uk>
This commit is contained in:
Sui Jingfeng 2023-08-30 19:15:28 +08:00 committed by Bjorn Helgaas
parent 0bb80ecc33
commit 7e845ecb2f
1 changed files with 24 additions and 0 deletions
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24
include/linux/pci.h
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@ -713,6 +713,30 @@ static inline bool pci_is_bridge(struct pci_dev *dev)
dev->hdr_type == PCI_HEADER_TYPE_CARDBUS;
}
/**
* pci_is_vga - check if the PCI device is a VGA device
*
* The PCI Code and ID Assignment spec, r1.15, secs 1.4 and 1.1, define
* VGA Base Class and Sub-Classes:
*
* 03 00 PCI_CLASS_DISPLAY_VGA VGA-compatible or 8514-compatible
* 00 01 PCI_CLASS_NOT_DEFINED_VGA VGA-compatible (before Class Code)
*
* Return true if the PCI device is a VGA device and uses the legacy VGA
* resources ([mem 0xa0000-0xbffff], [io 0x3b0-0x3bb], [io 0x3c0-0x3df] and
* aliases).
*/
static inline bool pci_is_vga(struct pci_dev *pdev)
{
if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
return true;
if ((pdev->class >> 8) == PCI_CLASS_NOT_DEFINED_VGA)
return true;
return false;
}
#define for_each_pci_bridge(dev, bus) \
list_for_each_entry(dev, &bus->devices, bus_list) \
if (!pci_is_bridge(dev)) {} else