drm/i915: Only bind to function 0 of the PCI device

Early chipsets (gen2/3) used function 1 as a placeholder for multi-head.
We used to ignore these since they were not assigned to
PCI_CLASS_DISPLAY_VGA. However with 934f992c7 we attempt to bind to all
Intel PCI_CLASS_DISPLAY devices (and functions) to work in multi-gpu
systems. This fails hard on gen2/3.

Reported-by: Ferenc Wágner <wferi@niif.hu>
Tested-by: Ferenc Wágner <wferi@niif.hu>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=28012
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index e517447..cfb56d0 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -568,6 +568,14 @@ int i915_reset(struct drm_device *dev, u8 flags)
 static int __devinit
 i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
+       /* Only bind to function 0 of the device. Early generations
+        * used function 1 as a placeholder for multi-head. This causes
+        * us confusion instead, especially on the systems where both
+        * functions have the same PCI-ID!
+        */
+       if (PCI_FUNC(pdev->devfn))
+               return -ENODEV;
+
        return drm_get_pci_dev(pdev, ent, &driver);
 }