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This is new just today. It's been working well for a while now.

When functioning normally, the driver will match on the USB device's product and vendor IDs, then will load and operate.

It's a USB video adapter so under normal operation, one sees a blurred image of the desktop until login, then you get a second screen that works correctly with Display Preferences.

But just today, if the dongle is attached at boot the driver doesn't load and the USB-attached monitor doesn't show an image.

If I unplug the dongle then plug it back in, it works.

If the dongle is not attached during boot, then plugged in after reaching the desktop, it works.

If the dongle is attached during boot, and I later use kextutil to load it, kextutil reports success but it doesn't load.

I speculate it is a problem with matching but don't understand what could have gone wrong.

It's a signed driver that's now in /Library/Extensions; previously it was unsigned, in /System/Library/Extensions, with System Integrity Protection disabled.

There are two other drivers in the product that are not USB function drivers. They load just fine. All three drivers work together to create a virtual frame buffer then display it.

pmdj
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Mike Crawford
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1 Answers1

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This could be caused by a bunch of different things. A few suggestions:

  1. Have you verified that ::probe() and ::start() are not being called on your driver class? If they return NULL/false, that will cause behaviour as described.
  2. What's the situation in the IORegistry when your driver has failed to load for a cold-plugged device? Does the nub you match have any client objects?
  3. Have you ruled out a kext cache problem? (E.g. are there any errors when the OS regenerates the kext cache and prelinked kernel?)

Posting your Info.plist might also help - it's possible the problem lies there.

pmdj
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