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What happens when KMS fails?

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closed as not a real question by Tom Brossman, Uri Herrera, Mitch, Takkat, stephenmyall Sep 14 '12 at 14:28

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

You might want to add some more information to the question (and streamline the subject and question itself). Now you have 2 distinct questions and neither provide information on what you really want to know. – Ressu Aug 5 '10 at 13:57
up vote 3 down vote accepted

Mode setting is basically setting up the screen resolution and the depth mode for the graphics card.

From Wikipedia:

Mode-setting can be done in kernel space or in user space. Doing mode-setting in kernel-space is more flexible. Doing kernel-based mode-setting allows displaying an error in the case of a fatal error in the kernel, even when using a user-space display server. User-space mode-setting would have needed superuser privileges for direct hardware access. So kernel-based mode-setting increases security because the user-space graphics server does not need superuser privileges.

From Ubuntu Wiki on Kernel Mode Setting:

Kernel mode-setting (KMS) shifts responsibility for selecting and setting up the graphics mode from to the kernel. When is started, it then detects and uses the mode without any further mode changes. This promises to make booting faster, more graphical, and less flickery.

If KMS were to fail, I would think that X would do its own modesetting; instead of having the kernel do it. But that might require you to first disable KMS. More information specifically for different graphics gards can be found on the Ubuntu Wiki article I linked to eariler.

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