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bool "Enable modesetting on radeon by default - NEW DRIVER"
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select BACKLIGHT_CLASS_DEVICE
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Choose this option if you want kernel modesetting enabled by default.
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This is a completely new driver. It's only part of the existing drm
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for compatibility reasons. It requires an entirely different graphics
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stack above it and works very differently from the old drm stack.
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i.e. don't enable this unless you know what you are doing it may
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cause issues or bugs compared to the previous userspace driver stack.
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When kernel modesetting is enabled the IOCTL of radeon/drm
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driver are considered as invalid and an error message is printed
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in the log and they return failure.
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KMS enabled userspace will use new API to talk with the radeon/drm
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driver. The new API provide functions to create/destroy/share/mmap
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buffer object which are then managed by the kernel memory manager
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(here TTM). In order to submit command to the GPU the userspace
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provide a buffer holding the command stream, along this buffer
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userspace have to provide a list of buffer object used by the
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command stream. The kernel radeon driver will then place buffer
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in GPU accessible memory and will update command stream to reflect
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the position of the different buffers.
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The kernel will also perform security check on command stream
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provided by the user, we want to catch and forbid any illegal use
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of the GPU such as DMA into random system memory or into memory
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not owned by the process supplying the command stream.