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CONFIG_DRM_RADEON_KMS: Enable modesetting on radeon by default - NEW DRIVER

General informations

The Linux kernel configuration item CONFIG_DRM_RADEON_KMS has multiple definitions:

Enable modesetting on radeon by default - NEW DRIVER found in drivers/gpu/drm/radeon/Kconfig

The configuration item CONFIG_DRM_RADEON_KMS:

Help text

Choose this option if you want kernel modesetting enabled by default.

This is a completely new driver. It's only part of the existing drm for compatibility reasons. It requires an entirely different graphics stack above it and works very differently from the old drm stack. i.e. don't enable this unless you know what you are doing it may cause issues or bugs compared to the previous userspace driver stack.

When kernel modesetting is enabled the IOCTL of radeon/drm driver are considered as invalid and an error message is printed in the log and they return failure.

KMS enabled userspace will use new API to talk with the radeon/drm driver. The new API provide functions to create/destroy/share/mmap buffer object which are then managed by the kernel memory manager (here TTM). In order to submit command to the GPU the userspace provide a buffer holding the command stream, along this buffer userspace have to provide a list of buffer object used by the command stream. The kernel radeon driver will then place buffer in GPU accessible memory and will update command stream to reflect the position of the different buffers.

The kernel will also perform security check on command stream provided by the user, we want to catch and forbid any illegal use of the GPU such as DMA into random system memory or into memory not owned by the process supplying the command stream.

Enable modesetting on radeon by default found in drivers/gpu/drm/radeon/Kconfig

The configuration item CONFIG_DRM_RADEON_KMS:

Help text

Choose this option if you want kernel modesetting enabled by default, and you have a new enough userspace to support this. Running old userspaces with this enabled will cause pain.

When kernel modesetting is enabled the IOCTL of radeon/drm driver are considered as invalid and an error message is printed in the log and they return failure.

KMS enabled userspace will use new API to talk with the radeon/drm driver. The new API provide functions to create/destroy/share/mmap buffer object which are then managed by the kernel memory manager (here TTM). In order to submit command to the GPU the userspace provide a buffer holding the command stream, along this buffer userspace have to provide a list of buffer object used by the command stream. The kernel radeon driver will then place buffer in GPU accessible memory and will update command stream to reflect the position of the different buffers.

The kernel will also perform security check on command stream provided by the user, we want to catch and forbid any illegal use of the GPU such as DMA into random system memory or into memory not owned by the process supplying the command stream. This part of the code is still incomplete and this why we propose that patch as a staging driver addition, future security might forbid current experimental userspace to run.

This code support the following hardware : R1XX,R2XX,R3XX,R4XX,R5XX (radeon up to X1950). Works is underway to provide support for R6XX, R7XX and newer hardware (radeon from HD2XXX to HD4XXX).

Hardware

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