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Short summary about selecting a glx implementation
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==================================================
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To switch between the GLX implementation from MESA, NVIDIA and AMD(fglrx),
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update-alternatives --config glx
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Detailed description of the diversions/alternatives for libGL.so.1 etc.
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=======================================================================
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The GPU vendors NVIDIA and AMD provide proprietary drivers including GLX
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acceleration for their hardware. Therefore they need to replace the free
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implementation of libGL.so.* (from MESA) and the X.Org module libglx.so with
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a vendor implementation. NVIDIA furthermore maintains several legacy driver
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versions that support older hardware.
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Simply packaging all of them and having each packaging divert the files that
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are going to be replaced (as it was done in the past) causes several
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- All the packages conflict with each other, so only one driver can be
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installed at a time and it can only be disabled (i.e. switching back to
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MESA) by uninstalling the driver again.
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- While a single driver should be sufficient for e.g. a normal desktop
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system, it is insufficient for e.g. a live CD (which would have to
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detect the GPU, select the appropriate driver and libraries and
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configure X.Org accordingly at boot).
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- The rather complicated code maintaining the diversions is duplicated
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Therefore we changed this in the following way:
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- Only one package (glx-diversions) handles the diversions, any package
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requiring the diversions of libGL.so*, libglx.so needs to declare a
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dependency on this package.
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- Vendor implementations are installed into a private library directory
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instead of the locations of the diverted files. This allows parallel
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installation of different drivers without becoming active immediately.
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- To activate an implementation (and to allow easy switching between them)
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an alternative "glx" is being registered with slave alternatives for all
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the libraries, modules and other files of that implementation. This is
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handled by the glx-alternative-{mesa,nvidia,fglrx} packages.
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- As the implementations are split into several packages and optional
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packages may be installed/removed later on, triggers are being used to
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automatically update the alternatives whenever files of that vendor
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implementation are added or removed.
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To switch between the GLX implementation from MESA, NVIDIA and AMD(fglrx),
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update-alternatives --config glx
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For NVIDIA an additional alternative exists that allows one to switch
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between the current driver and legacy versions. For selection use the
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update-alternatives --config nvidia
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The actual list of choices of course depends on the packages currently
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installed on the system.
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The libGL.so link is managed by a dpkg trigger as an alternative, too.
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But there are no alternative solutions available besides the diverted link
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from the libgl1-mesa-dev package (if this package is installed), so this
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cannot be reconfigured. The intention behind this is to always link an
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application at compile time to the MESA implementation of libGL.so.1 in
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order to produce portable binaries, but to use the accelerated libGL.so.1
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when the application is being executed.
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-- Andreas Beckmann <debian@abeckmann.de> Wed, 22 Jun 2011 12:44:11 +0200
added
removed
debian/glx-diversions.README.Debian
