While Intel is quick to work on enabling future hardware within their open-source graphics driver stack for Linux, the early support is often buggy and problematic on the early code before the hardware is released. Intel now intends to conceal this early hardware support -- for Valley View and Haswell right now -- behind a run-time variable for toggling the support.
For users of released hardware still running old Linux kernels, the experience can be buggy if it's from early on in the hardware enablement timeline. Intel has been working on Haswell
and Valley View
support in the public spotlight for months with early support already in the Linux kernel, but the quality isn't yet pristine.
Intel will now be hiding this early VLV / HSW support -- along with future hardware -- behind a i915_preliminary_hw_support
module parameter. When booting the Linux kernel with its primitive future hardware support, i915.i915_preliminary_hw_support=1
will need to be set in order for the Intel DRM driver to active on the hardware. This variable is being disabled by default.
The patch with this change, which Daniel Vetter has already pulled into his tree, can be found on the mailing list