Preparing more udlfb patches for linux-next

There are limits on how much a small device company can and should do in contributing to open source driver support. But with a historical connection to DisplayLink and more products coming with the technology included, contributing what we can to the generic DisplayLink driver on Linux makes some sense.

Also note this driver is just a foundation on which other stuff (like X) sits, so it doesn’t mean Linux is easy for real end users yet. But it’s getting closer.

Here’s the announce that went to the list today:

The next patch series for udlfb is “nearly ready” for submission, hopefully will be coming in the next few days.

Testing and any problem reports would be helpful. The code that will be submitted is at http://git.plugable.com/gitphp/index.php?p=udlfb&a=summary

There are many dozens of checkins in git as inter-related problems have been explored and the code incrementally improved. Before submitting, I’ll be reconstituting them into a smaller number of more analyzable email patches: make everything checkpatch.pl clean, reorganize things to match final layout, then per-feature patches. We’ll see how that goes.

Major features:

* Support for standard fbdev clients (via defio)
* Improved performance (about 20% average improvement over a variety of “benchmarks” like x11perf, gtkperf, glxgears)
* Asynchronous urb dispatch and no mutexes held for extended periods during render
* Slightly lower CPU consumption, less touching memory, slightly higher average compression
* Better handling of switching from X to fbcon VTs and back
* Driver should unload cleanly from either bottom-up (USB removal) or top-down (shutdown). Problem reports welcome.
* Performance metrics reported through sysfs (read /sys/class/graphics/fbX/*metrics*)
* EDID reported through sysfs (read /sys/class/graphics/graphics/fbX/edid)
* Can compile as module with or without defio or sys_ dependencies
* Lots of cleanup – tested on 64-bit, closer to endian clean, checkpatch.pl clean

What it does not have:

* The defio rendering problems (e.g. with xf86-video-fbdev X server) are still unsolved
* Still 16bpp only. Pseudo-truecolor 32->16 is on the wishlist.
* No DL 1×5 SKU detection yet (you’ll get a blank screen if your monitor’s res exceeds the adapter)

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