On 04/01/17 17:06, Daniel Vetter wrote:
On Wed, Jan 04, 2017 at 02:34:36PM +0100, Noralf Trønnes wrote:
Hi,
I was previously working on tinydrm as a replacement for staging/fbtft.
During a break from that work, I started to think about if it would be
possible to move the drivers to userspace instead. No point in having
them in the kernel if it's not necessary.
This patchset includes all the pieces necessary to get a userspace
driver[1] working that is compatible with the fbtft/fb_ili9341 driver.
It is tested with a SPI interfaced display hat/shield for the Raspberry Pi,
which has an eeprom with a Device Tree fragment on it (merged by the
bootloader). With the help of udev and systemd, the driver is able to
autoload when the display is connected.
Performance wise, the kernel driver can do ~19fps on a 320x240 spi@32MHz
display, whereas the userspace version does ~18fps. So performance is not
an argument to keep the driver in the kernel.
What do you think about this approach?
It's a pretty nifty thing, and iirc some of the ideas for implementing
miracast centered around the same idea: Small userspace drm driver shim
that forwards everything to the miracast code running all in userspace.
David Herrmann looked into that years ago, not sure he ever got the full
stack up&running.
This is actually something David Herrmann told us not to do, stating
that it was too hard for Desktop Environments to select which GPUs to
output to. I however disagreed as this is something they need to support
anyway for USB GPUs and miracast could piggy back on this effort.
An engineer in Intel Finland did work on this and we got approval for
Open Sourcing it but I really have no time for this right now though :s
That was my 2 cents.
Martin
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