Re: No more new fbdev drivers, please

On Thu, Sep 24, 2015 at 11:21 AM, Austin S Hemmelgarn
[off-list ref] wrote:

On 2015-09-24 08:46, Thomas Petazzoni wrote:

quoted

Hello,

On Thu, 24 Sep 2015 15:27:01 +0300, Tomi Valkeinen wrote:

quoted

fbdev is (more or less) maintained, but it's a deprecated framework. All
new Linux display drivers should be done on DRM.

So let's not add any more new fbdev drivers.

I will continue to maintain the current fbdev drivers, and I don't mind
adding some new features to those current drivers, as long as the amount
of code required to add the features stays sensible.

I see we have three fbdev drivers in staging: xgifb, fbtft and sm750fb,
and the question is what to do with those.

xgifb was added in 2010, and is still in staging.

fbtft looks like maybe some kind of framework on top of fbdev, with
fbtft specific subdrivers... I didn't look at it in detail, but my gut
says "never".

fbtft mainly drives some very simple I2C-based or SPI-based displays,
and DRM is I believe overkill for such displays. Last time I talked
with Laurent Pinchart about such drivers, I believe he said that such
simple drivers could probably continue to use the fbdev subsystem.

I have to agree, using DRM _really_ doesn't make sense for these, the
devices in question are (AFAIK) simple I2C or SPI connected frame-buffer
chips that are hooked up to equally simple TFT displays.  There's no 3d
acceleration at all from what I can tell, there's _very_ limited 2d
acceleration, and most of the stuff that the DRM framework provides
call-backs for would have to be done on the CPU anyway.

Just about all of the acceleration stuff is vendor specific so there's
really nothing you need to provide.  As Daniel noted there are several
drm drivers for simple devices that do not support any kind of 2D or
3D acceleration.  There are no requirements to provide any sort of
acceleration.

Alex