display driver changes in ev3dev-2.0.0 kernel

[dlech]

In ev3dev-stretch, we are now using the mainline kernel driver for the display on the EV3. Unfortunately, this driver does not have support for monochrome. The video memory now uses a 32 bit per pixel layout (XRGB) instead of the one bit per pixel packed format. The plus side is that the screen is actually two bit per pixel grayscale, so we can actually use that feature now, but it means the current hard-coded LCD code is now broken.

[kortschak]

Does this affect the FatCat display as well?

Is the display still a FB; if it is, then it's just a matter of changing the byte representation in the backend. Otherwise, can you post a link to the driver documentation (probably post anyway).

[dlech]

If only affects EV3. Technically, the driver is a DRM driver, so there other ways to use it, but I don't know anything about it. The fbdev device is still there as a compatibility layer.

$ fbset --info

mode "178x128"
    geometry 178 128 178 128 32
    timings 0 0 0 0 0 0 0
    accel true
    rgba 8/16,8/8,8/0,0/0
endmode

Frame buffer device information:
    Name        : 
    Address     : 0xc4882000
    Size        : 91136
    Type        : PACKED PIXELS
    Visual      : TRUECOLOR
    XPanStep    : 1
    YPanStep    : 1
    YWrapStep   : 0
    LineLength  : 712
    Accelerator : No

[kortschak]

Great! That makes it easy. I try to get to this in the next couple of days.

[kortschak]

Is there a reason for not making the same change for the bb kernel as well? Other than time/priority.

[dlech]

The EVB uses a totally different display, so this has no effect on it.

[kortschak]

@hansodenthal I think you probably want to communicate that to the ev3dev.org project. This is the Go bindings for the EV3.