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Linux framebuffer support in SDL2
Gustav Melno
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Post Posted: Wed Mar 05, 2014 12:06 pm
I'm writing a video driver for SDL2 which supports Linux framebuffer
access with tslib support. This feaure was removed in SDL2 but I think
it is very useful for embedded systems. Not all of these systems have
opengl. I know there is DirectFB but this is too complicated for a small
system and cross compiling is a libtool hell. I tried a cross
compilation and it was totally broken. So is there anyone out there who
needs the old tslib and framebuffer support in SDL2?
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Linux framebuffer support in SDL2
Ryan C. Gordon
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Post Posted: Wed Mar 05, 2014 3:06 pm
Quote:
So is there anyone out there who needs the old tslib

I had a request a few months ago to restore fbcon support, but I hadn't gotten around to it yet.

Most embedded things either offer fbcon, an X server (!), or some sort of EGL, so I think it's worth adding.

What does tslib add over talking to /dev/fb directly?

--ryan.

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Linux framebuffer support in SDL2
gabomdq


Joined: 28 Jul 2011
Posts: 495
Location: Argentina
Post Posted: Wed Mar 05, 2014 3:37 pm
2014-03-05 12:06 GMT-03:00 Ryan C. Gordon:
Quote:

Quote:
So is there anyone out there who needs the old tslib

I had a request a few months ago to restore fbcon support, but I hadn't gotten around to it yet.

Most embedded things either offer fbcon, an X server (!), or some sort of EGL, so I think it's worth adding.

What does tslib add over talking to /dev/fb directly?

--ryan.


FWIW, I haven't tried this, but Mesa docs indicate that their EGL implementation supports fbdev (http://www.mesa3d.org/egl.html ), so it may be possible to get SDL/OpenGL* (software emulated) running on top of EGL/fbdev with very minor changes to the Raspberry Pi backend (probably just the native window handler passed to EGL needs to change)





--
Gabriel.
Linux framebuffer support in SDL2
Hartley Sweeten
Guest
Post Posted: Wed Mar 05, 2014 4:35 pm
On Wednesday, March 05, 2014 8:06 AM, Ryan C. Gordon wrote:
Quote:
Quote:
So is there anyone out there who needs the old tslib

I had a request a few months ago to restore fbcon support, but I hadn't gotten around to it yet.

The lack of fbcon support is the only reason I have not switched from SDL1.2 to SDL2.

Quote:
Most embedded things either offer fbcon, an X server (!), or some sort of EGL, so I think it's worth adding.

I use SDL1.2 on an embedded iMX35 ARM SoC board. SDL1.2 works great on this with just a BusyBox based
filesystem created by Buildroot. No X server or other heavyweight front end needed. I have also used
SDL1.2 on an EP9307 ARM SoC board with the same success.

Quote:
What does tslib add over talking to /dev/fb directly?

Calibration of the touchscreen mainly.

I'm using a USB touchscreen LCD (800x480) with the iMX35. The raw touchscreen events are almost
unusable. If I remember correctly, the X and Y axis are swapped and one of them is inverted. Using
tslib you just need to run the calibration utility and everything then works perfectly.

Regards,
Hartley

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Linux framebuffer support in SDL2
Gustav Melno
Guest
Post Posted: Wed Mar 05, 2014 6:36 pm
Quote:
I'm using a USB touchscreen LCD (800x480) with the iMX35. The raw touchscreen events are almost
unusable. If I remember correctly, the X and Y axis are swapped and one of them is inverted. Using
tslib you just need to run the calibration utility and everything then works perfectly.
Tslib has a lot of Filters. I agree with that. Resistive touchpanels in noisy environments are unusable without filtering. Unfiltered raw touch coordinates have a lot of jitter. SDL2 is great but I think dropping framebuffer support was a wrong decision. Sometimes you get a chip with a gpu and a patched kernel to handle this gpu. This patch was made for a kernel version I can not use but the patch is very difficult to port. So the only option is to use the Linux framebuffer. I know its a very special case.

Quote:
FWIW, I haven't tried this, but Mesa docs indicate that their EGL
implementation supports fbdev (http://www.mesa3d.org/egl.html ), so it
may be possible to get SDL/OpenGL* (software emulated) running on top
of EGL/fbdev with very minor changes to the Raspberry Pi backend
(probably just the native window handler passed to EGL needs to change)
Thank you I'll give it a try.

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Linux framebuffer support in SDL2
travist


Joined: 07 Oct 2015
Posts: 4
Post Posted: Thu Oct 15, 2015 12:40 am
I apologize for waking up a older thread... but I am really interested in fbcon support in SDL2. Similar to others in the thread I work on embedded systems that we want to avoid the overhead of X11, have a systems that does not support OpenGL and want to keep things simple and avoid DirectFB. I make simple 2D UI so SDL1.2 has worked perfectly with little issues that were not easily resolved with available resources.

To me this is a feature that helps keep SDL very relevant in embedded systems.

I am curious if you were able to accomplish the video driver support and if fbcon might have a chance of making it into SDL2.

Thanks
______
Travis