[android-porting] dobule framebuffer problem when porting android on versatile

[阿磊]

I have a platform, that is versatile, arm926ejs.
I want to porting android on this platform, but failed.
I just get a blank screen after launching /init.
The log message from strace is "writev(4, [{"\5", 1},
{"EGLDisplaySurface\", 18}, {"page flipping not supported
(yres_virtual=640, requested=1280)\", 63}], 3) = 82".
I thought I have a page flipping problem. Therefore, I want to insert
some code in amba-clcd driver to support double framebuffer.
In fact, I have inserted some codes after I referenced other work on
double framebuffer.
e.g.

http://elinux.org/Android_on_OMAP#Page_flipping_frame_buffer

http://androidzaurus.seesaa.net/article/87808061.html

Although, I added the pan function and changed the properties of some
variables, it still doesn't work. I still get the page flipping not
supported message.

Did anyone try to port android on versatile platform?
Could you give me some suggestion?
Thank you in advance.

[阿磊]

I find the problem.

Because there is a set statement in "include/linux/amba/clcd.h"

"var->yres_virtual = var->yres = (var->yres + 1) & ~1;"

It is a wrong statement, because it reset the yres_virtual.

So the android framework will cause page flipping problem.

I insert "var->yres_virtual = var->yres *2; " in "clcd.h" to avoid the
problem occurring.

Now, I can see android's screen on versatile.