[okl4-developer] Is there any double buffering? S3C2410 lcd - FB

[Robert Wetzel]

Hi Dennis,

> I am wondering if there is anything like double buffering inside the
> lcd-output (fb) of the device. I initialize the lcd correctly, I get an
> LCD-Mode returned (480x640 at 10).. I write
> values to the fb, but the display is still black.

You need to "declare" your framebuffer memory section to the vLCD server
by calling virtual_lcd_add_memsection(). Then you can set the FB address
via virtual_lcd_set_fb() and should be able to see "feedback" when
writing to the FB memory in your application.

Double-buffering is another matter, which I got running, but had to
"cripple" the vLCD server in that turn, namely the function called
virtual_lcd_set_fb_impl(). For me it failed at the physmem_info()
call, even though I declared both buffers to the server (and reserved
them via the memsection_create_dma() call); secondly the function
does additional housekeeping like copying the old to the new FB etc,
which is definitively _not_ what you want.

What I haven't tried yet is interrupt handled FB switches. For this,
a 3rd framebuffer can be handy (one FB is displayed, the second is
finished with rendering, the vrefresh-interrupt hasn't fired yet; which
means your software can either wait on a notify from the interrupt
handler or start filling the next screen already, which would be the
3rd one).


Greets and good luck with the vLCD/framebuffer stuff,

Robert


-- 
Robert Wetzel
Software Engineer

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