Re: [directfb-users] DirectFB without FBDev

Brian G. Rhodes wrote:

quoted

Furthermore, the pan_display functionality could be enhanced to allow 
a kernel side queue
for frame accurate display of several buffers, e.g. video playback 
with five or more buffers
pre-rendered. A frame/sync counter and some new flags would be enough 
to be added for this.
  Ville Syrjala once did an extension like FBIO_FLIP or similar, maybe 
he can elaborate.

I'm also seeing the need to have one pool of memory used by different 
frame buffer devices
or some other way to support multiple layers without statically 
partitioning memory that could
be managed more intelligently.

And how about such capabilities like layer opacity, alpha ramps...?

I know all this was not required to run the kernel based terminal 
emulation that the frame
buffer device has been invented for :)

  

I don't think the solution to abstracting access to multiple hardware 
planes which can be located in at dynamic memory addresses to be 
implemented by adding complexity to the framebuffer driver.  It is 
supposed to be just a dumb chunk of memory and storage for hardware 
timings.

Adding the byte offset and pitch fits into this as well and would save
it from being removed from DirectFB.

Considering video, and the amount of data which has to be shuffled 
around for higher resolution/bitrate files it does not make sense to 
require sending rendered frames off directly to a framebuffer device.  

I was not talking about copying any data back and forth, but just keep
a queue of start addresses assigned to future sync counters, being taken
care of in IRQs.

It is too inefficient and in cases with hardware-assist (other than 
coprocessors), likely unnecessary.  The answer probably isn't using 
Video4Linux directly either.  Perhaps a DirectFB kernel component which 
can standardize an interface and provide a better architecture than v4l2 
does.  An application where, as mentioned above, you are using video 
memory for multiple buffers as a implementation for queuing seems too 
specialized to me to ever be done in a linuxfb driver.

It's not special regarding the hardware. Every driver with an interrupt
handler could support it.

Has any thought been given to designing a DirectFB kernel-space 
component which abstracts that access at the kernel level?  Seems to me 
that it would make direct interaction from directfb with specialized 
hardware much easier.

I don't think a new kernel graphics interface should be added, instead using
UIO to access MMIO, DMA and IRQs would be enough and implement most of the
graphics driver in user space. Downside is to loose the kernel console which
you usually don't need on an embedded device...

For acceleration and DMA/IRQ based programming, I still need to check if a
user space approach would be enough. So far I always handled IRQs in kernel
space for timing/performance reasons...

-- 
Best regards,
   Denis Oliver Kropp

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