[okl4-developer] gta01 and framebufer

[Geoffrey Lee]

On Mon, May 19, 2008 at 05:37:59PM +0000, Remy Gottschalk wrote:
> Hi all,
> 

Hi Remy


> I am trying to get some display under wombat with gta01 as target. If i
> understood well I have two options : using the Linux native drivers or
> the iguana native drivers plus a stub in Linux.
> 
> For the first solution I found out that the drivers to be used is the
> s3c2410 lcd driver (ie : s3c2410fb). But it depends on ARCH_S3C2410 and
> thus don't seems to be directly usable.
> So i tried to add this arch and enable it with scary results (as
> expected).
> I also tried to forcefully enable the drivers without adding the arch by
> tricking the dependencies. It gives better results and the only thing
> left to compile correctly is that  dma_alloc_writecombine and
> dma_free_writecombine are missing.
> I suppose that it is due to dma not being fully available in wombat.
> 
> So for this option the questions are :
> Is s3c2410fb indeed the correct drivers to use ?


Yes, I believe so. 

> Should it be feasible to make the drivers work without the full arch
> support ?

Yes, I believe so.  You will need to somehow pull in the all the
dependencies of the driver though.  As you have noticed, some of the
functions that this driver depends on are missing.

> If I interpreted correctly the problem, how could I replace the missing
> functions ?

You will need to reimplement in arch/l4 and include/asm-l4.  how they
are implemented will depend on exactly what function you are trying
to re-implement.  In some cases you can base it on a loose equivalent on
the one for the native port, in some cases you may have to rely on using
Iguana / L4 APIs.

> 	
> For the second option. It seems that with the default configuration the
> right iguana native lcd drivers is already activated and running. 
> I assumed that wombat's iguana virtual framebuffer is the corresponding
> stub and started to work with it. It seems that the wombat drivers is
> still designed to use the old drivers framework while the iguana's
> drivers is implemented with the v2 framework.
> So I tried to make the wombat stub evolve (using the serial drivers as
> reference) and I am stuck pretty soon since iguana_getenv("VLCD_TID");
> return NULL. 
> 
> So for this option :
> Are my assumptions correct ? (Is iguana's drivers using v2 and wombat's
> one expecting v1 ?)
> Are VLCD_TID and VLCD_HNDLE supposed to exists or do they need to be
> created ?
> If it needs to be created, how ?

I took a quick look and it appears that the vLCD has been
temporarily disabled in the devicecore.  Have a look at
platform/s3c2410/iguana/devicecore/src/device_core.c.  I

> 
> And more generally I've read a little while that a documentation
> concerning the drivers framework was under works, do you have any news
> concerning this ?

I know there is a driver user manual in the works.  I'll try and see if
I can poke the relevant people to give an answer on the status of that.


> I've also read that you got at one time the framebuffer running on this
> platform (and something concerning quake), how did you achieved that ?

We did have a demo example application using the framebuffer at one
point but to my knowledge we did not ever run Quake on s3c2410-based
platforms.

	-gl

> 
> I hope i managed to be clear.
> 
> Regards,
> 
> -- 
> Remy Gottschalk - rgottschalk at linagora.com
> Ingénieur informatique embarquée
> Groupe LINAGORA - http://www.linagora.com
> Tél.: +33(0)1 58 18 68 28 - Fax : +33(0)1 58 18 68 29
> 
> 
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