[PATCH] [RFC PATCH] DRM: add DRM Driver for Samsung SoC EXYNOS4210.

[daeinki]

Hi, Sascha Hauer.
thank you for your comments and below is my answer.

Sascha Hauer wrote:
> Hi,
> 
> On Fri, Jul 29, 2011 at 04:24:35PM +0900, Inki Dae wrote:
>> This patch is a DRM Driver(only including FIMD Driver yet)
>> for Samsung SoC Exynos4210. and as RFC, I am sending only DRM driver part.
>>
>> this patch is based on git repository below:
>> git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6.git,
>> branch: drm-next
>> commit-id: 5a96a899bbdee86024ab9ea6d02b9e242faacbed
>>
>> We tried to re-use lowlevel codes of the FIMD driver(s3c-fb.c
>> based on Linux framebuffer) but couldn't so because lowlevel codes
>> of s3c-fb.c are included internally and so this driver shares only
>> platform device.
>>
>> Sub drivers such as fimd or hdmi have indenpendent platform device and
>> Platform driver and when driver's probe is called, the driver object
>> including callbacks(for hardware control) would be registered to
>> Samsung drm driver. and then when samsung drm driver is probed,
>> each probe callback of the driver object registered is called so that
>> additional callbacks for drm framework would be set at this time.
>>
>> We used GEM framework for buffer management and this driver supports
>> only physically continuous memory yet(non-iommu). and for buffer allocation,
>> we used DMA APIs(dma_alloc_writecombine) but we will change it to CMA instead
>> of DMA APIs later.
>>
>> Refer to this link for CMA(Continuous Memory Allocator):
>> http://lkml.org/lkml/2011/7/20/45
>>
>> Future works:
>> - HDMI support.
>> - drm plane feature support.
>>   refer to this link for drm plane feature:
>>   http://www.spinics.net/lists/dri-devel/msg11778.html
>> - change the allocator to CMA.
>> - iommu support.(for non-continuous physical memory usage)
>> - fimd driver update.
>> - add exception codes and code clean.
>>
>> to support all features above, we need long time and hard work.
>> so we wish that only some features(fimd and non-iommu) are applied to
>> mainline first.
>>
>> We would be pleased you to give us your comments.
> 
> So far I only had a quick look over the driver. You might know that
> I wrote a Freescale i.MX drm driver which I posted to the list some time
> ago.
> 
> My driver lacks GEM support which your driver has, so I specifically
> looked at this part. It seems we could reuse the GEM code on i.MX and
> probably on most other ARMs aswell. Can you split out this code
> and remove the samsung_ namespace?
> 
By any chance, you mean drm_gem_free_mmap_offset()?
this patch had already been posted by Rob Clark, Omap TI as RFC.

you can refer to this link for it.
http://www.spinics.net/lists/dri-devel/msg13018.html

if so, I am aware of it but his patch isn't applied to drm-next yet and 
so my drm driver doesn't include his patch. of course I will reuse it 
and remove the samsung_ namespace as you pointed out if the patch is 
applied to drm-next.

> btw you should probably Cc the arm Linux Kernel mailing list as this
> is the list where your users are.
> 
> I look forward to have the first ARM drm drivers mainline, so I really
> appreciate your work :)
> 
> Sascha
> 

Thank you for your comments and advice again. :)