RE: [PATCH 0/2] V4L/DVB: OMAP_VOUT: Allow omap_vout to build without VRFB

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Hi,

Hiremath, Vaibhav wrote:
>> -----Original Message-----
>> From: Taneja, Archit
>> Sent: Monday, September 06, 2010 9:31 AM
>> To: Hiremath, Vaibhav
>> Cc: linux-omap@xxxxxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx
>> Subject: RE: [PATCH 0/2] V4L/DVB: OMAP_VOUT: Allow omap_vout to build
>> without VRFB 
>> 
>> Hi,
>> 
>> Hiremath, Vaibhav wrote:
>>>> -----Original Message-----
>>>> From: Taneja, Archit
>>>> Sent: Saturday, September 04, 2010 2:12 PM
>>>> To: Hiremath, Vaibhav
>>>> Cc: linux-omap@xxxxxxxxxxxxxxx;
>>> linux-media@xxxxxxxxxxxxxxx; Taneja,
>>>> Archit
>>>> Subject: [PATCH 0/2] V4L/DVB: OMAP_VOUT: Allow omap_vout to build without
>>>> VRFB 
>>>> 
>>>> This lets omap_vout driver build and run without VRFB. It works
>>>> along the lines of the following patch series:
>>>> OMAP: DSS2: OMAPFB: Allow FB_OMAP2 to build without VRFB
>>>> https://patchwork.kernel.org/patch/105371/
>>>> 
>>>> A variable rotation_type is introduced in omapvideo_info like the
>>>> way in omapfb_info to make both vrfb and non vrfb rotation possible.
>>>> 
>>> [Hiremath, Vaibhav] Archit,
>>> 
>>> Currently omap_vout driver only supports VRFB based rotation, it
>>> doesn't support SDMA based rotation (unlike OMAPFB) and neither you patch
>>> adds it.
>> 
>> [Archit]The above description in the git commit is a mistake from my end.
>> The main purpose of the patch is to get omap_vout running without VRFB.
>> 
>> I am not sure if we need to enable SDMA rotation for V4L2 though, we
>> would always have vrfb and tiler on omap3 and omap4 respectively.
> [Hiremath, Vaibhav] No, for me SDMA based rotation doesn't
> make sense, since SDMA rotation suffers from bandwidth issue.
> On OMAPFB it has been observed that, DSS throws FIFO
> underflow error very frequently in SDMA based rotation.
> 
> 
>> 
>> How do you think things should be handled in the non vrfb case? Should we
>> try to get rotation running or should the driver return an error if
>> userspace tries to enable rotation in a non-vrfb mode?
> [Hiremath, Vaibhav] We can handle this in 2 ways,
> 
> - Driver can return -ERANGE error, in case of OMAP4 (or non-vrfb platform)
> 
> - Driver can choose/fall-down 0 degree rotation gracefully
> 
> As per V4L2 spec both options are acceptable.

Thanks for the clarification. I will work on this change.

Archit--
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