[PATCH v2 12/26] drm/exynos: Split manager/display/subdrv

[Inki Dae]

Sorry for some typos.

2013/10/24 Inki Dae <inki.dae at samsung.com>:
> 2013/10/23 Rob Clark <robdclark at gmail.com>:
>> On Wed, Oct 23, 2013 at 9:18 AM, Inki Dae <inki.dae at samsung.com> wrote:
>>> Look at omapdrm, nouveau, and radeon drm drivers.
>>
>>
>> btw, please don't look at omapdrm as a "good" example in this regard.
>> The layering is really not a good idea and for a long time caused a
>> lot of problems, which we essentially solved by bypassing parts of the
>> layering.  I still think omapdss and omapdrm should be flattened into
>> a single drm driver, then net result would be a drop in # of lines of
>
> It seems that you proper to use duplicated driver. I mean... do you

s/proper/prefer

> proper that omapdss driver is placed in drm framework? Otherwise, is

s/proper/prefer

> there any way that omapdss and omapdrm can be flattened into a single
> drm driver without moving omapdss into drm framework? As I mentioned
> earlier, we wanted to reuse the existing panel driver so Exynos drm
> framework has the layer, wrappers to connector and encoder. Of course,
> for this, we have TODO works yet, and I still think it's better way to
> keep the wrapper if we should reuse the existing panel drivers.
>
> The below would be one design for the case,
>
>
>                                                               lcd panel drivers
>                                                                       \ | /
>                                    drm framework  -----  drm_bridge
>                                                                       / | \
>                                                       crtc
> drivers(display controller or hdmi)
>
>
> A header file of drm_bridge includes drm_panel structure having some
> callbacks related to connector, and some function to register crtc and
> panel driver's requests to the drm_bridge object. And the header file
> can be included in the existing panel drivers. In other words,
> drm_bridge will connect drm driver and lcd class based panel drivers.
>
> struct drm_bridge {
>         struct list_head list;
>         unsigned int type;
>         struct drm_device *drm_dev;
>         struct drm_panel *panel_ops;
>         ...
>         int (*drm_create_enc_conn)(....);
> };
>
> A drm_bridge object has drm_panel ops and drm_create_enc_conn
> callback. And once the crtc driver calls register function of the
> drm_bridge with drm_create_enc_conn callback pointer, a drm_crtc is
> created, and once the panel driver calls the register function with
> drm_panel ops, a encoder and a connector are created. At this time,
> drm_fb_helper_initial_config() can be called appropriately to connect
> crtc and connector, and to display framebuffer on lcd panel.
>
> The above is just my opinion for the case, and we are testing this way
> implementing it internally.
>
> Thanks,
> Inki Dae
>
>> code.  I wish there were folks like the Sean and Stéphane who cared
>> enough to do this for omapdrm ;-)
>>
>> Other drivers have some modularity to separate code that is
>> significantly different across genarations (but what form that takes
>> differs depending on what how the hw differs across generations).
>> This isn't a bad thing.  But you need to look at the end result.  For
>> example how I split out the phy code for the mdp4 code in msm (hdmi
>> and dsi phy differ between otherwise similar 28nm and 45nm parts, but
>> the rest of the display controller blocks are basically the same).
>>
>> BR,
>> -R
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