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Subject: Re: No more new fbdev drivers, please
To: Emil Velikov <emil.l.velikov@gmail.com>
References: <5603EC15.9090605@ti.com> <5607EA9C.7040909@tronnes.org>
 <CACvgo50PpEG3CVBQdMuXEg9TG+mY_Kxnp3OOHMdZ-hxr3Mok5Q@mail.gmail.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-fbdev <linux-fbdev@vger.kernel.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
        Teddy Wang <teddy.wang@siliconmotion.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Dave Airlie <airlied@redhat.com>,
        Sudip Mukherjee <sudipm.mukherjee@gmail.com>
From: =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= <noralf@tronnes.org>
Message-ID: <5609C47A.6030809@tronnes.org>
Date: Tue, 29 Sep 2015 00:51:38 +0200
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Den 27.09.2015 18:08, skrev Emil Velikov:
> Hi all,
>
> On 27 September 2015 at 14:09, Noralf Trønnes <noralf@tronnes.org> wrote:
>> Den 24.09.2015 14:27, skrev Tomi Valkeinen:
>>> Hi all,
>>>
>>> fbdev is (more or less) maintained, but it's a deprecated framework. All
>>> new Linux display drivers should be done on DRM.
>>>
>>> So let's not add any more new fbdev drivers.
>>>
>>> I will continue to maintain the current fbdev drivers, and I don't mind
>>> adding some new features to those current drivers, as long as the amount
>>> of code required to add the features stays sensible.
>>>
>>> I see we have three fbdev drivers in staging: xgifb, fbtft and sm750fb,
>>> and the question is what to do with those.
>>>
>>> xgifb was added in 2010, and is still in staging.
>>>
>>> fbtft looks like maybe some kind of framework on top of fbdev, with
>>> fbtft specific subdrivers... I didn't look at it in detail, but my gut
>>> says "never".
>>
>> I have done some work [1] to try and make fbtft look more like the rest
>> of the kernel (doc [2]), but that work will result in an almost complete
>> rewrite of fbtft.
>  From a very quick skim fbtft looks pretty much like drm/panel. We
> presently have 30+ 'simple' dsi panels, plus a bunch of spi ones. Have
> you had a look at these ?

Thanks, that was useful.
I can use drm_panel to setup the controller (prepare) and do backlight
(enable/disable), but I need a way to send framebuffer changes.
I could do this:

struct tinydrm_panel_funcs {
         int (*update)(struct drm_framebuffer *fb,
                       struct drm_gem_cma_object *cma_obj,
                       unsigned flags, unsigned color,
                       struct drm_clip_rect *clips, unsigned num_clips);
};

struct tinydrm_panel {
         struct drm_panel panel;
         u32 width;
         u32 height;
         void *dev_private;

         const struct tinydrm_panel_funcs *funcs;
};