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

[Inki Dae]

> -----Original Message-----
> From: Sean Paul [mailto:seanpaul at chromium.org]
> Sent: Monday, October 21, 2013 11:47 PM
> To: Inki Dae
> Cc: dri-devel; Dave Airlie; Tomasz Figa; Stéphane Marchesin
> Subject: Re: [PATCH v2 12/26] drm/exynos: Split manager/display/subdrv
> 
> On Thu, Oct 17, 2013 at 10:31 PM, Inki Dae <inki.dae at samsung.com> wrote:
> >
> >
> >> -----Original Message-----
> >> From: Sean Paul [mailto:seanpaul at chromium.org]
> >> Sent: Thursday, October 17, 2013 11:37 PM
> >> To: Inki Dae
> >> Cc: dri-devel; Dave Airlie; Tomasz Figa; Stéphane Marchesin
> >> Subject: Re: [PATCH v2 12/26] drm/exynos: Split manager/display/subdrv
> >>
> >> On Thu, Oct 17, 2013 at 4:21 AM, Inki Dae <inki.dae at samsung.com> wrote:
> >> >
> >> >
> >> >> -----Original Message-----
> >> >> From: Sean Paul [mailto:seanpaul at chromium.org]
> >> >> Sent: Thursday, October 17, 2013 4:27 AM
> >> >> To: dri-devel at lists.freedesktop.org; inki.dae at samsung.com
> >> >> Cc: airlied at linux.ie; tomasz.figa at gmail.com; marcheu at chromium.org;
> Sean
> >> >> Paul
> >> >> Subject: [PATCH v2 12/26] drm/exynos: Split manager/display/subdrv
> >> >>
> >> >> This patch splits display and manager from subdrv. The result is
> that
> >> >> crtc functions can directly call into manager callbacks and encoder
> >> >> functions can directly call into display callbacks. This will allow
> >> >> us to remove the exynos_drm_hdmi shim and support mixer/hdmi &
> fimd/dp
> >> >> with common code.
> >> >>
> >> >> Signed-off-by: Sean Paul <seanpaul at chromium.org>
> >> >> ---
> >> >>
> >> >> Changes in v2:
> >> >>       - Pass display into display_ops instead of context
> >> >
> >> > Sorry but it seems like more reasonable to pass device object into
> >> > display_ops and manager_ops.
> >> >
> >>
> >>
> >> So you've changed your mind from when you said the following?
> >>
> >> >>> manager->ops->xxx(manager, ...);
> >> >>> display->ops->xxx(display, ...);
> >> >>>
> >> >>> Agree.
> >>
> >
> >
> > True. Before that, My comment was to pass device object into display_ops
> and
> > manager_ops, and then you said the good solution is to pass manager and
> > display to each driver. At that time, I thought no matter how the
> callback
> > is called if the framework doesn't call callbacks of each driver with
> ctx.
> > So I agreed.
> >
> >
> >> It would have been nice if you had changed your mind *before* I
> >> reworked everything. At any rate, I think it's still the right thing
> >> to do.
> >
> > Really sorry about that. And I will add new patch for it so you don't
> need
> > to concern about that.
> >
> >>
> >>
> >> > I'm not sure but display_ops could be implemented in other framework
> >> based
> >> > driver such as CDF based lcd panel driver. So if you pass display -
> it's
> >> > specific to exynos drm framework - into display_ops, the other
> framework
> >> > based driver should include specific exynos drm header.
> >> >
> >>
> >> AFAIK, CDF will not land in its current separate-from-drm form, we
> >> don't need to worry about this. Furthermore, these ops should just go
> >> away and become drm_crtc/drm_encoder/drm_connector funcs anyways.
> >>
> >
> > Can you assure the display_ops never implemented in other framework
> based
> > driver, not CDF? At any rate, I think all possibilities should be
opened.
> >
> 
> I don't think we should let an RFC framework make the code more
> complicated for unclear benefit. By removing manager/display entirely,
> we can get rid of a *lot* of other code that is basically just
> plumbing drm hooks (exynos_drm_connector is a good example).
> 
> >>
> >> > And another one, the patch 6 passes manager object to manager_ops,
> and
> >> for
> >> > this, you made the manager object to be set to driver data;
> >> > platform_set_drvdata(pdev, &manager). That isn't reasonable.
> Generally,
> >> > driver_data would point to device driver's context object.
> >> >
> >>
> >> I'm not sure why this isn't reasonable, but it's a moot point. The
> >> driver data is only used up until we get rid of the pm ops, it needn't
> >> be set at all once things go through dpms.
> >>
> >
> > Generally, device drivers can call its own internal functions, and they
> will
> > call that functions with ctx. However, if you set manager to driver_data
> > then that functions should be called with manager object and also
> internally
> > that functions should get ctx from the manager object. What is the
> purpose
> > of manager? Do you think it's reasonable?
> >
> 
> So, to avoid setting the manager as the drvdata, we could implement
> something like fimd_dpms_ctx(ctx, mode) that takes ctx and the manager
> callback calls it fimd_dpms(mgr, mode) { ctx = mgr->ctx;

It's still better for manager to have device objet, mgr->dev, and each
device driver gets its own context of device object. By doing so, each
device driver would have no any dependency of framework. Just leave it as
the device driver's role to get its own context object.

> fimd_dpms_ctx(ctx, mode); }. Alternatively, you can save a pointer to
> mgr in ctx, but that creates a circular link between the two. IMO,

The device drivers don't really need to know the manager object. So context
doesn't need to have manager. What is the purpose of manager? The purpose
would be for that Exynos framework calls sub driver's callbacks.

> both of those solutions suck :)
> 
> I'd much rather just set drvdata to the manager and call the hook
> directly. Like I said earlier, this is just a temporary step since we
> remove these pm ops later in the patch series.
> 
> Sean
> 
> 
> > Anyway, I'd like to say really sorry about inconvenient again. So I will
> fix
> > it.
> >
> > Thanks,
> > Inki Dae
> >
> >> Sean
> >>
> >>
> >> > Thanks,
> >> > Inki Dae
> >> >
> >