On Sat, Sep 8, 2018 at 10:17 PM, Sam Ravnborg <sam@xxxxxxxxxxxx> wrote: > Hi all. > > When working on the DRM driver for Atmel LCDC the first approach > was to use a MFD driver, that had two sub-drivers: > - PWM dirver > - DRM driver > > Feedback was that the PWM feature was too small to warrant a MFD driver. > (There was no consencus on this, but I anyway went ahead). > > So the new approch is much simpler (from a code point of view): > DRM Driver that has one sub-driver > - PWM driver > The PWM driver uses registers in the same memory > range as the DRM driver, so the two drivers uses > the same regmap. > > The PWM driver is located in pwm/ > The DRM driver is located in gpu/drm/atmel > The DRM driver uses platform_device_register_data() to > register the sub-device/driver. > I have yet to see it work, but I think this is the right way > to do it. > > This all looked fine until reality kicked in. > > > There is the following dependency chain (=> depends on): > DRM Driver => Panel => Backlight => PWM => DRM Driver > > The DRM Driver rely indirectly on the DRM driver, which it not OK. > > So the open question is how to fix this dependency challenge? > > 1) Drop the generic backlight driver and implement all pwm/backlight > handling in the driver. > 2) Re-introduce the MFD driver. > 3) ? > > Any good ideas? component.c should be able to cope. The driver that matches for the physical/platform device register the pwm thing, plus a component (for the drm driver, you can start with initializing the drm_device already, except for the panel). The panel registers the other component. the component master then does the final step of registering the overall drm_device. Should all work, only bit you might need is a bit of drm_panel/component.c integration. Iirc there's been discussions about that, but no idea where they are stuck. Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
