Re: [RFC 0/7] drm/omap: Module parameter for display order configuration

[Pekka Paalanen <ppaalanen@gmail.com>]

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On Tue, 29 Aug 2017 10:32:11 +0300
Peter Ujfalusi <peter.ujfalusi@ti.com> wrote:

> Hi
> 
> The series adds support for changing the order of the displays defined by DT
> display aliases.
> 
> The motivation to do such a thing is that for example the fb emulation is
> treating the first display/crtc as the 'main' display and will create the
> fb emulation based on the first display's properties.
> There are many custom applications using DRM directly and they assume that the
> first connector is the 'main' display.
> Afaik weston provides no means either to change the 'main/preferred' display.

Hi,

that's because Weston does not have a concept of main or preferred
display to begin with.

If what you refer to involves running Weston with the fbdev-backend,
then Weston has nothing to do with the issue. Weston only
uses /dev/fb0, whatever that might be and however that might work, as
set up by the kernel.


Thanks,
pq

> 
> It should be the work of user space application (except the fb emulation) to
> somehow deal with the 'main' display selection for their needs, but
> unfortunately they are not capable of diong so for some reason.
> 
> We have boards with LCD panel and HDMI for example and in DT the LCD is set as
> display0, but in certain useage scenarios it is desired to have the HDMI as the
> 'main' display instead of the LCD.
> 
> With the kernel cmd line parameter it is possible to change the pre defined
> order without recompiling the kernel/DT.
> 
> If the board have two active displays:
> 0 - LCD
> 1 - HDMI
> then:
> omapdrm.displays=0,1 - represents the original order (LCD, HDMI)
> omapdrm.displays=1,0 - represents reverse order (HDMI, LCD)
> omapdrm.displays=0 - only the LCD is enabled
> omapdrm.displays=1 - only the HDMI is enabled
> omapdrm.displays=-1 - disable all displays
> 
> The first 6 patch of the series is doing some generic clean up and prepares the
> code so the display ordering is going to be easy to add.
> 
> Regards,
> Peter
> ---
> Peter Ujfalusi (7):
>   drm/omap: Use devm_kzalloc() to allocate omap_drm_private
>   drm/omap: Allocate drm_device earlier and unref it as last step
>   drm/omap: Manage the usable omap_dss_device list within
>     omap_drm_private
>   drm/omap: Separate the dssdevs array setup from the connect function
>   drm/omap: Do dss_device (display) ordering in omap_drv.c
>   drm/omap: dss: Remove display ordering from dss/display.c
>   drm/omap: Add kernel parameter to specify the desired display order
> 
>  drivers/gpu/drm/omapdrm/dss/display.c |  15 +--
>  drivers/gpu/drm/omapdrm/dss/omapdss.h |   3 -
>  drivers/gpu/drm/omapdrm/omap_drv.c    | 244 ++++++++++++++++++++++++----------
>  drivers/gpu/drm/omapdrm/omap_drv.h    |   3 +
>  4 files changed, 183 insertions(+), 82 deletions(-)
> 


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