[PATCH 11/24] drm/omap: Add kernel parameter to specify the desired display order

[Tomi Valkeinen]

On 27/02/18 15:35, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Monday, 12 February 2018 11:44:41 EET Tomi Valkeinen wrote:
>> From: Peter Ujfalusi <peter.ujfalusi at ti.com>
>>
>> omapdrm.displays (int array) can be used to reorder the displays by id if
>> needed. It can be also used to disable display.
>>
>> 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
> 
> What's the use case for this ?

fbdev uses the first display as "main" display. There are also many apps
using DRM APIs that unfortunately depend on the order, and presume the
first one is the initial or main display. It's also a nice tool for
debugging, so that you can easily fully disable a display or all displays.

 Tomi

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