sna: Allow pipes to be manually assigned to ZaphodHeads

Assigning pipes to a driver instance is hard as not only do we have a
limited number (so choosing which instances should share CRTCs requires
user intervention) but also some pipes are limited by hardware to
certain outputs and certain modes (and we do not have the full knowledge
of the future configuration to be able to determine where to assign the
CRTC). As usual, when there is no clear answer, punt it to the user.

This expands the ZaphodHeads option to include an optional
comma-separated pipe list followed by a colon before the output list,
e.g.

Section "Device"
        Identifier "Device0"
        Driver "intel"
        Option "ZaphodHeads" "1:LVDS"
        BusID "PCI:0:2:0"
        Screen 0
EndSection

Section "Device"
        Identifier "Device1"
        Driver "intel"
        Option "ZaphodHeads" "0,2:HDMI1,HDMI2,HDMI3"
        BusID "PCI:0:2:0"
        Screen 1
EndSection

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 17 insertions, 1 deletions

diff --git a/man/intel.man b/man/intel.man
index e1b7fb93..318a5b71 100644
--- a/man/intel.man
+++ b/man/intel.man
@@ -344,12 +344,28 @@ Default: 0
 .IP
 Specify the randr output(s) to use with zaphod mode for a particular driver
 instance.  If you set this option you must use it with all instances of the
-driver
+driver. By default, each head is assigned only one CRTC (which limits
+using multiple outputs with that head to cloned mode). CRTC can be manually
+assigned to individual heads by preceding the output names with a comma
+delimited list of pipe numbers followed by a colon. Note that different pipes
+may be limited in their functionality and some outputs may only work with
+different pipes.
 .br
 For example:
+
+.RS
 .B
 Option \*qZaphodHeads\*q \*qLVDS1,VGA1\*q
+
 will assign xrandr outputs LVDS1 and VGA1 to this instance of the driver.
+.RE
+
+.RS
+.B
+Option \*qZaphodHeads\*q \*q0,2:HDMI1,DP2\*q
+
+will assign xrandr outputs HDMI1 and DP2 and CRTCs 0 and 2 to this instance of the driver.
+.RE
 
 .SH OUTPUT CONFIGURATION
 On 830M and better chipsets, the driver supports runtime configuration of