Hello,
TL;DR: how can I set a 8960x2880 screen (not display) size on a T580? A patch for i915 that I found on the internets does not seem to work.
Full story:
I'm a rather happy user of ThinkPad T580 which comes with a high-density 3840x2160 LCD, and the following graphics hardware.
00:02.0 VGA compatible controller: Intel Corporation Device 5917 (rev 07) (prog-if 00 [VGA controller])
Subsystem: Lenovo Device 225a
Flags: bus master, fast devsel, latency 0, IRQ 142
Memory at e7000000 (64-bit, non-prefetchable) [size=16M]
Memory at c0000000 (64-bit, prefetchable) [size=256M]
I/O ports at e000 [size=64]
[virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
Capabilities: [40] Vendor Specific Information: Len=0c <?>
Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
Capabilities: [d0] Power Management version 2
Capabilities: [100] Process Address Space ID (PASID)
Capabilities: [200] Address Translation Service (ATS)
Capabilities: [300] Page Request Interface (PRI)
Kernel driver in use: i915
Kernel modules: i915
Unfortunately attaching it to an external normal-density 2560x1440 display means I need to apply scaling. Combined with the side-by-side arrangement of monitors, this means I'd need to set screen size to 8960x2880. However this does not work:
$ xrandr --fb 8960x2880
xrandr: screen cannot be larger than 8192x8192 (desired size 8960x2880)
I found this thread on reddit about the same problem, where a user posted a simple patch claimed to be supplied by someone on #intel-gfx. Unfortunately it does not work (or at least is not sufficient) - after applying it xrandr does claim that 16384x16384 is possible, but actually trying to use more than 8192x8192 fails with an error (unfortunately I lost the exact message).
My current workaround is to pretend that the displays are arranged vertically, but even after a few months I'm sometimes having trouble remembering that I need to move mouse cursor UP when I want to go to LEFT display :-)
I wonder if someone could help me here. Even just getting a definite answer on whether my hardware can in theory support this or not would be helpful, since I found conflicting information.
FWIW I'm on Debian stable, Linux 4.9.8x.
regards,
Marcin
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