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37 .Nd support for Apple laptops with dual GPUs
39 To enable support of dual GPUs in kernel, include the following
40 line in the kernel configuration file:
41 .Bd -ragged -offset indent
42 .Cd "options VGA_SWITCHEROO"
45 When the system has booted, load the apple_gmux
46 driver before the native graphics drivers, for example
49 Alternatively, you can put these two lines in
51 .Bd -literal -offset indent
56 As a result, vga_switcheroo switches the gmux controller so that all
57 output comes from the IGD.
59 Apple MacBook Pro laptops have hybrid graphics, i.e.\& two GPUs, one being
60 the integrated graphics device (IGD) and the other being the discrete
61 graphics device (DIS), sometimes called the dedicated graphics device.
62 Gmux is a microcontroller that controls the output of these GPUs.
65 is the higher level module that facilitates switching between the two
66 GPUs using the lower level
69 When the system boots and
74 It then acts as a handler.
75 The two graphics adapters will also detect the presence of
77 and register as clients.
78 .Sh IMPLEMENTATION NOTES
81 specific implementation, upon detecting the presence of
83 the Intel driver will call
85 to switch the gmux so that all output comes from the IGD.
86 Switching to DIS is not yet supported.
88 Apple MacBook Pro laptops with dual GPUs.
93 .Pa https://01.org/linuxgraphics/gfx-docs/drm/gpu/vga-switcheroo.html
106 He also wrote this manual page.