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drm/bochs: add the dispi VGA DRM driver - #126
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Add a KMS driver for the Bochs dispi VGA adapter used by QEMU stdvga, Bochs and Simics. The adapter exposes a linear 32bpp framebuffer and a small register window; the driver discovers the PCI device, maps both BARs, and drives the dispi registers, directly or through the legacy 0x1ce/0x1cf index pair, to set the scanout format, pitch and base. The KMS pipeline reads the monitor EDID through the dispi EDID window and falls back to the adapter's reference modes and the boot geometry. The adapter has no hardware cursor, so the driver composites the cursor into the framebuffer and repaints the area under it. The console is handed the scanout; if no usable mode exists, the adapter is put back on the boot mode so simpledrm can keep the console. CONFIG_BOCHS is off by default. Signed-off-by: MicroFish <2609948707@qq.com>
Register the bochs probe behind CONFIG_BOCHS, after the paravirtual GPU drivers and before the framebuffer fallback, so a stdvga adapter takes the console before simpledrm does. Signed-off-by: MicroFish <2609948707@qq.com>
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Summary
Add a KMS driver for the Bochs dispi VGA adapter used by QEMU stdvga, Bochs and Simics.
CONFIG_BOCHSis off by default. The probe is registered after the paravirtual GPU drivers and before the framebuffer fallback, and reports display ownership.Dependencies
Stacked on the
drmcore PR for theprobe(bool *display_owned)signature and the display-ownership handoff.Testing
Builds with
CONFIG_BOCHS=y;bochs.oandbochs_kms.ocompile andbochs_probeis present. The default configuration is unchanged.