[RFC, drm-misc-next v4 5/9] drm/i915: Implement .be_primary() callback

[Sui Jingfeng <sui.jingfeng@linux.dev>]

From: Sui Jingfeng <suijingfeng@loongson.cn>

On a machine with multiple GPUs, a Linux user has no control over which one
is primary at boot time. This patch tries to solve the mentioned problem by
implementing the .be_primary() callback. Pass i915.modeset=10 on the kernel
cmd line if you really want the device bound by i915 drm driver to be the
primary video adapter, no matter what VGAARB say.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
---
 drivers/gpu/drm/i915/display/intel_vga.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_vga.c b/drivers/gpu/drm/i915/display/intel_vga.c
index 98d7d4dffe9f..e3f78ba2668b 100644
--- a/drivers/gpu/drm/i915/display/intel_vga.c
+++ b/drivers/gpu/drm/i915/display/intel_vga.c
@@ -113,6 +113,17 @@ intel_vga_set_decode(struct pci_dev *pdev, bool enable_decode)
 		return VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;
 }
 
+static bool intel_want_to_be_primary(struct pci_dev *pdev)
+{
+	struct drm_i915_private *i915 = pdev_to_i915(pdev);
+	struct i915_params *params = &i915->params;
+
+	if (params->modeset == 10)
+		return true;
+
+	return false;
+}
+
 int intel_vga_register(struct drm_i915_private *i915)
 {
 	struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
@@ -126,7 +137,8 @@ int intel_vga_register(struct drm_i915_private *i915)
 	 * then we do not take part in VGA arbitration and the
 	 * vga_client_register() fails with -ENODEV.
 	 */
-	ret = vga_client_register(pdev, intel_vga_set_decode, NULL);
+	ret = vga_client_register(pdev, intel_vga_set_decode,
+				  intel_want_to_be_primary);
 	if (ret && ret != -ENODEV)
 		return ret;
 
-- 
2.34.1