[RFC, drm-misc-next v4 2/9] drm/nouveau: 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. VGAARB will call back to Nouveau
when the drm/nouveau gets loaded successfully.

Pass nouveau.modeset=10 on the kernel cmd line if you really want the
device bound by Nouveau to be the primary video adapter. This overrides
whatever boot device selected by VGAARB.

Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
---
 drivers/gpu/drm/nouveau/nouveau_vga.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_vga.c b/drivers/gpu/drm/nouveau/nouveau_vga.c
index 162b4f4676c7..4242188667e2 100644
--- a/drivers/gpu/drm/nouveau/nouveau_vga.c
+++ b/drivers/gpu/drm/nouveau/nouveau_vga.c
@@ -80,6 +80,15 @@ nouveau_switcheroo_ops = {
 	.can_switch = nouveau_switcheroo_can_switch,
 };
 
+static bool
+nouveau_want_to_be_primary(struct pci_dev *pdev)
+{
+	if (nouveau_modeset == 10)
+		return true;
+
+	return false;
+}
+
 void
 nouveau_vga_init(struct nouveau_drm *drm)
 {
@@ -92,7 +101,7 @@ nouveau_vga_init(struct nouveau_drm *drm)
 		return;
 	pdev = to_pci_dev(dev->dev);
 
-	vga_client_register(pdev, nouveau_vga_set_decode, NULL);
+	vga_client_register(pdev, nouveau_vga_set_decode, nouveau_want_to_be_primary);
 
 	/* don't register Thunderbolt eGPU with vga_switcheroo */
 	if (pci_is_thunderbolt_attached(pdev))
-- 
2.34.1