linux-kernel - [PATCH v8 06/10] vgaarb: Move disabled VGA device detection to ADD

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Date:   Wed,  5 Jan 2022 18:06:54 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>
Cc:     Xuefeng Li <lixuefeng@...ngson.cn>,
        Huacai Chen <chenhuacai@...il.com>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        linux-pci@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Daniel Axtens <dja@...ens.net>,
        Zhou Wang <wangzhou1@...ilicon.com>
Subject: [PATCH v8 06/10] vgaarb: Move disabled VGA device detection to ADD_DEVICE path

From: Bjorn Helgaas <bhelgaas@...gle.com>

a37c0f48950b ("vgaarb: Select a default VGA device even if there's no
legacy VGA") extended the vga_arb_device_init() subsys_initcall so that if
there are no other eligible devices, it could select a disabled VGA device
as the default.

Move this detection from vga_arb_select_default_device() to
vga_arbiter_add_pci_device() so every device, even those hot-added or
enumerated after vga_arb_device_init() is eligible for selection as the
default VGA device.

Link: https://lore.kernel.org/r/20211015061512.2941859-5-chenhuacai@loongson.cn
Based-on-patch-by: Huacai Chen <chenhuacai@...nel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Daniel Axtens <dja@...ens.net>
Cc: Zhou Wang <wangzhou1@...ilicon.com>
---
 drivers/gpu/vga/vgaarb.c | 27 +++++++++------------------
 1 file changed, 9 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index 123b81628061..ad548917e602 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -656,7 +656,8 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
 	 * We use the first one we find, so if we've already found one,
 	 * vgadev is no better.
 	 */
-	if (boot_vga)
+	if (boot_vga &&
+	    (boot_vga->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)
 		return false;
 
 	if ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK)
@@ -693,6 +694,13 @@ static bool vga_is_boot_device(struct vga_device *vgadev)
 		return true;
 	}
 
+	/*
+	 * vgadev has neither IO nor MEM enabled.  If we haven't found any
+	 * other VGA devices, it is the best candidate so far.
+	 */
+	if (!boot_vga)
+		return true;
+
 	return false;
 }
 
@@ -1559,21 +1567,6 @@ static struct miscdevice vga_arb_device = {
 	MISC_DYNAMIC_MINOR, "vga_arbiter", &vga_arb_device_fops
 };
 
-static void __init vga_arb_select_default_device(void)
-{
-	struct vga_device *vgadev;
-
-	if (!vga_default_device()) {
-		vgadev = list_first_entry_or_null(&vga_list,
-						  struct vga_device, list);
-		if (vgadev) {
-			struct device *dev = &vgadev->pdev->dev;
-			vgaarb_info(dev, "setting as boot device (VGA legacy resources not available)\n");
-			vga_set_default_device(vgadev->pdev);
-		}
-	}
-}
-
 static int __init vga_arb_device_init(void)
 {
 	int rc;
@@ -1603,8 +1596,6 @@ static int __init vga_arb_device_init(void)
 			vgaarb_info(dev, "no bridge control possible\n");
 	}
 
-	vga_arb_select_default_device();
-
 	pr_info("loaded\n");
 	return rc;
 }
-- 
2.25.1