linux-kernel - [PATCH v2] fbdev: arkfb: Request legacy VGA I/O region

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Message-ID: <20251213202239.8772-1-swarajgaikwad1925@gmail.com>
Date: Sat, 13 Dec 2025 20:22:34 +0000
From: Swaraj Gaikwad <swarajgaikwad1925@...il.com>
To: Helge Deller <deller@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hans Verkuil <hverkuil+cisco@...nel.org>,
	Nicolas Dufresne <nicolas.dufresne@...labora.com>,
	Frank Li <Frank.Li@....com>,
	Zi Yan <ziy@...dia.com>,
	Donet Tom <donettom@...ux.ibm.com>,
	Yann Dirson <ydirson@...e.fr>,
	Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	Qianfeng Rong <rongqianfeng@...o.com>,
	Kees Cook <kees@...nel.org>,
	linux-fbdev@...r.kernel.org (open list:FRAMEBUFFER LAYER),
	dri-devel@...ts.freedesktop.org (open list:FRAMEBUFFER LAYER),
	linux-kernel@...r.kernel.org (open list)
Cc: skhan@...uxfoundation.org,
	david.hunter.linux@...il.com,
	Swaraj Gaikwad <swarajgaikwad1925@...il.com>
Subject: [PATCH v2] fbdev: arkfb: Request legacy VGA I/O region

The arkfb driver uses the legacy VGA I/O range (0x3c0+) but does not
request it. This can cause conflicts with other drivers that try to
reserve these ports.

Fix this by using devm_request_region() during the probe function.
This ensures the region is properly reserved and automatically released
on driver detach.

v1: https://lore.kernel.org/lkml/20251213154937.104301-1-swarajgaikwad1925@gmail.com/
Signed-off-by: Swaraj Gaikwad <swarajgaikwad1925@...il.com>
---
v2:
 - Use resource_size(&vga_res) instead of hardcoded 64 * 1024.
 - (Feedback from Kees Cook)

Compile-tested only on x86_64.

 drivers/video/fbdev/arkfb.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/video/fbdev/arkfb.c b/drivers/video/fbdev/arkfb.c
index ec084323115f..24e4c20d1a32 100644
--- a/drivers/video/fbdev/arkfb.c
+++ b/drivers/video/fbdev/arkfb.c
@@ -1018,6 +1018,12 @@ static int ark_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)

 	pcibios_bus_to_resource(dev->bus, &vga_res, &bus_reg);

+	if (!devm_request_region(&dev->dev, vga_res.start, resource_size(&vga_res), "arkfb-vga")) {
+		dev_err(info->device, "cannot reserve legacy VGA ports\n");
+		rc = -EBUSY;
+		goto err_find_mode;
+	}
+
 	par->state.vgabase = (void __iomem *) (unsigned long) vga_res.start;

 	/* FIXME get memsize */

base-commit: a859eca0e4cc96f63ff125dbe5388d961558b0e9
--
2.52.0