linux-kernel - [PATCH] fbdev: vga16fb: Request memory region.

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Message-ID: <20251016171845.1397153-1-rampxxxx@gmail.com>
Date: Thu, 16 Oct 2025 19:18:45 +0200
From: Javier Garcia <rampxxxx@...il.com>
To: deller@....de
Cc: linux-fbdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	shuah@...nel.org,
	Javier Garcia <rampxxxx@...il.com>
Subject: [PATCH] fbdev: vga16fb: Request memory region.

This patch reserve and release VGA memory region with `*_mem_region`
fn's.

This align with Documentation/drm/todo.rst
"Request memory regions in all fbdev drivers"

I've tested with kernel and qemu both 32bits.

Signed-off-by: Javier Garcia <rampxxxx@...il.com>
---

When I've run the code always return -EBUSY which makes sense as
mem is already requested,`/proc/iomem` shows `000a0000-000bffff : Video RAM area`.

I've seen that `cirrusfb` has this kind of code wrapped up with `#if 0`, and I
wonder if it makes sense to also wrap up with `#if 0`, at least , in
that way the code gets commented about expected behavior.


 drivers/video/fbdev/vga16fb.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/video/fbdev/vga16fb.c b/drivers/video/fbdev/vga16fb.c
index eedab14c7d51..f506bf144a97 100644
--- a/drivers/video/fbdev/vga16fb.c
+++ b/drivers/video/fbdev/vga16fb.c
@@ -1319,6 +1319,11 @@ static int vga16fb_probe(struct platform_device *dev)
 	if (ret)
 		return ret;
 
+	if (!request_mem_region(vga16fb_fix.smem_start, vga16fb_fix.smem_len,
+				"vga16b")) {
+		dev_err(&dev->dev,"vga16b: cannot reserve video memory at 0x%lx\n",
+		       vga16fb_fix.smem_start);
+	}
 	printk(KERN_DEBUG "vga16fb: initializing\n");
 	info = framebuffer_alloc(sizeof(struct vga16fb_par), &dev->dev);
 
@@ -1398,6 +1403,8 @@ static int vga16fb_probe(struct platform_device *dev)
  err_ioremap:
 	framebuffer_release(info);
  err_fb_alloc:
+	release_mem_region(vga16fb_fix.smem_start,
+		    vga16fb_fix.smem_len);
 	return ret;
 }
 
-- 
2.50.1