Hi Geert & Sukrut,
On 11/21/25 11:03, Geert Uytterhoeven wrote:
On Thu, 20 Nov 2025 at 19:03, Sukrut Heroorkar <[email protected]> wrote:
The q40fb driver uses a fixed physical address but never reserves
the corresponding I/O region. Reserve the range as suggested in
Documentation/gpu/todo.rst ("Request memory regions in all fbdev drivers").
If the memory cannot be reserved, fail probe with -EBUSY to avoid
conflicting with another user of the same address.
Signed-off-by: Sukrut Heroorkar <[email protected]>
Thanks for your patch!
---
Testing: This patch is sent as RFT since Q40 hardware is unavilable and
QEMU does not emulated a Q40 platform. The change is therefore compile-tested
only.
I would suggest not to apply this, unless it is tested on real
hardware. It wouldn't be the first time an innocent-looking change like
this breaks a system. See e.g.
https://lore.kernel.org/all/[email protected]
Geert, that's actually my thought as well, so I'm happy you wrote down
your opinion here!
By any chance, do you (or someone on this list) know of someone who has
that card and might be able to test it?
Helge
--- a/drivers/video/fbdev/q40fb.c
+++ b/drivers/video/fbdev/q40fb.c
@@ -101,6 +101,13 @@ static int q40fb_probe(struct platform_device *dev)
info->par = NULL;
info->screen_base = (char *) q40fb_fix.smem_start;
+ if (!request_mem_region(q40fb_fix.smem_start, q40fb_fix.smem_len,
+ "q40fb")) {
+ dev_err(&dev->dev, "cannot reserve video memory at 0x%lx\n",
+ q40fb_fix.smem_start);
+ return -EBUSY;
+ }
+
if (fb_alloc_cmap(&info->cmap, 256, 0) < 0) {
framebuffer_release(info);
return -ENOMEM;
