[PATCH 0/3] fbdev: Request memory regions in platform drivers

[PATCH 0/3] fbdev: Request memory regions in platform drivers

[Amit Barzilai]

Several fbdev platform drivers call ioremap() on their hardware MMIO
without first claiming the range via request_mem_region(). This leaves
the kernel resource tree (/proc/iomem) with no record of the mapping,
allowing another driver to silently map the same registers.

This series fixes three platform_device drivers by switching to helpers
that combine resource claiming and ioremap in a single managed call.
cobalt_lcdfb and clps711x-fb are converted to
devm_platform_get_and_ioremap_resource(); goldfishfb is converted to
devm_ioremap_resource(), which also lets us drop the manual iounmap()
calls from the error path and remove function.

For clps711x-fb, resource 1 (the framebuffer range) already used
devm_platform_get_and_ioremap_resource() correctly; this series makes
resource 0 (the MMIO control registers) consistent with it.

This is part of the ongoing effort described in
Documentation/drm/todo.rst ("Request memory regions in all fbdev
drivers").

Amit Barzilai (3):
  fbdev: cobalt_lcdfb: Request memory region
  fbdev: clps711x-fb: Request memory region for MMIO
  fbdev: goldfishfb: Request memory region

 drivers/video/fbdev/clps711x-fb.c  |  9 +++------
 drivers/video/fbdev/cobalt_lcdfb.c | 12 +++---------
 drivers/video/fbdev/goldfishfb.c   |  8 +++-----
 3 files changed, 9 insertions(+), 20 deletions(-)


base-commit: 3f9357c30a44734d45e3093c521d52b2aefb09f5
-- 
2.53.0

[PATCH 1/3] fbdev: cobalt_lcdfb: Request memory region

[Amit Barzilai]

Use devm_platform_get_and_ioremap_resource() instead of open-coding
platform_get_resource() and devm_ioremap() separately. The helper
requests the memory region before mapping it, which registers the range
in /proc/iomem and prevents another driver from mapping the same
registers.

Assisted-by: Claude:claude-sonnet-4-6
---
 drivers/video/fbdev/cobalt_lcdfb.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/video/fbdev/cobalt_lcdfb.c b/drivers/video/fbdev/cobalt_lcdfb.c
index 308967b5096a..f7faa95fefd3 100644
--- a/drivers/video/fbdev/cobalt_lcdfb.c
+++ b/drivers/video/fbdev/cobalt_lcdfb.c
@@ -295,19 +295,13 @@ static int cobalt_lcdfb_probe(struct platform_device *dev)
 	if (!info)
 		return -ENOMEM;
 
-	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
-	if (!res) {
+	info->screen_base = devm_platform_get_and_ioremap_resource(dev, 0, &res);
+	if (IS_ERR(info->screen_base)) {
 		framebuffer_release(info);
-		return -EBUSY;
+		return PTR_ERR(info->screen_base);
 	}
 
 	info->screen_size = resource_size(res);
-	info->screen_base = devm_ioremap(&dev->dev, res->start,
-					 info->screen_size);
-	if (!info->screen_base) {
-		framebuffer_release(info);
-		return -ENOMEM;
-	}
 
 	info->fbops = &cobalt_lcd_fbops;
 	info->fix = cobalt_lcdfb_fix;
-- 
2.53.0

[PATCH 2/3] fbdev: clps711x-fb: Request memory region for MMIO

[Amit Barzilai]

Use devm_platform_get_and_ioremap_resource() for resource 0 (the MMIO
control register range) instead of open-coding platform_get_resource()
and devm_ioremap() separately. The helper requests the memory region
before mapping it, which registers the range in /proc/iomem and prevents
another driver from mapping the same registers.

This makes resource 0 consistent with resource 1 (the framebuffer),
which already uses devm_platform_get_and_ioremap_resource().

Assisted-by: Claude:claude-sonnet-4-6
---
 drivers/video/fbdev/clps711x-fb.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/video/fbdev/clps711x-fb.c b/drivers/video/fbdev/clps711x-fb.c
index 5e61a349a4ab..7a7db7100499 100644
--- a/drivers/video/fbdev/clps711x-fb.c
+++ b/drivers/video/fbdev/clps711x-fb.c
@@ -216,12 +216,9 @@ static int clps711x_fb_probe(struct platform_device *pdev)
 	cfb = info->par;
 	platform_set_drvdata(pdev, info);
 
-	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	if (!res)
-		goto out_fb_release;
-	cfb->base = devm_ioremap(dev, res->start, resource_size(res));
-	if (!cfb->base) {
-		ret = -ENOMEM;
+	cfb->base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(cfb->base)) {
+		ret = PTR_ERR(cfb->base);
 		goto out_fb_release;
 	}
 
-- 
2.53.0

[PATCH 3/3] fbdev: goldfishfb: Request memory region

[Amit Barzilai]

Use devm_ioremap_resource() instead of plain ioremap(). The helper
requests the memory region before mapping it, which registers the range
in /proc/iomem and prevents another driver from mapping the same
registers. As it is device-managed, remove the corresponding iounmap()
calls from the error unwind path and the remove function.

Assisted-by: Claude:claude-sonnet-4-6
---
 drivers/video/fbdev/goldfishfb.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/video/fbdev/goldfishfb.c b/drivers/video/fbdev/goldfishfb.c
index ffe33a36b944..14a7cb0a7a1c 100644
--- a/drivers/video/fbdev/goldfishfb.c
+++ b/drivers/video/fbdev/goldfishfb.c
@@ -194,9 +194,9 @@ static int goldfish_fb_probe(struct platform_device *pdev)
 		ret = -ENODEV;
 		goto err_no_io_base;
 	}
-	fb->reg_base = ioremap(r->start, PAGE_SIZE);
-	if (fb->reg_base == NULL) {
-		ret = -ENOMEM;
+	fb->reg_base = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(fb->reg_base)) {
+		ret = PTR_ERR(fb->reg_base);
 		goto err_no_io_base;
 	}
 
@@ -273,7 +273,6 @@ static int goldfish_fb_probe(struct platform_device *pdev)
 				fb->fb.fix.smem_start);
 err_alloc_screen_base_failed:
 err_no_irq:
-	iounmap(fb->reg_base);
 err_no_io_base:
 	kfree(fb);
 err_fb_alloc_failed:
@@ -291,7 +290,6 @@ static void goldfish_fb_remove(struct platform_device *pdev)
 
 	dma_free_coherent(&pdev->dev, framesize, (void *)fb->fb.screen_base,
 						fb->fb.fix.smem_start);
-	iounmap(fb->reg_base);
 	kfree(fb);
 }
 
-- 
2.53.0

Re: [PATCH 3/3] fbdev: goldfishfb: Request memory region

[Helge Deller]

On 4/20/26 15:44, Amit Barzilai wrote:
> Use devm_ioremap_resource() instead of plain ioremap(). The helper
> requests the memory region before mapping it, which registers the range
> in /proc/iomem and prevents another driver from mapping the same
> registers. As it is device-managed, remove the corresponding iounmap()
> calls from the error unwind path and the remove function.
> 
> Assisted-by: Claude:claude-sonnet-4-6
> ---
>   drivers/video/fbdev/goldfishfb.c | 8 +++-----
>   1 file changed, 3 insertions(+), 5 deletions(-)

It was alreads fixed by another patch upstream...

Helge

Re: [PATCH 1/3] fbdev: cobalt_lcdfb: Request memory region

[Helge Deller]

Hi Amit,

On 4/20/26 15:44, Amit Barzilai wrote:
> Use devm_platform_get_and_ioremap_resource() instead of open-coding
> platform_get_resource() and devm_ioremap() separately. The helper
> requests the memory region before mapping it, which registers the range
> in /proc/iomem and prevents another driver from mapping the same
> registers.
> 
> Assisted-by: Claude:claude-sonnet-4-6

You missed your signed-off line, which I added while applying patches #1 and #2:
Signed-off-by: Amit Barzilai <amit.barzilai22@gmail.com>

Amit, please confirm that you wrote patches #2 and #3 and that you
are OK with the added Signed-off-by line, otherwise I need to drop the patches.

Helge

> ---
>   drivers/video/fbdev/cobalt_lcdfb.c | 12 +++---------
>   1 file changed, 3 insertions(+), 9 deletions(-)

Re: [PATCH 1/3] fbdev: cobalt_lcdfb: Request memory region

[Amit Barzilai]

Hi Helge,

Yes, I wrote all three patches and I am OK with the added Signed-off-by line.
Sorry for the oversight, I'll make sure to include it in future submissions.

Thanks,
Amit