[PATCH] fbdev: vga16fb: Request memory region.

[PATCH] fbdev: vga16fb: Request memory region.

[Javier Garcia]

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@gmail.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

Re: [PATCH] fbdev: vga16fb: Request memory region.

[Javier Garcia]

Hi,

Helge Deller, any comment on this patch?

---
Javier Garcia


On Thu, 16 Oct 2025 at 19:18, Javier Garcia <rampxxxx@gmail.com> wrote:
>
> 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@gmail.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
>

Re: [PATCH] fbdev: vga16fb: Request memory region.

[Helge Deller]

On 10/27/25 19:02, Javier Garcia wrote:
> Hi,
> 
> Helge Deller, any comment on this patch?

Well, it doesn't hurt, as it will not abort (as before) even if the region is occupied.
In that sense, I don't see a problem to add it.

But you are missing to release the memory when the driver is released
via vga16fb_remove.

If you send an updated/fixed patch I will apply it to the fbdev tree
to get some testing.

Helge

  
> ---
> Javier Garcia
> 
> 
> On Thu, 16 Oct 2025 at 19:18, Javier Garcia <rampxxxx@gmail.com> wrote:
>>
>> 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@gmail.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
>>

[PATCH v2] fbdev: vga16fb: Request memory region.

[Javier Garcia]

This patch reserve and release VGA memory region.

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

I've tested with 32bits kernel and qemu.

Signed-off-by: Javier Garcia <rampxxxx@gmail.com>
---
v1 -> v2:
      * Add release in vga16fb_remove , thanks Helge Deller.
      * v1 https://lore.kernel.org/lkml/20251016171845.1397153-1-rampxxxx@gmail.com/

 drivers/video/fbdev/vga16fb.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/video/fbdev/vga16fb.c b/drivers/video/fbdev/vga16fb.c
index eedab14c7d51..208e3eefb3ff 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;
 }
 
@@ -1407,6 +1414,8 @@ static void vga16fb_remove(struct platform_device *dev)
 
 	if (info)
 		unregister_framebuffer(info);
+	release_mem_region(vga16fb_fix.smem_start,
+		    vga16fb_fix.smem_len);
 }
 
 static const struct platform_device_id vga16fb_driver_id_table[] = {
-- 
2.50.1

Re: [PATCH v2] fbdev: vga16fb: Request memory region.

[Helge Deller]

On 10/28/25 20:16, Javier Garcia wrote:
> This patch reserve and release VGA memory region.
> 
> This align with Documentation/drm/todo.rst
> "Request memory regions in all fbdev drivers"
> 
> I've tested with 32bits kernel and qemu.
> 
> Signed-off-by: Javier Garcia <rampxxxx@gmail.com>
> ---
> v1 -> v2:
>        * Add release in vga16fb_remove , thanks Helge Deller.
>        * v1 https://lore.kernel.org/lkml/20251016171845.1397153-1-rampxxxx@gmail.com/
> 
>   drivers/video/fbdev/vga16fb.c | 9 +++++++++
>   1 file changed, 9 insertions(+)

applied.

Thanks!
Helge