[PATCH v2 0/4] fbdev: Make CONFIG_FB_DEVICE optional for drivers

[PATCH v2 0/4] fbdev: Make CONFIG_FB_DEVICE optional for drivers

[Chintan Patel]

This series makes CONFIG_FB_DEVICE optional for fbdev drivers that use
it only for sysfs interfaces, addressing Thomas Zimmermann’s TODO to
remove hard FB_DEVICE dependencies.

The series introduces a small helper, dev_of_fbinfo(), which returns
NULL when CONFIG_FB_DEVICE=n. This allows sysfs code paths to be skipped
via runtime checks, avoids #ifdef CONFIG_FB_DEVICE clutter, and keeps
full compile-time syntax checking.

Changes in v2:
Add dev_of_fbinfo() helper (suggested by Geert Uytterhoeven)
Replace #ifdef CONFIG_FB_DEVICE blocks with runtime NULL checks
Switch to fb_dbg() / fb_info() logging (suggested by Thomas Zimmermann)

Chintan Patel (4):
  fb: Add dev_of_fbinfo() helper for optional sysfs support
  staging: fbtft: Make FB_DEVICE dependency optional
  fbdev: omapfb: Make FB_DEVICE dependency optional
  fbdev: sh_mobile_lcdc: Make FB_DEVICE dependency optional

 drivers/staging/fbtft/Kconfig                  |  5 ++++-
 drivers/staging/fbtft/fbtft-sysfs.c            | 18 ++++++++++++++----
 drivers/video/fbdev/omap2/omapfb/Kconfig       |  3 ++-
 .../video/fbdev/omap2/omapfb/omapfb-sysfs.c    | 16 ++++++++++++----
 drivers/video/fbdev/sh_mobile_lcdcfb.c         |  9 +++++++++
 include/linux/fb.h                             |  9 +++++++++
 6 files changed, 50 insertions(+), 10 deletions(-)

-- 
2.43.0

[PATCH v2 1/4] fb: Add dev_of_fbinfo() helper for optional sysfs support

[Chintan Patel]

Add dev_of_fbinfo() to return the framebuffer struct device when
CONFIG_FB_DEVICE is enabled, or NULL otherwise.

This allows fbdev drivers to use sysfs interfaces via runtime checks
instead of CONFIG_FB_DEVICE ifdefs, keeping the code clean while
remaining fully buildable.

Suggested-by: Helge Deller <deller@gmx.de>
Signed-off-by: Chintan Patel <chintanlike@gmail.com>
---
 include/linux/fb.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/fb.h b/include/linux/fb.h
index 05cc251035da..dad3fb61a06a 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -628,6 +628,15 @@ static inline void unlock_fb_info(struct fb_info *info)
 	mutex_unlock(&info->lock);
 }
 
+static inline struct device *dev_of_fbinfo(const struct fb_info *info)
+{
+#ifdef CONFIG_FB_DEVICE
+	return info->dev;
+#else
+	return NULL;
+#endif
+}
+
 static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,
 					   u8 *src, u32 s_pitch, u32 height)
 {
-- 
2.43.0

Re: [PATCH v2 1/4] fb: Add dev_of_fbinfo() helper for optional sysfs support

[Andy Shevchenko]

On Fri, Dec 19, 2025 at 7:43 AM Chintan Patel <chintanlike@gmail.com> wrote:
>
> Add dev_of_fbinfo() to return the framebuffer struct device when
> CONFIG_FB_DEVICE is enabled, or NULL otherwise.
>
> This allows fbdev drivers to use sysfs interfaces via runtime checks
> instead of CONFIG_FB_DEVICE ifdefs, keeping the code clean while
> remaining fully buildable.

Reviewed-by: Andy Shevchenko <andy@kernel.org>

-- 
With Best Regards,
Andy Shevchenko

[PATCH v2 2/4] staging: fbtft: Make FB_DEVICE dependency optional

[Chintan Patel]

fbtft provides sysfs interfaces for debugging and gamma configuration,
but these are not required for the core driver.

Drop the hard dependency on CONFIG_FB_DEVICE and make sysfs support
optional by using dev_of_fbinfo() at runtime. When FB_DEVICE is disabled,
sysfs operations are skipped while the code remains buildable and
type-checked.

v2:
- Replace CONFIG_FB_DEVICE ifdefs with runtime checks
- Use dev_of_fbinfo() to guard sysfs creation and removal

Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
Suggested-by: Helge Deller <deller@gmx.de>
Signed-off-by: Chintan Patel <chintanlike@gmail.com>
---
 drivers/staging/fbtft/Kconfig       |  5 ++++-
 drivers/staging/fbtft/fbtft-sysfs.c | 18 ++++++++++++++----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/fbtft/Kconfig b/drivers/staging/fbtft/Kconfig
index c2655768209a..578412a2f379 100644
--- a/drivers/staging/fbtft/Kconfig
+++ b/drivers/staging/fbtft/Kconfig
@@ -2,11 +2,14 @@
 menuconfig FB_TFT
 	tristate "Support for small TFT LCD display modules"
 	depends on FB && SPI
-	depends on FB_DEVICE
 	depends on BACKLIGHT_CLASS_DEVICE
 	depends on GPIOLIB || COMPILE_TEST
 	select FB_BACKLIGHT
 	select FB_SYSMEM_HELPERS_DEFERRED
+	help
+	  Support for small TFT LCD display modules over SPI bus. FB_DEVICE
+	  is not required, but if enabled, provides sysfs interface for debugging
+	  and gamma curve configuration.
 
 if FB_TFT
 
diff --git a/drivers/staging/fbtft/fbtft-sysfs.c b/drivers/staging/fbtft/fbtft-sysfs.c
index e45c90a03a90..848702fc871a 100644
--- a/drivers/staging/fbtft/fbtft-sysfs.c
+++ b/drivers/staging/fbtft/fbtft-sysfs.c
@@ -203,14 +203,24 @@ static struct device_attribute debug_device_attr =
 
 void fbtft_sysfs_init(struct fbtft_par *par)
 {
-	device_create_file(par->info->dev, &debug_device_attr);
+	struct device *dev = dev_of_fbinfo(par->info);
+
+	if (!dev)
+		return;
+
+	device_create_file(dev, &debug_device_attr);
 	if (par->gamma.curves && par->fbtftops.set_gamma)
-		device_create_file(par->info->dev, &gamma_device_attrs[0]);
+		device_create_file(dev, &gamma_device_attrs[0]);
 }
 
 void fbtft_sysfs_exit(struct fbtft_par *par)
 {
-	device_remove_file(par->info->dev, &debug_device_attr);
+	struct device *dev = dev_of_fbinfo(par->info);
+
+	if (!dev)
+		return;
+
+	device_remove_file(dev, &debug_device_attr);
 	if (par->gamma.curves && par->fbtftops.set_gamma)
-		device_remove_file(par->info->dev, &gamma_device_attrs[0]);
+		device_remove_file(dev, &gamma_device_attrs[0]);
 }
-- 
2.43.0

Re: [PATCH v2 2/4] staging: fbtft: Make FB_DEVICE dependency optional

[Andy Shevchenko]

On Fri, Dec 19, 2025 at 7:43 AM Chintan Patel <chintanlike@gmail.com> wrote:
>
> fbtft provides sysfs interfaces for debugging and gamma configuration,
> but these are not required for the core driver.
>
> Drop the hard dependency on CONFIG_FB_DEVICE and make sysfs support
> optional by using dev_of_fbinfo() at runtime. When FB_DEVICE is disabled,
> sysfs operations are skipped while the code remains buildable and
> type-checked.
>
> v2:
> - Replace CONFIG_FB_DEVICE ifdefs with runtime checks
> - Use dev_of_fbinfo() to guard sysfs creation and removal
>
> Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
> Suggested-by: Helge Deller <deller@gmx.de>
> Signed-off-by: Chintan Patel <chintanlike@gmail.com>
> ---
>  drivers/staging/fbtft/Kconfig       |  5 ++++-
>  drivers/staging/fbtft/fbtft-sysfs.c | 18 ++++++++++++++----
>  2 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/staging/fbtft/Kconfig b/drivers/staging/fbtft/Kconfig
> index c2655768209a..578412a2f379 100644
> --- a/drivers/staging/fbtft/Kconfig
> +++ b/drivers/staging/fbtft/Kconfig
> @@ -2,11 +2,14 @@
>  menuconfig FB_TFT
>         tristate "Support for small TFT LCD display modules"
>         depends on FB && SPI
> -       depends on FB_DEVICE
>         depends on BACKLIGHT_CLASS_DEVICE
>         depends on GPIOLIB || COMPILE_TEST
>         select FB_BACKLIGHT
>         select FB_SYSMEM_HELPERS_DEFERRED
> +       help
> +         Support for small TFT LCD display modules over SPI bus. FB_DEVICE
> +         is not required, but if enabled, provides sysfs interface for debugging
> +         and gamma curve configuration.
>
>  if FB_TFT
>
> diff --git a/drivers/staging/fbtft/fbtft-sysfs.c b/drivers/staging/fbtft/fbtft-sysfs.c
> index e45c90a03a90..848702fc871a 100644
> --- a/drivers/staging/fbtft/fbtft-sysfs.c
> +++ b/drivers/staging/fbtft/fbtft-sysfs.c
> @@ -203,14 +203,24 @@ static struct device_attribute debug_device_attr =
>
>  void fbtft_sysfs_init(struct fbtft_par *par)
>  {
> -       device_create_file(par->info->dev, &debug_device_attr);
> +       struct device *dev = dev_of_fbinfo(par->info);
> +
> +       if (!dev)
> +               return;
> +
> +       device_create_file(dev, &debug_device_attr);
>         if (par->gamma.curves && par->fbtftops.set_gamma)
> -               device_create_file(par->info->dev, &gamma_device_attrs[0]);
> +               device_create_file(dev, &gamma_device_attrs[0]);
>  }
>
>  void fbtft_sysfs_exit(struct fbtft_par *par)
>  {
> -       device_remove_file(par->info->dev, &debug_device_attr);
> +       struct device *dev = dev_of_fbinfo(par->info);
> +
> +       if (!dev)
> +               return;
> +
> +       device_remove_file(dev, &debug_device_attr);
>         if (par->gamma.curves && par->fbtftops.set_gamma)
> -               device_remove_file(par->info->dev, &gamma_device_attrs[0]);
> +               device_remove_file(dev, &gamma_device_attrs[0]);
>  }
> --
> 2.43.0
>


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/4] staging: fbtft: Make FB_DEVICE dependency optional

[Andy Shevchenko]

On Fri, Dec 19, 2025 at 7:43 AM Chintan Patel <chintanlike@gmail.com> wrote:
>
> fbtft provides sysfs interfaces for debugging and gamma configuration,
> but these are not required for the core driver.
>
> Drop the hard dependency on CONFIG_FB_DEVICE and make sysfs support
> optional by using dev_of_fbinfo() at runtime. When FB_DEVICE is disabled,
> sysfs operations are skipped while the code remains buildable and
> type-checked.

> v2:
> - Replace CONFIG_FB_DEVICE ifdefs with runtime checks
> - Use dev_of_fbinfo() to guard sysfs creation and removal

The place for the change log is either a cover letter, or...

> Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
> Suggested-by: Helge Deller <deller@gmx.de>
> Signed-off-by: Chintan Patel <chintanlike@gmail.com>
> ---

...a comment block here. It's not so important to be in the Git
history since we have a lore.kernel.org archive.

>  drivers/staging/fbtft/Kconfig       |  5 ++++-
>  drivers/staging/fbtft/fbtft-sysfs.c | 18 ++++++++++++++----

...

>  void fbtft_sysfs_init(struct fbtft_par *par)
>  {
> -       device_create_file(par->info->dev, &debug_device_attr);
> +       struct device *dev = dev_of_fbinfo(par->info);
> +
> +       if (!dev)
> +               return;


The better way is to decouple the definition and the assignment in the
cases when it's followed by a conditional (validation check). In this
case any new code added in between doesn't affect readability and
maintenance efforts.

       struct device *dev;

       dev = dev_of_fbinfo(par->info);
       if (!dev)
               return;

> +       device_create_file(dev, &debug_device_attr);
>         if (par->gamma.curves && par->fbtftops.set_gamma)
> -               device_create_file(par->info->dev, &gamma_device_attrs[0]);
> +               device_create_file(dev, &gamma_device_attrs[0]);
>  }

Ditto for the rest.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/4] staging: fbtft: Make FB_DEVICE dependency optional

[Chintan Patel]

Hi Andy,

On 12/27/25 06:19, Andy Shevchenko wrote:
> On Fri, Dec 19, 2025 at 7:43 AM Chintan Patel <chintanlike@gmail.com> wrote:
>>
>> fbtft provides sysfs interfaces for debugging and gamma configuration,
>> but these are not required for the core driver.
>>
>> Drop the hard dependency on CONFIG_FB_DEVICE and make sysfs support
>> optional by using dev_of_fbinfo() at runtime. When FB_DEVICE is disabled,
>> sysfs operations are skipped while the code remains buildable and
>> type-checked.
> 
>> v2:
>> - Replace CONFIG_FB_DEVICE ifdefs with runtime checks
>> - Use dev_of_fbinfo() to guard sysfs creation and removal
> 
> The place for the change log is either a cover letter, or...
> 
>> Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
>> Suggested-by: Helge Deller <deller@gmx.de>
>> Signed-off-by: Chintan Patel <chintanlike@gmail.com>
>> ---
> 
> ...a comment block here. It's not so important to be in the Git
> history since we have a lore.kernel.org archive.

Thank you for suggestion! Will move to coverletter.

>>   drivers/staging/fbtft/Kconfig       |  5 ++++-
>>   drivers/staging/fbtft/fbtft-sysfs.c | 18 ++++++++++++++----
> 
> ...
> 
>>   void fbtft_sysfs_init(struct fbtft_par *par)
>>   {
>> -       device_create_file(par->info->dev, &debug_device_attr);
>> +       struct device *dev = dev_of_fbinfo(par->info);
>> +
>> +       if (!dev)
>> +               return;
> 
> 
> The better way is to decouple the definition and the assignment in the
> cases when it's followed by a conditional (validation check). In this
> case any new code added in between doesn't affect readability and
> maintenance efforts.
> 
>         struct device *dev;
> 
>         dev = dev_of_fbinfo(par->info);
>         if (!dev)
>                 return;
> 
>> +       device_create_file(dev, &debug_device_attr);
>>          if (par->gamma.curves && par->fbtftops.set_gamma)
>> -               device_create_file(par->info->dev, &gamma_device_attrs[0]);
>> +               device_create_file(dev, &gamma_device_attrs[0]);
>>   }
> 
> Ditto for the rest.

Will do v3 and re-send. Thanks for reviews!

[PATCH v2 3/4] fbdev: omapfb: Make FB_DEVICE dependency optional

[Chintan Patel]

omapfb provides several sysfs interfaces for framebuffer configuration
and debugging, but these are not required for the core driver.

Remove the hard dependency on CONFIG_FB_DEVICE and make sysfs support
optional by using dev_of_fbinfo() to obtain the backing device at runtime.
When FB_DEVICE is disabled, sysfs operations are skipped while the code
still builds and is type-checked.

v2:
- Replace CONFIG_FB_DEVICE ifdefs and stubs with runtime checks
- Use dev_of_fbinfo() to skip sysfs when unavailable

Suggested-by: Helge Deller <deller@gmx.de>
Signed-off-by: Chintan Patel <chintanlike@gmail.com>
---
 drivers/video/fbdev/omap2/omapfb/Kconfig        |  3 ++-
 drivers/video/fbdev/omap2/omapfb/omapfb-sysfs.c | 16 ++++++++++++----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/video/fbdev/omap2/omapfb/Kconfig b/drivers/video/fbdev/omap2/omapfb/Kconfig
index f4cdf999a080..2d20e79adefc 100644
--- a/drivers/video/fbdev/omap2/omapfb/Kconfig
+++ b/drivers/video/fbdev/omap2/omapfb/Kconfig
@@ -5,7 +5,6 @@ config OMAP2_VRFB
 menuconfig FB_OMAP2
 	tristate "OMAP2+ frame buffer support"
 	depends on FB
-	depends on FB_DEVICE
 	depends on DRM_OMAP = n
 	depends on GPIOLIB
 	select FB_OMAP2_DSS
@@ -13,6 +12,8 @@ menuconfig FB_OMAP2
 	select FB_IOMEM_HELPERS
 	help
 	  Frame buffer driver for OMAP2+ based boards.
+	  FB_DEVICE is not required, but if enabled, provides sysfs interface
+	  for framebuffer configuration and debugging.
 
 if FB_OMAP2
 
diff --git a/drivers/video/fbdev/omap2/omapfb/omapfb-sysfs.c b/drivers/video/fbdev/omap2/omapfb/omapfb-sysfs.c
index 831b2c2fbdf9..ef555dd598aa 100644
--- a/drivers/video/fbdev/omap2/omapfb/omapfb-sysfs.c
+++ b/drivers/video/fbdev/omap2/omapfb/omapfb-sysfs.c
@@ -558,10 +558,14 @@ int omapfb_create_sysfs(struct omapfb2_device *fbdev)
 
 	DBG("create sysfs for fbs\n");
 	for (i = 0; i < fbdev->num_fbs; i++) {
+		struct device *dev = dev_of_fbinfo(fbdev->fbs[i]);
 		int t;
+
+		if (!dev)
+			continue;
+
 		for (t = 0; t < ARRAY_SIZE(omapfb_attrs); t++) {
-			r = device_create_file(fbdev->fbs[i]->dev,
-					&omapfb_attrs[t]);
+			r = device_create_file(dev, &omapfb_attrs[t]);
 
 			if (r) {
 				dev_err(fbdev->dev, "failed to create sysfs "
@@ -580,9 +584,13 @@ void omapfb_remove_sysfs(struct omapfb2_device *fbdev)
 
 	DBG("remove sysfs for fbs\n");
 	for (i = 0; i < fbdev->num_fbs; i++) {
+		struct device *dev = dev_of_fbinfo(fbdev->fbs[i]);
+
+		if (!dev)
+			continue;
+
 		for (t = 0; t < ARRAY_SIZE(omapfb_attrs); t++)
-			device_remove_file(fbdev->fbs[i]->dev,
-					&omapfb_attrs[t]);
+			device_remove_file(dev, &omapfb_attrs[t]);
 	}
 }
 
-- 
2.43.0

[PATCH v2 4/4] fbdev: sh_mobile_lcdc: Make FB_DEVICE dependency optional

[Chintan Patel]

The sh_mobile_lcdc driver exposes overlay configuration via sysfs, but the
core driver does not require CONFIG_FB_DEVICE.

Make sysfs support optional by defining overlay_sysfs_groups as NULL when
FB_DEVICE is disabled. The driver always sets .dev_groups, and the kernel
naturally skips NULL attribute groups while the code remains buildable
and type-checked.

v2:
- Replace CONFIG_FB_DEVICE ifdefs with NULL overlay_sysfs_groups
- Always populate .dev_groups

Suggested-by: Helge Deller <deller@gmx.de>
Signed-off-by: Chintan Patel <chintanlike@gmail.com>
---
 drivers/video/fbdev/sh_mobile_lcdcfb.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/video/fbdev/sh_mobile_lcdcfb.c b/drivers/video/fbdev/sh_mobile_lcdcfb.c
index dd950e4ab5ce..704c17ad241e 100644
--- a/drivers/video/fbdev/sh_mobile_lcdcfb.c
+++ b/drivers/video/fbdev/sh_mobile_lcdcfb.c
@@ -1350,7 +1350,16 @@ static struct attribute *overlay_sysfs_attrs[] = {
 	&dev_attr_overlay_rop3.attr,
 	NULL,
 };
+
+#ifdef CONFIG_FB_DEVICE
 ATTRIBUTE_GROUPS(overlay_sysfs);
+#else
+/*
+ * When CONFIG_FB_DEVICE is disabled, define overlay_sysfs_groups as NULL.
+ * The compiler will optimize out the sysfs code paths when dev_groups is NULL.
+ */
+static const struct attribute_group *overlay_sysfs_groups[] = { NULL };
+#endif
 
 static const struct fb_fix_screeninfo sh_mobile_lcdc_overlay_fix  = {
 	.id =		"SH Mobile LCDC",
-- 
2.43.0

Re: [PATCH v2 4/4] fbdev: sh_mobile_lcdc: Make FB_DEVICE dependency optional

[Andy Shevchenko]

On Fri, Dec 19, 2025 at 7:43 AM Chintan Patel <chintanlike@gmail.com> wrote:
>
> The sh_mobile_lcdc driver exposes overlay configuration via sysfs, but the
> core driver does not require CONFIG_FB_DEVICE.
>
> Make sysfs support optional by defining overlay_sysfs_groups as NULL when
> FB_DEVICE is disabled. The driver always sets .dev_groups, and the kernel
> naturally skips NULL attribute groups while the code remains buildable
> and type-checked.

> v2:
> - Replace CONFIG_FB_DEVICE ifdefs with NULL overlay_sysfs_groups
> - Always populate .dev_groups

Same comment about the changelog in the commit messages.

...

> +#ifdef CONFIG_FB_DEVICE
>  ATTRIBUTE_GROUPS(overlay_sysfs);
> +#else
> +/*
> + * When CONFIG_FB_DEVICE is disabled, define overlay_sysfs_groups as NULL.
> + * The compiler will optimize out the sysfs code paths when dev_groups is NULL.
> + */
> +static const struct attribute_group *overlay_sysfs_groups[] = { NULL };
> +#endif

Hmm... I'm wondering if PTR_IF() can anyhow help here.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 0/4] fbdev: Make CONFIG_FB_DEVICE optional for drivers

[Andy Shevchenko]

On Fri, Dec 19, 2025 at 7:43 AM Chintan Patel <chintanlike@gmail.com> wrote:
>
> This series makes CONFIG_FB_DEVICE optional for fbdev drivers that use
> it only for sysfs interfaces, addressing Thomas Zimmermann’s TODO to
> remove hard FB_DEVICE dependencies.
>
> The series introduces a small helper, dev_of_fbinfo(), which returns
> NULL when CONFIG_FB_DEVICE=n. This allows sysfs code paths to be skipped
> via runtime checks, avoids #ifdef CONFIG_FB_DEVICE clutter, and keeps
> full compile-time syntax checking.

Please, address my comments and I give a tag for v3. I pretty much
like the series, thanks!

-- 
With Best Regards,
Andy Shevchenko