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

Chintan Patel posted 4 patches 1 month, 3 weeks ago
There is a newer version of this series
[PATCH v2 2/4] staging: fbtft: Make FB_DEVICE dependency optional
Posted by Chintan Patel 1 month, 3 weeks ago 
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
Posted by Andy Shevchenko 1 month, 1 week ago 
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
Posted by Chintan Patel 1 month, 1 week ago 
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!
Re: [PATCH v2 2/4] staging: fbtft: Make FB_DEVICE dependency optional
Posted by Andy Shevchenko 1 month, 1 week ago 
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

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