linux-kernel - Re: [PATCH v2 2/4] staging: fbtft: Make FB

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Message-ID: <CAHp75VeLF8nd-JiPFnxJ2H43ZS=oYgW4=BTZjR_GuUuj03gyRg@mail.gmail.com>
Date: Sat, 27 Dec 2025 16:19:25 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Chintan Patel <chintanlike@...il.com>
Cc: linux-fbdev@...r.kernel.org, linux-staging@...ts.linux.dev, 
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, tzimmermann@...e.de, andy@...nel.org, 
	deller@....de, gregkh@...uxfoundation.org
Subject: Re: [PATCH v2 2/4] staging: fbtft: Make FB_DEVICE dependency optional

On Fri, Dec 19, 2025 at 7:43 AM Chintan Patel <chintanlike@...il.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@...e.de>
> Suggested-by: Helge Deller <deller@....de>
> Signed-off-by: Chintan Patel <chintanlike@...il.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