linux-kernel - Re: [PATCH v6] staging: fbtft: Use fbdev logging helpers when FB

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Message-ID: <2026011341-chomp-protegee-6be5@gregkh>
Date: Tue, 13 Jan 2026 07:16:27 +0100
From: Greg KH <gregkh@...uxfoundation.org>
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, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v6] staging: fbtft: Use fbdev logging helpers when
 FB_DEVICE is disabled

On Mon, Jan 12, 2026 at 08:59:09PM -0800, Chintan Patel wrote:
> Replace direct accesses to info->dev with fb_dbg() and fb_info()
> helpers to avoid build failures when CONFIG_FB_DEVICE=n.

Why is there a fb_* specific logging helper?  dev_info() and dev_dbg()
should be used instead.

> Fixes: a06d03f9f238 ("staging: fbtft: Make FB_DEVICE dependency optional")

Is this really a bug?

> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202601110740.Y9XK5HtN-lkp@intel.com
> Signed-off-by: Chintan Patel <chintanlike@...il.com>
> 
> Changes in v6:
> - Switch debug/info logging to fb_dbg() and fb_info()(suggested by Thomas Zimmermann)
> - Drop dev_of_fbinfo() usage in favor of framebuffer helpers that implicitly
>   handle the debug/info context.
> - Drop __func__ usage per review feedback(suggested by greg k-h)
> - Add Fixes tag for a06d03f9f238 ("staging: fbtft: Make FB_DEVICE dependency optional")
>   (suggested by Andy Shevchenko)
> 
> Changes in v5:
> - Initial attempt to replace info->dev accesses using
>   dev_of_fbinfo() helper
> ---

The changelog stuff goes below the --- line.

>  drivers/staging/fbtft/fbtft-core.c | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c
> index 8a5ccc8ae0a1..1b3b62950205 100644
> --- a/drivers/staging/fbtft/fbtft-core.c
> +++ b/drivers/staging/fbtft/fbtft-core.c
> @@ -365,9 +365,9 @@ static int fbtft_fb_setcolreg(unsigned int regno, unsigned int red,
>  	unsigned int val;
>  	int ret = 1;
>  
> -	dev_dbg(info->dev,
> -		"%s(regno=%u, red=0x%X, green=0x%X, blue=0x%X, trans=0x%X)\n",
> -		__func__, regno, red, green, blue, transp);
> +	fb_dbg(info,
> +	       "regno=%u, red=0x%X, green=0x%X, blue=0x%X, trans=0x%X\n",
> +	       regno, red, green, blue, transp);

I dont understand what is wrong with the existing dev_dbg() line (with
the exception that __func__ should not be in it.

>  
>  	switch (info->fix.visual) {
>  	case FB_VISUAL_TRUECOLOR:
> @@ -391,8 +391,7 @@ static int fbtft_fb_blank(int blank, struct fb_info *info)
>  	struct fbtft_par *par = info->par;
>  	int ret = -EINVAL;
>  
> -	dev_dbg(info->dev, "%s(blank=%d)\n",
> -		__func__, blank);
> +	fb_dbg(info, "blank=%d\n", blank);

Same here, what's wrong with dev_dbg()?


>  
>  	if (!par->fbtftops.blank)
>  		return ret;
> @@ -793,11 +792,11 @@ int fbtft_register_framebuffer(struct fb_info *fb_info)
>  	if (spi)
>  		sprintf(text2, ", spi%d.%d at %d MHz", spi->controller->bus_num,
>  			spi_get_chipselect(spi, 0), spi->max_speed_hz / 1000000);
> -	dev_info(fb_info->dev,
> -		 "%s frame buffer, %dx%d, %d KiB video memory%s, fps=%lu%s\n",
> -		 fb_info->fix.id, fb_info->var.xres, fb_info->var.yres,
> -		 fb_info->fix.smem_len >> 10, text1,
> -		 HZ / fb_info->fbdefio->delay, text2);
> +	fb_info(fb_info,
> +		"%s frame buffer, %dx%d, %d KiB video memory%s, fps=%lu%s\n",
> +		fb_info->fix.id, fb_info->var.xres, fb_info->var.yres,
> +		fb_info->fix.smem_len >> 10, text1,
> +		HZ / fb_info->fbdefio->delay, text2);

When drivers work properly, they are quiet.  Why is this needed at all
except as a debug message?

thanks,

greg k-h