linux-kernel - Re: [PATCH] staging: sm750fb: replace magic number with defined constant

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Message-ID: <2026012705-flannels-directive-e15b@gregkh>
Date: Tue, 27 Jan 2026 14:32:37 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Madhumitha Sundar <madhuananda18@...il.com>
Cc: sudipm.mukherjee@...il.com, teddy.wang@...iconmotion.com,
	linux-fbdev@...r.kernel.org, linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: sm750fb: replace magic number with defined
 constant

On Tue, Jan 27, 2026 at 01:27:58PM +0000, Madhumitha Sundar wrote:
> The hardware wait loop in hw_sm750_de_wait uses a hardcoded magic
> number (0x10000000) for the timeout counter.
> 
> Define a constant SM750_MAX_LOOP in sm750.h and use it to improve
> code readability and maintainability.
> 
> Signed-off-by: Madhumitha Sundar <madhuananda18@...il.com>
> ---
>  drivers/staging/sm750fb/sm750.h    | 2 ++
>  drivers/staging/sm750fb/sm750_hw.c | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/sm750fb/sm750.h b/drivers/staging/sm750fb/sm750.h
> index fcb7d586e..ae07ceec1 100644
> --- a/drivers/staging/sm750fb/sm750.h
> +++ b/drivers/staging/sm750fb/sm750.h
> @@ -12,6 +12,8 @@
>  #define SM750LE_REVISION_ID ((unsigned char)0xfe)
>  #endif
>  
> +#define SM750_MAX_LOOP 0x10000000
> +
>  enum sm750_pnltype {
>  	sm750_24TFT = 0,	/* 24bit tft */
>  	sm750_dualTFT = 2,	/* dual 18 bit tft */
> diff --git a/drivers/staging/sm750fb/sm750_hw.c b/drivers/staging/sm750fb/sm750_hw.c
> index ce46f240c..f051bd75f 100644
> --- a/drivers/staging/sm750fb/sm750_hw.c
> +++ b/drivers/staging/sm750fb/sm750_hw.c
> @@ -523,7 +523,7 @@ int hw_sm750le_de_wait(void)
>  
>  int hw_sm750_de_wait(void)
>  {
> -	int i = 0x10000000;
> +	int i = SM750_MAX_LOOP;
>  	unsigned int mask = SYSTEM_CTRL_DE_STATUS_BUSY |
>  			    SYSTEM_CTRL_DE_FIFO_EMPTY |
>  			    SYSTEM_CTRL_DE_MEM_FIFO_EMPTY;

This type of "loop delay" does not work at all.  Can you try to fix this
up to use a proper timing check instead of just relying on how fast the
CPU can process instructions?

thanks,

greg k-h