Re: [PATCH v2] staging: sm750fb: fix unused tmp in sw_i2c_wait

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Jan 05, 2026 at 03:49:17PM +0800, Sun Jian wrote:
> clang W=1 warns that 'tmp' is set but not used in sw_i2c_wait().
> 
> sw_i2c_wait() provides the delay between bit-banged I2C GPIO transitions.
> Replace the loop-count delay with a time-based udelay(1) to avoid CPU-
> dependent timing and fix the warning.

Why is udelay(1) the same here?

> Compile-tested with clang W=1; no hardware available to validate timing.

That's going to prevent us from being able to take this, sorry :(


> 
> Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
> ---
> v2:
> - Replace cpu_relax() delay loop with time-based udelay(1) to avoid
>   CPU-dependent timing (per Greg's feedback).
> 
> v1:
> - Used cpu_relax() in the loop to silence -Wunused-but-set-variable.
> ---
>  drivers/staging/sm750fb/ddk750_swi2c.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/staging/sm750fb/ddk750_swi2c.c b/drivers/staging/sm750fb/ddk750_swi2c.c
> index 0ef8d4ff2ef9..d5843fa69bfa 100644
> --- a/drivers/staging/sm750fb/ddk750_swi2c.c
> +++ b/drivers/staging/sm750fb/ddk750_swi2c.c
> @@ -11,6 +11,7 @@
>  #include "ddk750_reg.h"
>  #include "ddk750_swi2c.h"
>  #include "ddk750_power.h"
> +#include <linux/delay.h>

Shouldn't this be at the top of the include lines?

>  
>  /*
>   * I2C Software Master Driver:
> @@ -92,12 +93,7 @@ static void sw_i2c_wait(void)
>       * it's more reliable than counter loop ..
>       * write 0x61 to 0x3ce and read from 0x3cf
>       */
> -	int i, tmp;
> -
> -	for (i = 0; i < 600; i++) {
> -		tmp = i;
> -		tmp += i;
> -	}
> +	udelay(1);

You are ignoring the comments in this function.

Also, if you reduce this to a single call, shouldn't this whole function
be removed?

thanks,

greg k-h