spi: aspeed: Replace VLA parameter with flat pointer in calibration helper

[PATCH] spi: aspeed: Replace VLA parameter with flat pointer in calibration helper

Posted by Chin-Ting Kuo 6 days, 19 hours ago

aspeed_spi_ast2600_optimized_timing() declared its buffer argument as a
variable-length array parameter (u8 buf[rows][cols]), which causes a
sparse warning. Replace the VLA parameter with a plain u8 * and compute
the 2-D index manually. The corresponding call site is also updated.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202605180441.uD3toFRJ-lkp@intel.com/
Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
---
 drivers/spi/spi-aspeed-smc.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-aspeed-smc.c b/drivers/spi/spi-aspeed-smc.c
index 808659a1f460..c5275700de3d 100644
--- a/drivers/spi/spi-aspeed-smc.c
+++ b/drivers/spi/spi-aspeed-smc.c
@@ -1467,8 +1467,7 @@ static int aspeed_spi_do_calibration(struct aspeed_spi_chip *chip)
  * must contains the highest number of consecutive "pass"
  * results and not span across multiple rows.
  */
-static u32 aspeed_spi_ast2600_optimized_timing(u32 rows, u32 cols,
-					       u8 buf[rows][cols])
+static u32 aspeed_spi_ast2600_optimized_timing(u32 rows, u32 cols, u8 *buf)
 {
 	int r = 0, c = 0;
 	int max = 0;
@@ -1478,7 +1477,7 @@ static u32 aspeed_spi_ast2600_optimized_timing(u32 rows, u32 cols,
 		for (j = 0; j < cols;) {
 			int k = j;
 
-			while (k < cols && buf[i][k])
+			while (k < cols && buf[i * cols + k])
 				k++;
 
 			if (k - j > max) {
@@ -1541,7 +1540,7 @@ static int aspeed_spi_ast2600_calibrate(struct aspeed_spi_chip *chip, u32 hdiv,
 		}
 	}
 
-	calib_point = aspeed_spi_ast2600_optimized_timing(6, 17, calib_res);
+	calib_point = aspeed_spi_ast2600_optimized_timing(6, 17, &calib_res[0][0]);
 	/* No good setting for this frequency */
 	if (calib_point == 0)
 		return -1;
-- 
2.34.1

Re: [PATCH] spi: aspeed: Replace VLA parameter with flat pointer in calibration helper

Posted by Mark Brown 5 days, 18 hours ago

On Mon, May 18, 2026 at 05:57:08PM +0800, Chin-Ting Kuo wrote:

> -			while (k < cols && buf[i][k])
> +			while (k < cols && buf[i * cols + k])

This really needs () to make it clear what's going on; the precedence is
well defined but not everyone is going to know that off the top of their
head.

Re: [PATCH] spi: aspeed: Replace VLA parameter with flat pointer in calibration helper

Posted by David Laight 5 days, 11 hours ago

On Tue, 19 May 2026 12:03:51 +0100
Mark Brown <broonie@kernel.org> wrote:

> On Mon, May 18, 2026 at 05:57:08PM +0800, Chin-Ting Kuo wrote:
> 
> > -			while (k < cols && buf[i][k])
> > +			while (k < cols && buf[i * cols + k])  
> 
> This really needs () to make it clear what's going on; the precedence is
> well defined but not everyone is going to know that off the top of their
> head.

Come on, it's multiply and add - everyone is going to get that right.

-- David

Re: [PATCH] spi: aspeed: Replace VLA parameter with flat pointer in calibration helper

Posted by Mark Brown 4 days, 19 hours ago

On Tue, May 19, 2026 at 06:13:48PM +0100, David Laight wrote:
> Mark Brown <broonie@kernel.org> wrote:
> > On Mon, May 18, 2026 at 05:57:08PM +0800, Chin-Ting Kuo wrote:

> > > -			while (k < cols && buf[i][k])
> > > +			while (k < cols && buf[i * cols + k])  

> > This really needs () to make it clear what's going on; the precedence is
> > well defined but not everyone is going to know that off the top of their
> > head.

> Come on, it's multiply and add - everyone is going to get that right.

No, I have to stop and think.  It's not just "what is the rule" it's
also "is that the same rule whoever wrote the code thought there was" -
implicit precedence is the sort of thing that flags up as an alarm bell
when scanning through code.

Re: [PATCH] spi: aspeed: Replace VLA parameter with flat pointer in calibration helper

Posted by Cédric Le Goater 5 days, 23 hours ago

On 5/18/26 11:57, Chin-Ting Kuo wrote:
> aspeed_spi_ast2600_optimized_timing() declared its buffer argument as a
> variable-length array parameter (u8 buf[rows][cols]), which causes a
> sparse warning. Replace the VLA parameter with a plain u8 * and compute
> the 2-D index manually. The corresponding call site is also updated.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202605180441.uD3toFRJ-lkp@intel.com/
> Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
> ---
>   drivers/spi/spi-aspeed-smc.c | 7 +++----
>   1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/spi/spi-aspeed-smc.c b/drivers/spi/spi-aspeed-smc.c
> index 808659a1f460..c5275700de3d 100644
> --- a/drivers/spi/spi-aspeed-smc.c
> +++ b/drivers/spi/spi-aspeed-smc.c
> @@ -1467,8 +1467,7 @@ static int aspeed_spi_do_calibration(struct aspeed_spi_chip *chip)
>    * must contains the highest number of consecutive "pass"
>    * results and not span across multiple rows.
>    */
> -static u32 aspeed_spi_ast2600_optimized_timing(u32 rows, u32 cols,
> -					       u8 buf[rows][cols])
> +static u32 aspeed_spi_ast2600_optimized_timing(u32 rows, u32 cols, u8 *buf)
>   {
>   	int r = 0, c = 0;
>   	int max = 0;
> @@ -1478,7 +1477,7 @@ static u32 aspeed_spi_ast2600_optimized_timing(u32 rows, u32 cols,
>   		for (j = 0; j < cols;) {
>   			int k = j;
>   
> -			while (k < cols && buf[i][k])
> +			while (k < cols && buf[i * cols + k])
>   				k++;
>   
>   			if (k - j > max) {
> @@ -1541,7 +1540,7 @@ static int aspeed_spi_ast2600_calibrate(struct aspeed_spi_chip *chip, u32 hdiv,
>   		}
>   	}
>   
> -	calib_point = aspeed_spi_ast2600_optimized_timing(6, 17, calib_res);
> +	calib_point = aspeed_spi_ast2600_optimized_timing(6, 17, &calib_res[0][0]);
>   	/* No good setting for this frequency */
>   	if (calib_point == 0)
>   		return -1;



Reviewed-by: Cédric Le Goater <clg@kaod.org>

Thanks,

C.