linux-kernel - Re: [PATCH] spi: spi-fsl-lpspi: convert min

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Message-ID: <20251209192059.43d97a72@pumpkin>
Date: Tue, 9 Dec 2025 19:20:59 +0000
From: david laight <david.laight@...box.com>
To: Carlos Song <carlos.song@....com>
Cc: Frank.Li@....com, broonie@...nel.org, daniel.baluta@....com,
 andriy.shevchenko@...el.com, linux-spi@...r.kernel.org,
 imx@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spi: spi-fsl-lpspi: convert min_t() to simple min()

On Tue,  9 Dec 2025 13:56:34 +0800
Carlos Song <carlos.song@....com> wrote:

> Convert min_t() to simple min() for better readability.
> 
> Fixes: 9f0c21bac5a8 ("spi: spi-fsl-lpspi: fix watermark truncation caused by type cast")
> Signed-off-by: Carlos Song <carlos.song@....com>
> ---
>  drivers/spi/spi-fsl-lpspi.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
> index 065456aba2ae..01c674d466ed 100644
> --- a/drivers/spi/spi-fsl-lpspi.c
> +++ b/drivers/spi/spi-fsl-lpspi.c
> @@ -489,12 +489,9 @@ static int fsl_lpspi_setup_transfer(struct spi_controller *controller,
>  	/*
>  	 * t->len is 'unsigned' and txfifosize and watermrk is 'u8', force
>  	 * type cast is inevitable. When len > 255, len will be truncated in min_t(),
> -	 * it caused wrong watermark set. 'unsigned int' is as the designated type
> -	 * for min_t() to avoid truncation.
> +	 * it caused wrong watermark set. Simple min() helps to do type cast.
>  	 */

That comment doesn't make any sense and can probably be deleted.
I'm not sure its did before either.
Looks like it was added because the code was originally min_t(u8, ...),
even then I looks like text for the commit message not a code comment.

With the current version of min() no casts are required, the comparison
uses the normal integer promotion rules, so u8 => int => unsigned int.
min() allows the comparison because both variables are unsigned.

	David

> -	fsl_lpspi->watermark = min_t(unsigned int,
> -				     fsl_lpspi->txfifosize,
> -				     t->len);
> +	fsl_lpspi->watermark = min(fsl_lpspi->txfifosize, t->len);
>  
>  	if (fsl_lpspi_can_dma(controller, spi, t))
>  		fsl_lpspi->usedma = true;