Re: [PATCH] PCI: mediatek: Fix operator precedence in PCIE_FTS_NUM_L0 macro

["Krzysztof Wilczyński" <kwilczynski@kernel.org>]

Hello,

> The original PCIE_FTS_NUM_L0(x) macro was buggy due to improper operator
> precedence, where ((x) & 0xff << 8) was evaluated as ((x) & 0xff00).
> 
> Instead of just fixing the parentheses, use the standard FIELD_PREP()
> macro. This makes the code more robust by automatically handling masks
> and shifts, while also adding compile-time type and range checking to
> ensure the value fits within PCIE_FTS_NUM_MASK.
> 
> Fixes: 637cfacae96f ("PCI: mediatek: Add MediaTek PCIe host controller support")
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> ---
>  drivers/pci/controller/pcie-mediatek.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
> index 7572252..00f0e29 100644
> --- a/drivers/pci/controller/pcie-mediatek.c
> +++ b/drivers/pci/controller/pcie-mediatek.c
> @@ -61,7 +61,7 @@
>  /* MediaTek specific configuration registers */
>  #define PCIE_FTS_NUM		0x70c
>  #define PCIE_FTS_NUM_MASK	GENMASK(15, 8)
> -#define PCIE_FTS_NUM_L0(x)	((x) & 0xff << 8)
> +#define PCIE_FTS_NUM_L0(x)	FIELD_PREP(PCIE_FTS_NUM_MASK, x)

Aww.  Nice catch!  Thank you for fixing this!

Happy to offer:

  Reviewed-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

All the best,

	Krzysztof