linux-kernel - Re: [PATCH 5/8] mmc: sdhci-of-aspeed: Fix null pointer

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Message-ID: <4e6fd85cc8ed6c4261844842bc2e5e54e5db04e6.camel@codeconstruct.com.au>
Date: Wed, 18 Jun 2025 12:19:53 +0930
From: Andrew Jeffery <andrew@...econstruct.com.au>
To: Cool Lee <cool_lee@...eedtech.com>, adrian.hunter@...el.com, 
	ulf.hansson@...aro.org, joel@....id.au, p.zabel@...gutronix.de, 
	linux-aspeed@...ts.ozlabs.org, openbmc@...ts.ozlabs.org, 
	linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/8] mmc: sdhci-of-aspeed: Fix null pointer

On Sun, 2025-06-15 at 11:58 +0800, Cool Lee wrote:
> Platform data might be null.

Currently it can't be:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/mmc/host/sdhci-of-aspeed.c?h=v6.16-rc2#n375

Are there future circumstances where it may be NULL?

I'm all for reducing the reasoning from global to local, but I think
some discussion in the commit message would be good.

> 
> Signed-off-by: Cool Lee <cool_lee@...eedtech.com>
> ---
>  drivers/mmc/host/sdhci-of-aspeed.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-of-aspeed.c
> b/drivers/mmc/host/sdhci-of-aspeed.c
> index 2bdd93a3f91f..22dde915e51b 100644
> --- a/drivers/mmc/host/sdhci-of-aspeed.c
> +++ b/drivers/mmc/host/sdhci-of-aspeed.c
> @@ -241,7 +241,7 @@ static void aspeed_sdhci_set_clock(struct
> sdhci_host *host, unsigned int clock)
>         struct sdhci_pltfm_host *pltfm_host;
>         unsigned long parent, bus;
>         struct aspeed_sdhci *sdhci;
> -       int div;
> +       int div = 1;
>         u16 clk;
>  
>         pltfm_host = sdhci_priv(host);
> @@ -257,6 +257,9 @@ static void aspeed_sdhci_set_clock(struct
> sdhci_host *host, unsigned int clock)
>         if (WARN_ON(clock > host->max_clk))
>                 clock = host->max_clk;
>  
> +       if (sdhci->pdata)

Given this shouldn't be the case, perhaps precede it with a
WARN_ONCE(!sdhci->pdata)?

Andrew

> +               div = sdhci->pdata->clk_div_start;
> +
>         /*
>          * Regarding the AST2600:
>          *
> @@ -273,7 +276,7 @@ static void aspeed_sdhci_set_clock(struct
> sdhci_host *host, unsigned int clock)
>          * supporting the value 0 in (EMMC12C[7:6], EMMC12C[15:8]),
> and capture
>          * the 0-value capability in clk_div_start.
>          */
> -       for (div = sdhci->pdata->clk_div_start; div < 256; div *= 2)
> {
> +       for (; div < 256; div *= 2) {
>                 bus = parent / div;
>                 if (bus <= clock)
>                         break;