linux-kernel - Re: [PATCH] mmc: core: Do not require secure trim for discard

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Date:   Thu, 17 Nov 2022 10:19:34 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Christian Löhle <CLoehle@...erstone.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>
Subject: Re: [PATCH] mmc: core: Do not require secure trim for discard

On 14/11/22 15:26, Christian Löhle wrote:
> Discard feature is independent of security features.
> The support check for all trims and discard falsely checked
> for secure trim/discard, but in the discard case this is not
> mandated by the spec.
> 

"Discard" was added after "Trim", so while MMC_TRIM_ARGS made
sense originally, that stopped with:

commit b3bf915308ca ("mmc: core: new discard feature support at eMMC v4.5")

So this could have that as a fixes tag.

Also MMC_TRIM_ARGS is a bit of a misleading name since it covers
one of the bits of MMC_DISCARD_ARG, so I suggest a second patch to
tidy things up.

Perhaps rename it and change the value to 8003 e.g.

#define MMC_TRIM_OR_DISCARD_ARGS	0x00008003

and make a wrapper for the Trim case:

static bool is_trim_arg(unsigned int arg)
{
	return (arg & MMC_TRIM_OR_DISCARD_ARGS) && arg != MMC_DISCARD_ARG;
}

> Signed-off-by: Christian Loehle <cloehle@...erstone.com>
> ---
>  drivers/mmc/core/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 95fa8fb1d45f..507005211529 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1761,7 +1761,8 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
>  		return -EOPNOTSUPP;
>  
>  	if (mmc_card_mmc(card) && (arg & MMC_TRIM_ARGS) &&
> -	    !(card->ext_csd.sec_feature_support & EXT_CSD_SEC_GB_CL_EN))
> +	    !(card->ext_csd.sec_feature_support & EXT_CSD_SEC_GB_CL_EN) &&
> +	    arg != MMC_DISCARD_ARG)
>  		return -EOPNOTSUPP;
>  
>  	if (arg == MMC_SECURE_ERASE_ARG) {