linux-kernel - Re: [PATCH v2 1/2] spi: spi-mem: Protect dirmap_create() with spi_mem_access

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Message-ID: <ccb6b5b3-84cd-4197-a770-7e626c1ddcf3@molgen.mpg.de>
Date: Sun, 18 Jan 2026 00:46:57 +0100
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Chin-Ting Kuo <chin-ting_kuo@...eedtech.com>
Cc: clg@...d.org, broonie@...nel.org, boris.brezillon@...tlin.com,
 joel@....id.au, andrew@...econstruct.com.au, linux-aspeed@...ts.ozlabs.org,
 openbmc@...ts.ozlabs.org, linux-spi@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 BMC-SW@...eedtech.com
Subject: Re: [PATCH v2 1/2] spi: spi-mem: Protect dirmap_create() with
 spi_mem_access_start/end

Dear Chin-Ting,


Thank you for your patch.

Am 17.01.26 um 14:42 schrieb Chin-Ting Kuo:
> spi_mem_dirmap_create() may reconfigure controller-wide settings,
> which can interfere with concurrent transfers to other devices
> sharing the same SPI controller but using different chip selects.
> 
> Wrap the ->dirmap_create() callback with spi_mem_access_start() and
> spi_mem_access_end() to serialize access and prevent cross-CS
> interference during dirmap creation.

Do you have a reproducer for this issue to test your patch? If yes, it’d 
be great, if you documented it.

> Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@...eedtech.com>
> ---
>   drivers/spi/spi-mem.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index c8b2add2640e..85702a77b3c8 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -708,9 +708,18 @@ spi_mem_dirmap_create(struct spi_mem *mem,
>   
>   	desc->mem = mem;
>   	desc->info = *info;
> -	if (ctlr->mem_ops && ctlr->mem_ops->dirmap_create)
> +	if (ctlr->mem_ops && ctlr->mem_ops->dirmap_create) {
> +		ret = spi_mem_access_start(mem);
> +		if (ret) {
> +			kfree(desc);
> +			return ERR_PTR(ret);
> +		}
> +
>   		ret = ctlr->mem_ops->dirmap_create(desc);
>   
> +		spi_mem_access_end(mem);
> +	}
> +
>   	if (ret) {
>   		desc->nodirmap = true;
>   		if (!spi_mem_supports_op(desc->mem, &desc->info.op_tmpl))

Reviewed-by: Paul Menzel <pmenzel@...gen.mpg.de>


Kind regards,

Paul