linux-kernel - Re: [PATCH v2] spi: Raise limit on number of chip selects

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Message-ID: <20250626-practical-heavenly-pony-af7296-mkl@pengutronix.de>
Date: Thu, 26 Jun 2025 15:12:47 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Mark Brown <broonie@...nel.org>
Cc: Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>, 
	Guenter Roeck <linux@...ck-us.net>, linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org, 
	kernel@...gutronix.de
Subject: Re: [PATCH v2] spi: Raise limit on number of chip selects

(sorry my mail setup had a glitch in my previous mail)

On 24.01.2024 13:24:24, Mark Brown wrote:
> As reported by Guenter the limit we've got on the number of chip selects is
> set too low for some systems, raise the limit. We should really remove the
> hard coded limit but this is needed as a fix so let's do the simple thing
> and raise the limit for now.

We currently have a use case for 24 chip selects.

> Fixes: 4d8ff6b0991d ("spi: Add multi-cs memories support in SPI core")
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Suggested-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
> Changes in v2:
> - Raise the limit further, the highest I've seen thus far is 12.
> - Link to v1: https://lore.kernel.org/r/20240122-spi-multi-cs-max-v1-1-a7e98cd5f6c7@kernel.org
> ---
>  include/linux/spi/spi.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
> index 471fe2ff9066..600fbd5daf68 100644
> --- a/include/linux/spi/spi.h
> +++ b/include/linux/spi/spi.h
> @@ -21,7 +21,7 @@
>  #include <uapi/linux/spi/spi.h>
>  
>  /* Max no. of CS supported per spi device */
> -#define SPI_CS_CNT_MAX 4
> +#define SPI_CS_CNT_MAX 16

Just further increase the limit to 24? Add a Kconfig symbol?

regards,
Marc

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