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

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Date: Tue, 23 Jan 2024 13:53:46 +0000
From: Mark Brown <broonie@...nel.org>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Herve Codina <herve.codina@...tlin.com>,
	Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>,
	Guenter Roeck <linux@...ck-us.net>,
	"linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH] spi: Raise limit on number of chip selects

On Tue, Jan 23, 2024 at 01:26:04PM +0000, Christophe Leroy wrote:
> Le 23/01/2024 à 14:18, Mark Brown a écrit :
> > On Tue, Jan 23, 2024 at 12:04:30PM +0100, Herve Codina wrote:

> >> Moving the SPI_CS_CNT_MAX value from 4 to 8 is not enough to handle my case.
> >> Tested moving SPI_CS_CNT_MAX to 16 and it was ok.

> > OK, I've also heard 12 as a number which this would cover.

> By the way the comment in include/linux/spi/spi.h is confusing. This 
> SPI_CS_CNT_MAX is really not the max number of CS supported per SPI 
> device but the max number of CS supported per SPI controller.

Well, it's a combination of the comment being confusing and the
implementation being a bit broken - we simply shouldn't be limiting the
number of chip selects per controller, the per device limit is much more
reasonable.  So ideally the code would be changed to reflect the
comment.

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