From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Shyti Subject: Re: [PATCH 1/5] spi: do not fail if the CS line is not connected Date: Sun, 19 Jun 2016 15:09:02 +0900 Message-ID: <20160619060902.GB424@jack.zhora.eu> References: <1466150245-2648-1-git-send-email-andi.shyti@samsung.com> <1466150245-2648-2-git-send-email-andi.shyti@samsung.com> <20160617104725.GC26099@sirena.org.uk> <20160617113622.GA10760@jack.zhora.eu> <20160617122803.GN26099@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andi Shyti , Andi Shyti , Kukjin Kim , Krzysztof Kozlowski , linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org To: Mark Brown Return-path: Content-Disposition: inline In-Reply-To: <20160617122803.GN26099-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Hi Mark, > > > > In this case do not fail and defer to the SPI device drivers the > > > > responsibility to check whether the num-cs is '0'. > > > > A SPI controller always has one chip seelct, it may not be controllable > > > but it's at least logically present. > > > This is true, but there are cases where the CS is not connected > > and this case needs to be treated separately to allow the device > > to work. > > In what way? It is just as easy for a device with no physical chip > select to have a logical chip select of 0 that it does nothing with as > it is for that device to handle any other number. That is indeed my case: the s3c64xx doesn't send anything, unless I manually enable CS (from the next patches I need to write '0' in the CS register). But I need smoething to tell to the device that the CS line is not connected, for example a flag in the DTS. It comes natural to me to set "num-cs = <0>" instead of defining a new property. In this case I will consider that there is no CS line, even though there is a CS controller. Thanks, Andi -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html