From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexandre Belloni Subject: Re: [RFC PATCH 3/7] i2c: allow DT nodes without 'compatible' Date: Thu, 12 Mar 2020 12:44:32 +0100 Message-ID: <20200312114432.GA3384@piout.net> References: <20200220172403.26062-1-wsa+renesas@sang-engineering.com> <20200220172403.26062-4-wsa+renesas@sang-engineering.com> <20200312111950.GA1013@ninjato> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200312111950.GA1013@ninjato> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: Luca Ceresoli , Geert Uytterhoeven , Wolfram Sang , Linux I2C , Linux-Renesas , linux-i3c-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Kieran Bingham , Niklas =?iso-8859-1?Q?S=F6derlund?= , Jacopo Mondi , Laurent Pinchart , Vladimir Zapolskiy , Linux Kernel Mailing List , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" List-Id: linux-i2c@vger.kernel.org On 12/03/2020 12:19:51+0100, Wolfram Sang wrote: > > Clearly this does not fit the case reported by Alexandre: a device > > having a driver which is known to be badly buggy, so we don't want to > > instantiate it. But again, this should not affect DT as it is not > > describing the HW, but only an implementation detail. Probably disabling > > or blacklisting the driver would be a better option there? > > "Fixing the driver" is the first thing coming to my mind ;) But yeah, > blacklisting would be another good solution. With only the information > above, DT is not the right place to fix a broken driver. > To be clear, the driver is working properly but the HW isn't. It is a PMIC and we need to avoid linux talking to it so the PMIC doesn't end up killing the bus. We end up with a node properly described in the device tree but with status = "disabled". The relevance to the discussion was that you know what is there and you want to avoid using its address. See the pmic node on i2c1 in arch/arm/boot/dts/at91-sama5d3_xplained.dts for what I'm referring to. > > My apologies to Wolfram, I appreciate a lot the effort you are doing, > > but before reviewing this patch I have never realized what I tried to > > explain above. > > All good, Luca! Talking over code usually brings in viewpoints which > have been missed so far. This is expected. Actually, I am very happy to > have this discussion! > > All the best, > > Wolfram > -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com