From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Horman Subject: Re: [PATCH can-next 1/2] CAN: rcar: add gen[12] fallback compatibility strings Date: Tue, 23 Feb 2016 09:08:22 +0900 Message-ID: <20160223000822.GF1853@verge.net.au> References: <1456107350-12100-1-git-send-email-horms+renesas@verge.net.au> <1456107350-12100-2-git-send-email-horms+renesas@verge.net.au> <20160222033720.GA27711@rob-hp-laptop> <56CAD795.1090509@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <56CAD795.1090509@pengutronix.de> Sender: netdev-owner@vger.kernel.org To: Marc Kleine-Budde Cc: Rob Herring , Wolfgang Grandegger , Magnus Damm , linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org On Mon, Feb 22, 2016 at 10:40:37AM +0100, Marc Kleine-Budde wrote: > On 02/22/2016 04:37 AM, Rob Herring wrote: > > On Mon, Feb 22, 2016 at 11:15:49AM +0900, Simon Horman wrote: > >> Add fallback compatibility string for R-Car Gen 1 and Gen2 families. > >> This is in keeping with the fallback scheme being adopted wherever > >> appropriate for drivers for Renesas SoCs. > >> > >> Signed-off-by: Simon Horman > >> --- > >> Documentation/devicetree/bindings/net/can/rcar_can.txt | 4 +++- > >> drivers/net/can/rcar_can.c | 2 ++ > >> 2 files changed, 5 insertions(+), 1 deletion(-) > > > > Acked-by: Rob Herring > > I'm not following the latest DT discussions, is there a (new) decision > to add such "generic" compatibles? AFAIK you add the oldest device > that's compatible with your driver to your SoC dtsi at rightmost > compatible. You can add one that identifies your SoC's IP core in front > of it. So there's no need to modify the driver until an IP core needs > different handling. > > In your case you'd identify the oldest SoC that implements the Gen1 IP > core and use this instead of "renesas,can-gen1. Same for Gen2 IP core. In the case of Renesas R-Car hardware we know that there are generations of SoCs, e.g. Gen 1 and Gen 2, but beyond that its not clear what the relationship between IP blocks might be. For example, I believe that r8a7779 is older than r8a7778 but that doesn't imply that the latter is a descendant of the former or vice versa.