linux-kernel - RE: [PATCH v7 1/6] dt-bindings: mailbox: allow mbox-cells to be equal to 0

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Message-ID: <AM0PR04MB4211F722024F7F183774D592802B0@AM0PR04MB4211.eurprd04.prod.outlook.com>
Date:   Thu, 26 Jul 2018 11:55:04 +0000
From:   "A.s. Dong" <aisheng.dong@....com>
To:     Jassi Brar <jassisinghbrar@...il.com>
CC:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Devicetree List <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ", Sascha Hauer" <kernel@...gutronix.de>,
        ", linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, srv_heupstream" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH v7 1/6] dt-bindings: mailbox: allow mbox-cells to be equal
 to 0

> -----Original Message-----
> From: Jassi Brar [mailto:jassisinghbrar@...il.com]
> Sent: Thursday, July 26, 2018 7:37 PM
> To: A.s. Dong <aisheng.dong@....com>
> Cc: Oleksij Rempel <o.rempel@...gutronix.de>; Shawn Guo
> <shawnguo@...nel.org>; Fabio Estevam <fabio.estevam@....com>; Rob
> Herring <robh+dt@...nel.org>; Mark Rutland <mark.rutland@....com>;
> Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>; Sudeep Holla
> <sudeep.holla@....com>; Devicetree List <devicetree@...r.kernel.org>;
> Linux Kernel Mailing List <linux-kernel@...r.kernel.org>; , Sascha Hauer
> <kernel@...gutronix.de>; , linux-arm-kernel@...ts.infradead.org, linux-
> mediatek@...ts.infradead.org, srv_heupstream <linux-arm-
> kernel@...ts.infradead.org>; dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH v7 1/6] dt-bindings: mailbox: allow mbox-cells to be
> equal to 0
> 
> On Thu, Jul 26, 2018 at 4:30 PM, A.s. Dong <aisheng.dong@....com> wrote:
> >> -----Original Message-----
> >> From: Jassi Brar [mailto:jassisinghbrar@...il.com]
> >> Sent: Thursday, July 26, 2018 5:42 PM
> >> To: Oleksij Rempel <o.rempel@...gutronix.de>
> >> Cc: Shawn Guo <shawnguo@...nel.org>; Fabio Estevam
> >> <fabio.estevam@....com>; Rob Herring <robh+dt@...nel.org>; Mark
> >> Rutland <mark.rutland@....com>; A.s. Dong <aisheng.dong@....com>;
> >> Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>; Sudeep Holla
> >> <sudeep.holla@....com>; Devicetree List <devicetree@...r.kernel.org>;
> >> Linux Kernel Mailing List <linux-kernel@...r.kernel.org>; , Sascha
> >> Hauer <kernel@...gutronix.de>; ,
> >> linux-arm-kernel@...ts.infradead.org, linux-
> >> mediatek@...ts.infradead.org, srv_heupstream <linux-arm-
> >> kernel@...ts.infradead.org>; dl-linux-imx <linux-imx@....com>
> >> Subject: Re: [PATCH v7 1/6] dt-bindings: mailbox: allow mbox-cells to
> >> be equal to 0
> >>
> >> On Thu, Jul 26, 2018 at 12:23 PM, Oleksij Rempel
> >> <o.rempel@...gutronix.de>
> >> wrote:
> >> > From: Dong Aisheng <aisheng.dong@....com>
> >> >
> >> > Mailbox devices may have only one channel which means the
> >> > mbox-cells at least 1 does not make sense for this type devices.
> >> > Let's remove that limitation to allow the mbox-cells to be equal to 0.
> >> >
> >> OK
> >>
> >> But please realise that you'll have to write more code -- implement
> >> your own
> >> of_xlate() callback.
> >> Most developers would prefer to call the only channel as channel
> >> number 0, and use the common of_xlate implementation.
> >>
> >
> > Yes, that's true because the common of_xlate assuming the mbox-cells is 1.
> > And there's already such users:
> > arch/arm/boot/dts/bcm283x.dtsi
> >
> You mean that is a good thing, right?

No, I mean there's similar HW in kernel already that only has one channel.
Are you suggesting even for one channel mailbox, we should still use
Mbox-cells 1 and use 'mboxes = <&mailbox 0>' in devicetree?

Regards
Dong Aisheng