From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mitch Bradley Subject: Re: Request review of device tree documentation Date: Fri, 11 Jun 2010 18:48:21 -1000 Message-ID: <4C131195.1000009@firmworks.com> References: <33BD8E86-9397-432A-97BF-F154812C157B@digitaldans.com> <1276311487.1962.172.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1276311487.1962.172.camel@pasglop> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Benjamin Herrenschmidt Cc: microblaze-uclinux-rVRm/Wmeqae7NGdpmJTKYQ@public.gmane.org, Dan Malek , devicetree-discuss , Jeremy Kerr , linuxppc-dev List-Id: devicetree@vger.kernel.org Benjamin Herrenschmidt wrote: > On Fri, 2010-06-11 at 16:47 -0700, Dan Malek wrote: > >> Hi Grant. >> >> On Jun 11, 2010, at 3:59 PM, Grant Likely wrote: >> >> >>> I've been doing a bit of work on some introductory level documentation >>> of the flattened device tree. >>> >> Wow, I feel empowered to create device trees now :-) >> Seriously, I never understood this well and this is a >> great document. >> >> I have one source of confusion. Your first Initial structure >> example uses 'compatible' to describe the machine, the >> paragraph below then mentions the 'model' property, >> and all subsequent examples use model. >> >> Does this mean if I use just the single line in the dts, >> using 'compatible' implies the ARM machine ID? If I >> have more description I use 'model'? >> > > Normally, "compatible" is what is used for code to match, > and model is more like a user-visible thingy. > Indeed, one common use of "model" - at least in the systems I work on - is to display the name of the machine in a system identification banner that the user sees. > It's possible to peek at 'model' tho, in some cases, I've seen the case > for example where things are -supposed- to be identical from an arch > point of view, have the same compatible, but later on, a quirk is found > and a test against model is used to differentiate. But that's something > to avoid in general. Better off having multiple strings in "compatible" > then, one more "generic" to have the BSP match against, and one more > "specific" that can be used if a quirk is needed. > > Of course, it doesn't help that all pseries have "chrp" and nothing else > as compatible :-) But then, both IBM and Apple have been quite lax with > their (ab)use of the DT. > > Cheers, > Ben. > > > _______________________________________________ > devicetree-discuss mailing list > devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org > https://lists.ozlabs.org/listinfo/devicetree-discuss > > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rs35.luxsci.com (rs35.luxsci.com [66.216.127.90]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id B5013B7D8E for ; Sat, 12 Jun 2010 14:48:58 +1000 (EST) Message-ID: <4C131195.1000009@firmworks.com> Date: Fri, 11 Jun 2010 18:48:21 -1000 From: Mitch Bradley MIME-Version: 1.0 To: Benjamin Herrenschmidt Subject: Re: Request review of device tree documentation References: <33BD8E86-9397-432A-97BF-F154812C157B@digitaldans.com> <1276311487.1962.172.camel@pasglop> In-Reply-To: <1276311487.1962.172.camel@pasglop> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: microblaze-uclinux@itee.uq.edu.au, Dan Malek , devicetree-discuss , Jeremy Kerr , linuxppc-dev List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Benjamin Herrenschmidt wrote: > On Fri, 2010-06-11 at 16:47 -0700, Dan Malek wrote: > >> Hi Grant. >> >> On Jun 11, 2010, at 3:59 PM, Grant Likely wrote: >> >> >>> I've been doing a bit of work on some introductory level documentation >>> of the flattened device tree. >>> >> Wow, I feel empowered to create device trees now :-) >> Seriously, I never understood this well and this is a >> great document. >> >> I have one source of confusion. Your first Initial structure >> example uses 'compatible' to describe the machine, the >> paragraph below then mentions the 'model' property, >> and all subsequent examples use model. >> >> Does this mean if I use just the single line in the dts, >> using 'compatible' implies the ARM machine ID? If I >> have more description I use 'model'? >> > > Normally, "compatible" is what is used for code to match, > and model is more like a user-visible thingy. > Indeed, one common use of "model" - at least in the systems I work on - is to display the name of the machine in a system identification banner that the user sees. > It's possible to peek at 'model' tho, in some cases, I've seen the case > for example where things are -supposed- to be identical from an arch > point of view, have the same compatible, but later on, a quirk is found > and a test against model is used to differentiate. But that's something > to avoid in general. Better off having multiple strings in "compatible" > then, one more "generic" to have the BSP match against, and one more > "specific" that can be used if a quirk is needed. > > Of course, it doesn't help that all pseries have "chrp" and nothing else > as compatible :-) But then, both IBM and Apple have been quite lax with > their (ab)use of the DT. > > Cheers, > Ben. > > > _______________________________________________ > devicetree-discuss mailing list > devicetree-discuss@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/devicetree-discuss > >