From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kumar Gala Subject: Re: [PATCH 1/2] Documentation: devicetree: root node serial-number property documentation Date: Thu, 16 Apr 2015 13:54:25 -0500 Message-ID: References: <1427564371-26039-1-git-send-email-contact@paulk.fr> <1429175421.2483.1.camel@collins> <1429199145.2563.9.camel@collins> <1429208077.2563.14.camel@collins> Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1429208077.2563.14.camel@collins> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Paul Kocialkowski Cc: Mark Rutland , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Russell King , Pawel Moll , Ian Campbell , Stefan Agner , Hans De Goede , Rob Herring , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: devicetree@vger.kernel.org > On Apr 16, 2015, at 1:14 PM, Paul Kocialkowski wro= te: >=20 > Le jeudi 16 avril 2015 =C3=A0 10:53 -0500, Kumar Gala a =C3=A9crit : >>> On Apr 16, 2015, at 10:45 AM, Paul Kocialkowski = wrote: >>>=20 >>> Le jeudi 16 avril 2015 =C3=A0 10:23 -0500, Kumar Gala a =C3=A9crit = : >>>>> On Apr 16, 2015, at 9:36 AM, Rob Herring = wrote: >>>>>=20 >>>>> On Thu, Apr 16, 2015 at 4:10 AM, Paul Kocialkowski wrote: >>>>>> Le jeudi 16 avril 2015 =C3=A0 09:56 +0200, Stefan Agner a =C3=A9= crit : >>>>>>> On 2015-03-28 18:39, Paul Kocialkowski wrote: >>>>>>>> Signed-off-by: Paul Kocialkowski >>>>>>>=20 >>>>>>> I think this is a worthwhile standardization. >>>>>>>=20 >>>>>>> Acked-by: Stefan Agner >>>>>>=20 >>>>>> Thanks! I should also add a commit message in v2 mentioning that= this is >>>>>> already used in open firmware and reported by lshw. >>>>>=20 >>>>> With that, >>>>>=20 >>>>> Acked-by: Rob Herring >>>=20 >>> [snip] >>>=20 >>>> I feel like this is a little lite either in the doc or commit mess= age. >>>> Is the string completely arbitrary? Is it meant to match labeling= on >>>> a board or case? Is this meant to be used by the kernel at all? >>>=20 >>> I guess it doesn't really matter what it is, as long as it's a stri= ng. >>> The kernel does not suggest any use for it either, it's just made >>> available to userspace through cpuinfo. >>>=20 >>> Now if there is a particular use for this in user-space, it would h= ave >>> to match some standards. For instance, it Android, ro.serialno is >>> usually a 16-bytes (plus one null byte) representation of a 64 bit >>> number. For USB, I recall it is usually a 32 bytes string (includin= g the >>> null byte), but may be extended to more. >>>=20 >>> What the string actually represents depends and some SOCs have seri= al >>> number bytes (I know that omap and sunxi have some for instance, th= at >>> are usually used) while other devices may take it from somewhere el= se. >>> In any case, it doesn't really matter and is not up to the kernel a= nyway >>> since it is just passed through from the bootloader. >>>=20 >>> Thus, I don't think it's very relevant to mention it in either the >>> documentation or the commit message. >>=20 >> So you say =E2=80=98board=E2=80=99 in the patch, since it could be S= oC specific, we >> should probably clean up the wording a bit. >=20 > It really doesn't matter where the string comes from, what it contain= s > or whether some SoCs have provisions to generate one. > I think board is one the most common words that we can use to describ= e > devices. "devices" is also fine, I could go with it if you prefer, bu= t I > don't really see what it changes. Lets go with device instead of board. >=20 >> I=E2=80=99m just saying when someone reads this 6 months or a year l= ater and >> tries to figure out what the purpose of the property is they don=E2=80= =99t >> really have enough info. Putting some examples in the commit messag= e >> of what possibly usages is I think a reasonable thing. >=20 > Okay, that would make sense. Still, the purpose of this is to pass th= e > serial number string from the bootloader to userspace. All of the > discussion about where to grab the serial from and what it should loo= k > like is not relevant to the kernel. Instead, it's up to the bootloade= r > that is in charge of generating the serial string, so the discussion > should happen there. Again, I=E2=80=99ve got no issues with the property and its purpose to = be used by user space, just saying we need to convey more of the intent= via commit message or updating the doc. - k --=20 Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora For= um, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html