On 2015-04-16 22:06, Paul Kocialkowski wrote: > Le jeudi 16 avril 2015 à 21:40 +0200, Stefan Agner a écrit : >> On 2015-04-16 20:14, Paul Kocialkowski wrote: >> > Le jeudi 16 avril 2015 à 10:53 -0500, Kumar Gala a écrit : >> >> > On Apr 16, 2015, at 10:45 AM, Paul Kocialkowski <contact@xxxxxxxx> wrote: >> >> > >> >> > Le jeudi 16 avril 2015 à 10:23 -0500, Kumar Gala a écrit : >> >> >>> On Apr 16, 2015, at 9:36 AM, Rob Herring <robherring2@xxxxxxxxx> wrote: >> >> >>> >> >> >>> On Thu, Apr 16, 2015 at 4:10 AM, Paul Kocialkowski <contact@xxxxxxxx> wrote: >> >> >>>> Le jeudi 16 avril 2015 à 09:56 +0200, Stefan Agner a écrit : >> >> >>>>> On 2015-03-28 18:39, Paul Kocialkowski wrote: >> >> >>>>>> Signed-off-by: Paul Kocialkowski <contact@xxxxxxxx> >> >> >>>>> >> >> >>>>> I think this is a worthwhile standardization. >> >> >>>>> >> >> >>>>> Acked-by: Stefan Agner <stefan@xxxxxxxx> >> >> >>>> >> >> >>>> Thanks! I should also add a commit message in v2 mentioning that this is >> >> >>>> already used in open firmware and reported by lshw. >> >> >>> >> >> >>> With that, >> >> >>> >> >> >>> Acked-by: Rob Herring <robh@xxxxxxxxxx> >> >> > >> >> > [snip] >> >> > >> >> >> I feel like this is a little lite either in the doc or commit message. >> >> >> 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? >> >> > >> >> > I guess it doesn't really matter what it is, as long as it's a string. >> >> > The kernel does not suggest any use for it either, it's just made >> >> > available to userspace through cpuinfo. >> >> > >> >> > Now if there is a particular use for this in user-space, it would have >> >> > 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 (including the >> >> > null byte), but may be extended to more. >> >> > >> >> > What the string actually represents depends and some SOCs have serial >> >> > number bytes (I know that omap and sunxi have some for instance, that >> >> > are usually used) while other devices may take it from somewhere else. >> >> > In any case, it doesn't really matter and is not up to the kernel anyway >> >> > since it is just passed through from the bootloader. >> >> > >> >> > Thus, I don't think it's very relevant to mention it in either the >> >> > documentation or the commit message. >> >> >> >> So you say ‘board’ in the patch, since it could be SoC specific, we >> >> should probably clean up the wording a bit. >> > >> > It really doesn't matter where the string comes from, what it contains >> > or whether some SoCs have provisions to generate one. >> > I think board is one the most common words that we can use to describe >> > devices. "devices" is also fine, I could go with it if you prefer, but I >> > don't really see what it changes. >> >> There is already something related for SoC's in SoC bus called soc_id, >> see >> Documentation/ABI/testing/sysfs-devices-soc >> >> So I would rather prefer that this is more reserved for device/board >> serial number... > > Again, I don't wish to define what the number represents in the kernel. > > It's whatever string the bootloader sends. I know that e.g. on an omap3 > device, I'll be using this with the ID bits provided by the SoC (maybe > only part of them, there are 128 bits available and I like to have 64 > bit serial numbers). But if you want your device to use something else > (e.g. some serial number stored in an external eeprom), it's up to you > to decide and in any case, that will be decided at bootloader stage. For that ID the soc_id attribute is actually much more appropriate. But if anybody wants to use that as serial-number, fine. I'm not saying we should prohibit that. > Perhaps it would make sense to provide consistency for this among a > particular family of devices (say, devices from the same manufacture or > devices using the same SoC). We have already set up such a standard for > Allwinner (sunxi) devices, in U-Boot. That is actually exactly my concern. We (Toradex) are a ARM module provider which populate SoC's of different vendors. However, we would like to keep consistency across modules. If a SoC vendor mandates to use the field for the SoC serial number, we end up with different serial numbers in that field. IMHO, the top level serial-number should be used for the board/device. But if you don't like to define that, it is ok for me. But maybe we could just mention soc_id as a possible alternative for SoC serial numbers in the documentation? -- Stefan -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
