(+ Jose (SMCCC Spec author)) On Fri, May 22, 2020 at 04:46:12PM +0200, Arnd Bergmann wrote: > On Fri, May 22, 2020 at 2:50 PM Sudeep Holla <sudeep.ho...@arm.com> wrote: > > + > > + soc_id_rev = res.a0; > > + > > + soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL); > > + if (!soc_dev_attr) > > + return -ENOMEM; > > + > > + sprintf(soc_id_str, "0x%04x", IMP_DEF_SOC_ID(soc_id_version)); > > + sprintf(soc_id_rev_str, "0x%08x", soc_id_rev); > > + sprintf(soc_id_jep106_id_str, "0x%02x%02x", > > + JEP106_BANK_CONT_CODE(soc_id_version), > > + JEP106_ID_CODE(soc_id_version)); > > + > > + soc_dev_attr->soc_id = soc_id_str; > > + soc_dev_attr->revision = soc_id_rev_str; > > + soc_dev_attr->jep106_id = soc_id_jep106_id_str; > > Ok, let me try to understand how this maps the 64-bit ID into the > six strings in user space: > > For a chip that identifies as > > JEP106_BANK_CONT_CODE = 12 > JEP106_ID_CODE = 34 > IMP_DEF_SOC_ID = 5678 > soc_id_rev = 9abcdef0 > > the normal sysfs attributes contain these strings: > > machine = "" > family = "" > revision = "0x9abcdef0 > serial_number = "" > soc_id = "0x5678" > > and the new attribute is > > jep106_identification_code = "0x1234" > > This still looks like a rather poorly designed interface to me, with a > number of downsides: > > - Nothing in those strings identifies the numbers as using jep106 > numbers rather than some something else that might use strings > with hexadecimal numbers. >
Not sure if I understand your concerns completely here. Anyways I wanted to clarify that the jep106 encoding is applicable only for manufacturer's id and not for SoC ID or revision. Not sure if that changes anything about your concerns. > - I think we should have something unique in "family" just because > existing scripts can use that as the primary indentifier > I agree with your idea of combining attributes, not sure exactly which ones yet. > - It seems odd that there is no way to read the serial number through > the same interface and publish it the usual way. Valid concern and I will pass this to interface authors. > Francois Ozog > recently asked for a generic way to find out a serial number for > inventory management, and this would be the obvious place to have it. Agreed, but not sure what author(s) have to say. I have cc-ed one of them. > It can of course be added later when the next revision of the spec > is there, it just seems like a surprising omission. > Yes, definitely. Good to get feedback. > How about making the contents: > > machine = "" /* could be a future addition, but board specific */ > family = "jep106:1234" But this just indicates manufacturer id and nothing related to SoC family. If it is jep106:043b, all it indicates is Arm Ltd and assigning it to family doesn't sound right to me. I had requests for both of the above during the design of interface but I was told vendors were happy with the interface. I will let the authors speak about that. > revision = "0x9abcdef0 > serial_number = "0xfedcba987654321" /* to be implemented later */ Sure. > soc_id = "jep106:1234:5678" /* duplicates family but makes it unique*/ Not sure again. > > That would work without any new properties, dropping the other patch, > and be easier to use for identification from user space. > OK, I agree on ease part. But for me, we don't have any property in the list to indicate the vendor/manufacturer's name. I don't see issue adding one, name can be fixed as jep106_identification_code is too specific. How about manufacturer with the value in the format "jep106:1234" if it is not normal string but jep106 encoding. -- Regards, Sudeep
