Messages in this thread | | | Subject | Re: [net-next PATCH v3 4/5] net: phy: Introduce fwnode_get_phy_id() | From | Jeremy Linton <> | Date | Thu, 7 May 2020 14:54:09 -0500 |
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Hi,
On 5/7/20 12:27 PM, Andy Shevchenko wrote: > On Thu, May 7, 2020 at 4:26 PM Jeremy Linton <jeremy.linton@arm.com> wrote: >> On 5/5/20 8:29 AM, Calvin Johnson wrote: > >>> + if (sscanf(cp, "ethernet-phy-id%4x.%4x", >>> + &upper, &lower) == 2) { >>> + *phy_id = ((upper & 0xFFFF) << 16) | (lower & 0xFFFF); >>> + return 0; >>> + } > >> Isn't the ACPI _CID() conceptually similar to the DT compatible >> property? > > Where?
Not, sure I understand exactly what your asking. AFAIK, in general the dt property is used to select a device driver/etc based on a more to less compatible set of substrings. The phy case is a bit different because it codes a numerical part number into the string rather than just using arbitrary strings to select a driver and device. But it uses that as a vendor selector for binding to the correct driver/device.
Rephrasing the ACPI spec, the _CID() is either a single compatible id, or a list of ids in order of preference. Each id is either a HID (string or EISA type id) or a bus specific string encoding vendor/device/etc. (https://elixir.bootlin.com/linux/v5.7-rc4/source/drivers/acpi/acpica/utids.c#L186). One of the examples is "PCI\VEN_vvvv&DEV_dddd"
So that latter case seems to be almost exactly what we have here.
> >> It even appears to be getting used in a similar way to >> identify particular phy drivers in this case. > > _CID() is a string. It can't be used as pure number. >
It does have a numeric version defined for EISA types. OTOH I suspect that your right. If there were a "PHY\VEN_IDvvvv&ID_DDDD" definition, it may not be ideal to parse it. Instead the normal ACPI model of exactly matching the complete string in the phy driver might be more appropriate.
Similarly to how I suspect the next patch's use of "compatible" isn't ideal either, because whether a device is c45 or not, should tend to be fixed to a particular vendor/device implementation and not a firmware provided property.
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