Re: [PATCH net-next 2/2] net: phy: sfp: enable i2c-bus detection on ACPI based systems

On Mon, May 06, 2019 at 07:59:51AM +0300, Mika Westerberg wrote:

On Sun, May 05, 2019 at 03:05:23PM -0700, Ruslan Babayev wrote:

quoted

Lookup I2C adapter using the "i2c-bus" device property on ACPI based
systems similar to how it's done with DT.

An example DSD describing an SFP on an ACPI based system:

Device (SFP0)
{
    Name (_HID, "PRP0001")
    Name (_DSD, Package ()
    {
        ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
        Package () {
            Package () { "compatible", "sff,sfp" },
            Package () { "i2c-bus", \_SB.PCI0.RP01.I2C.MUX.CH0 },

Hmm, ACPI has I2cSerialBusV2() resource for this purpose. Why you are not
using that?

Hi Mika

Does that reference the bus as a whole, or a device on the bus?

The SFP subsystem needs a reference to the bus as a whole. There can
be an at24 like EEPROM at addresses 0x50 and 0x51. There can be an
MDIO bus encapsulated in i2c at addresses 0x40-0x5f, excluding 0x50
and 0x51. What actually is there depends on the SFP module which is
plugged into the SFP cage, and it is all hot-plugable.

	Andrew