begin adding phy package

phy/phy.go

@@ -0,0 +1,93 @@
+// Package phy provides Ethernet PHY management via MDIO.
+// It supports IEEE 802.3 Clause 22 and Clause 45 register access
+// for configuring and monitoring physical layer transceivers.
+package phy
+
+import (
+	"errors"
+	"time"
+)
+
+// FindPHYs finds all regular non-clause45 PHYs on the MDIO bus and writes them to dst.
+func FindPHYs(mdio MDIOBus, dst []uint8) (n int, err error) {
+	const maxAddr = 31
+	const regBasicStatus = 0x01
+	if len(dst) < 32 {
+		return -1, errors.New("require buffer length 32 for FindPHYs")
+	}
+	n = 0
+	for addr := uint8(0); addr <= maxAddr; addr++ {
+		// Future proofing for supported clause 45.
+		// Check PMA/PMD device (DEVAD 1), register 0 (control)
+		const devAddr = 1
+		var val uint16
+		val, err = mdio.Read(addr, devAddr, BMCRAddr)
+		if err != nil {
+			continue
+		}
+		// Basic status has some bits that must be zero and one, so if this check fails then we know its a bad address.
+		if val != 0xffff && val != 0x0000 {
+			dst[n] = addr
+			n++
+		}
+		time.Sleep(150 * time.Microsecond)
+	}
+	return n, err
+}
+
+type Device struct {
+	mdio    MDIOBus
+	phyaddr uint8
+	// Is 1 for Clause 45 devices and 0 for clause 22 devices.
+	clause45 uint8
+}
+
+func (d *Device) BasicControl() (BMCR, error) {
+	ctl, err := d.rread(BMCRAddr)
+	return BMCR(ctl), err
+}
+
+func (d *Device) BasicStatus(phyaddr uint8) (BMSR, error) {
+	stat, err := d.rread(BMSRAddr)
+	return BMSR(stat), err
+}
+
+func (d *Device) ID1() (uint16, error) {
+	return d.rread(regPhyId1)
+}
+
+func (d *Device) ID2() (uint16, error) {
+	return d.rread(regPhyId2)
+}
+
+func (d *Device) Reset(phyaddr uint8) error {
+	err := d.rwrite(BMCRAddr, uint16(BMCRReset))
+	if err != nil {
+		return err
+	}
+	// Wait for reset to complete (bit self-clears).
+	// IEEE 802.3 allows up to 500ms.
+	const maxPolls = 50
+	const resetTimeout = 500 * time.Millisecond // As per standard.
+	for i := 0; i < maxPolls; i++ {
+		time.Sleep(resetTimeout / maxPolls)
+		ctl, err := d.BasicControl()
+		if err != nil {
+			continue
+		}
+		if ctl&BMCRReset == 0 {
+			return nil
+		}
+	}
+	return errors.New("PHY reset timeout")
+}
+
+// rwrite mdio register write.
+func (d *Device) rwrite(addr uint16, value uint16) error {
+	return d.mdio.Write(d.phyaddr, d.clause45, addr, value)
+}
+
+// rread mdio register read.
+func (d *Device) rread(addr uint16) (value uint16, _ error) {
+	return d.mdio.Read(d.phyaddr, d.clause45, addr)
+}