From 6fcb6211866f3ed10dbf8f471ae1722aeb7e70d9 Mon Sep 17 00:00:00 2001
From: Andrea Barisani <andrea@inversepath.com>
Date: Tue, 21 Jan 2025 09:14:06 +0100
Subject: [PATCH] tidying

---
 go.mod                     |  2 ++
 go.sum                     |  2 ++
 internal/reg/port_amd64.s  |  8 ++++----
 internal/reg/reg32_amd64.s | 12 +++++------
 kvm/virtio/descriptor.go   | 42 +++++++++++++++++++++-----------------
 soc/nxp/i2c/i2c.go         |  4 ++--
 6 files changed, 39 insertions(+), 31 deletions(-)

diff --git a/go.mod b/go.mod
index 2fca83ff..23af5369 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module github.com/usbarmory/tamago
 
 go 1.23.0
+
+require golang.org/x/sync v0.10.0
diff --git a/go.sum b/go.sum
index e69de29b..cf16d914 100644
--- a/go.sum
+++ b/go.sum
@@ -0,0 +1,2 @@
+golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
+golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
diff --git a/internal/reg/port_amd64.s b/internal/reg/port_amd64.s
index fe22229e..9d67a4b3 100644
--- a/internal/reg/port_amd64.s
+++ b/internal/reg/port_amd64.s
@@ -7,11 +7,11 @@
 // that can be found in the LICENSE file.
 
 // func In8(port uint16) (val uint8)
-TEXT ·In8(SB),$0-3
+TEXT ·In8(SB),$0-9
 	MOVW	port+0(FP), DX
 	// in al, dx
 	BYTE	$0xec
-	MOVB	AL, ret+8(FP)
+	MOVB	AL, val+8(FP)
 	RET
 
 // func Out8(port uint16, val uint8)
@@ -23,11 +23,11 @@ TEXT ·Out8(SB),$0-3
 	RET
 
 // func In32(port uint32) (val uint32)
-TEXT ·In32(SB),$0-8
+TEXT ·In32(SB),$0-12
 	MOVL	port+0(FP), DX
 	// in eax, dx
 	BYTE	$0xed
-	MOVL	AX, ret+8(FP)
+	MOVL	AX, val+8(FP)
 	RET
 
 // func Out32(port uint32, val uint32)
diff --git a/internal/reg/reg32_amd64.s b/internal/reg/reg32_amd64.s
index 9c8a2489..d6284d94 100644
--- a/internal/reg/reg32_amd64.s
+++ b/internal/reg/reg32_amd64.s
@@ -8,15 +8,15 @@
 
 // func Move(dst uint32, src uint32)
 TEXT ·Move(SB),$0-8
-	MOVW	dst+0(FP), AX
-	MOVW	src+4(FP), BX
+	MOVL	dst+0(FP), AX
+	MOVL	src+4(FP), BX
 
 	// copy src to dst
-	MOVW	(AX), CX
-	MOVW	CX, (AX)
+	MOVL	(AX), CX
+	MOVL	CX, (AX)
 
 	// zero out src
-	MOVW	$0, CX
-	MOVW	CX, (BX)
+	MOVL	$0, CX
+	MOVL	CX, (BX)
 
 	RET
diff --git a/kvm/virtio/descriptor.go b/kvm/virtio/descriptor.go
index 857d09b3..7d868d31 100644
--- a/kvm/virtio/descriptor.go
+++ b/kvm/virtio/descriptor.go
@@ -50,14 +50,6 @@ func (d *Descriptor) Bytes() []byte {
 	return buf.Bytes()
 }
 
-// SetLength updates the descriptor length field.
-func (d *Descriptor) SetLength(length uint32) {
-	off := 8
-	binary.LittleEndian.PutUint32(d.buf[off:], length)
-
-	d.length = length
-}
-
 // Init initializes a virtual queue descriptor the given buffer length.
 func (d *Descriptor) Init(length int, flags uint16) {
 	addr, buf := dma.Reserve(length, 0)
@@ -74,6 +66,22 @@ func (d *Descriptor) Destroy() {
 	dma.Release(uint(d.Address))
 }
 
+// Read copies the contents of the descriptor buffer to b.
+func (d *Descriptor) Read(b []byte) {
+	copy(b, d.buf)
+}
+
+// Write copies the contents of b to the descriptor buffer, updating its length
+// field accordingly.
+func (d *Descriptor) Write(b []byte) {
+	off := 8
+	length := uint32(len(b))
+	binary.LittleEndian.PutUint32(d.buf[off:], length)
+
+	d.length = length
+	copy(d.buf, b)
+}
+
 // Available represents a VirtIO virtual queue Available ring buffer.
 //
 // All exported fields are used one-time at initialization, fields requiring
@@ -287,9 +295,9 @@ func (d *VirtualQueue) Pop() (buf []byte) {
 	}
 
 	avail := d.Used.Ring(d.Used.last % d.size)
-
 	buf = make([]byte, avail.Length)
-	copy(buf, d.Descriptors[avail.Index].buf)
+
+	d.Descriptors[avail.Index].Read(buf)
 
 	d.Available.index += 1
 	d.Available.SetRingIndex(d.Available.index%d.size, uint16(avail.Index))
@@ -305,21 +313,17 @@ func (d *VirtualQueue) Push(buf []byte) {
 	d.Lock()
 	defer d.Unlock()
 
-	length := len(buf)
 	index := d.Available.Ring(d.Available.index % d.size)
+	used := d.Used.Index() - d.Used.last
 
-	d.Descriptors[index].SetLength(uint32(length))
-	copy(d.Descriptors[index].buf, buf)
-
+	d.Descriptors[index].Write(buf)
 	d.Available.SetIndex(d.Available.index + 1)
 
-	for used := d.Used.Index() - d.Used.last; used > 0; used-- {
-		index = used - 1
-		avail := d.Used.Ring(used)
+	for i := used; i > 0; i-- {
+		avail := d.Used.Ring(i - 1)
 
 		d.Available.SetRingIndex(d.Available.index%d.size, uint16(avail.Index))
-		d.Used.last += 1
 	}
 
-	return
+	d.Used.last += used
 }
diff --git a/soc/nxp/i2c/i2c.go b/soc/nxp/i2c/i2c.go
index 7ab81814..2eca7e3e 100644
--- a/soc/nxp/i2c/i2c.go
+++ b/soc/nxp/i2c/i2c.go
@@ -276,7 +276,7 @@ func (hw *I2C) tx(buf []byte) (err error) {
 func (hw *I2C) start(repeat bool) (err error) {
 	var pos int
 
-	if repeat == false {
+	if !repeat {
 		// wait for bus to be free
 		if !reg.WaitFor16(hw.Timeout, hw.i2sr, I2SR_IBB, 1, 0) {
 			return errors.New("timeout waiting bus to be free")
@@ -296,7 +296,7 @@ func (hw *I2C) start(repeat bool) (err error) {
 		return errors.New("timeout waiting bus to be busy")
 	}
 
-	if repeat == false {
+	if !repeat {
 		// set Master Transmit mode
 		reg.Set16(hw.i2cr, I2CR_MTX)
 	}