1 files changed, 177 insertions, 0 deletions
diff --git a/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/io/spi/devfs.go b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/io/spi/devfs.go
new file mode 100644
index 0000000..a5f1bca
--- /dev/null
+++ b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/io/spi/devfs.go
@@ -0,0 +1,177 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux
+// +build linux
+
+package spi
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/exp/io/spi/driver"
+)
+
+const (
+	devfs_MAGIC = 107
+
+	devfs_NRBITS   = 8
+	devfs_TYPEBITS = 8
+	devfs_SIZEBITS = 13
+	devfs_DIRBITS  = 3
+
+	devfs_NRSHIFT   = 0
+	devfs_TYPESHIFT = devfs_NRSHIFT + devfs_NRBITS
+	devfs_SIZESHIFT = devfs_TYPESHIFT + devfs_TYPEBITS
+	devfs_DIRSHIFT  = devfs_SIZESHIFT + devfs_SIZEBITS
+
+	devfs_READ  = 2
+	devfs_WRITE = 4
+)
+
+type payload struct {
+	tx       uint64
+	rx       uint64
+	length   uint32
+	speed    uint32
+	delay    uint16
+	bits     uint8
+	csChange uint8
+	txNBits  uint8
+	rxNBits  uint8
+	pad      uint16
+}
+
+// Devfs is an SPI driver that works against the devfs.
+// You need to have loaded the "spidev" Linux module to use this driver.
+type Devfs struct {
+	// Dev is the device to be opened.
+	// Device name is usually in the /dev/spidev<bus>.<chip> format.
+	// Required.
+	Dev string
+
+	// Mode is the SPI mode. SPI mode is a combination of polarity and phases.
+	// CPOL is the high order bit, CPHA is the low order. Pre-computed mode
+	// values are Mode0, Mode1, Mode2 and Mode3. The value of the mode argument
+	// can be overridden by the device's driver.
+	// Required.
+	Mode Mode
+
+	// MaxSpeed is the max clock speed (Hz) and can be overridden by the device's driver.
+	// Required.
+	MaxSpeed int64
+}
+
+// Open opens the provided device with the specified options
+// and returns a connection.
+func (d *Devfs) Open() (driver.Conn, error) {
+	f, err := os.OpenFile(d.Dev, os.O_RDWR, os.ModeDevice)
+	if err != nil {
+		return nil, err
+	}
+	conn := &devfsConn{f: f}
+	if err := conn.Configure(driver.Mode, int(d.Mode)); err != nil {
+		conn.Close()
+		return nil, err
+	}
+	if err := conn.Configure(driver.MaxSpeed, int(d.MaxSpeed)); err != nil {
+		conn.Close()
+		return nil, err
+	}
+	return conn, nil
+}
+
+type devfsConn struct {
+	f        *os.File
+	mode     uint8
+	speed    uint32
+	bits     uint8
+	delay    uint16
+	csChange uint8
+}
+
+func (c *devfsConn) Configure(k, v int) error {
+	switch k {
+	case driver.Mode:
+		m := uint8(v)
+		if err := c.ioctl(requestCode(devfs_WRITE, devfs_MAGIC, 1, 1), uintptr(unsafe.Pointer(&m))); err != nil {
+			return fmt.Errorf("error setting mode to %v: %v", m, err)
+		}
+		c.mode = m
+	case driver.Bits:
+		b := uint8(v)
+		if err := c.ioctl(requestCode(devfs_WRITE, devfs_MAGIC, 3, 1), uintptr(unsafe.Pointer(&b))); err != nil {
+			return fmt.Errorf("error setting bits per word to %v: %v", b, err)
+		}
+		c.bits = b
+	case driver.MaxSpeed:
+		s := uint32(v)
+		if err := c.ioctl(requestCode(devfs_WRITE, devfs_MAGIC, 4, 4), uintptr(unsafe.Pointer(&s))); err != nil {
+			return fmt.Errorf("error setting speed to %v: %v", s, err)
+		}
+		c.speed = s
+	case driver.Order:
+		o := uint8(v)
+		if err := c.ioctl(requestCode(devfs_WRITE, devfs_MAGIC, 2, 1), uintptr(unsafe.Pointer(&o))); err != nil {
+			return fmt.Errorf("error setting bit order to %v: %v", o, err)
+		}
+	case driver.Delay:
+		c.delay = uint16(v)
+	case driver.CSChange:
+		c.csChange = uint8(v)
+	default:
+		return fmt.Errorf("unknown key: %v", k)
+	}
+	return nil
+}
+
+func (c *devfsConn) Tx(w, r []byte) error {
+	if r == nil {
+		r = make([]byte, len(w))
+	}
+	// TODO(jbd): len(w) == len(r)?
+	// TODO(jbd): Allow nil w.
+	p := payload{
+		tx:       uint64(uintptr(unsafe.Pointer(&w[0]))),
+		rx:       uint64(uintptr(unsafe.Pointer(&r[0]))),
+		length:   uint32(len(w)),
+		speed:    c.speed,
+		delay:    c.delay,
+		bits:     c.bits,
+		csChange: c.csChange,
+	}
+	// TODO(jbd): Read from the device and fill rx.
+	return c.ioctl(msgRequestCode(1), uintptr(unsafe.Pointer(&p)))
+}
+
+func (c *devfsConn) Close() error {
+	return c.f.Close()
+}
+
+// requestCode returns the device specific request code for the specified direction,
+// type, number and size to be used in the ioctl call.
+func requestCode(dir, typ, nr, size uintptr) uintptr {
+	return (dir << devfs_DIRSHIFT) | (typ << devfs_TYPESHIFT) | (nr << devfs_NRSHIFT) | (size << devfs_SIZESHIFT)
+}
+
+// msgRequestCode returns the device specific value for the SPI
+// message payload to be used in the ioctl call.
+// n represents the number of messages.
+func msgRequestCode(n uint32) uintptr {
+	return uintptr(0x40006B00 + (n * 0x200000))
+}
+
+// ioctl makes an IOCTL on the open device file descriptor.
+func (c *devfsConn) ioctl(a1, a2 uintptr) error {
+	_, _, errno := syscall.Syscall(
+		syscall.SYS_IOCTL, c.f.Fd(), a1, a2,
+	)
+	if errno != 0 {
+		return syscall.Errno(errno)
+	}
+	return nil
+}