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Diffstat (limited to '')
-rw-r--r-- | dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/io/spi/devfs.go | 177 |
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 +} |