diff --git a/README.md b/README.md
index 3de4c2c..13b2dcb 100644
--- a/README.md
+++ b/README.md
@@ -83,10 +83,10 @@ your platform.
 **Every commit is [tested on real hardware](doc/drivers/CONTRIBUTING.md#testing)
 via [gohci](https://github.com/maruel/gohci) workers.**
 
-We gladly accept contributions from device driver developers via GitHub pull
-requests, as long as the author has signed the Google Contributor License.
-Please see [doc/drivers/CONTRIBUTING.md](doc/drivers/CONTRIBUTING.md) for more
-details.
+We gladly accept contributions for documentation improvements and from device
+driver developers via GitHub pull requests, as long as the author has signed the
+Google Contributor License. Please see
+[doc/drivers/CONTRIBUTING.md](doc/drivers/CONTRIBUTING.md) for more details.
 
 
 ## Philosophy
diff --git a/devices/apa102/apa102.go b/devices/apa102/apa102.go
index 2f5eb11..c97a911 100644
--- a/devices/apa102/apa102.go
+++ b/devices/apa102/apa102.go
@@ -300,6 +300,6 @@ func New(s spi.Conn, numLights int, intensity uint8, temperature uint16) (*Dev,
 
 //
 
-var errLength = errors.New("invalid RGB stream length")
+var errLength = errors.New("apa102: invalid RGB stream length")
 
 var _ devices.Display = &Dev{}
diff --git a/devices/bme280/bme280.go b/devices/bme280/bme280.go
index 7d85825..df77a5a 100644
--- a/devices/bme280/bme280.go
+++ b/devices/bme280/bme280.go
@@ -146,7 +146,7 @@ func NewI2C(b i2c.Bus, opts *Opts) (*Dev, error) {
 		case 0x00:
 			// do not do anything
 		default:
-			return nil, errors.New("given address not supported by device")
+			return nil, errors.New("bme280: given address not supported by device")
 		}
 	}
 	d := &Dev{d: &i2c.Dev{Bus: b, Addr: addr}, isSPI: false}
@@ -232,7 +232,7 @@ func (d *Dev) makeDev(opts *Opts) error {
 		return err
 	}
 	if chipID[0] != 0x60 {
-		return errors.New("unexpected chip id; is this a BME280?")
+		return errors.New("bme280: unexpected chip id; is this a BME280?")
 	}
 	// Read calibration data t1~3, p1~9, 8bits padding, h1.
 	var tph [0xA2 - 0x88]byte
diff --git a/devices/devicestest/display.go b/devices/devicestest/display.go
index 7f177ae..7cbfa81 100644
--- a/devices/devicestest/display.go
+++ b/devices/devicestest/display.go
@@ -21,7 +21,7 @@ type Display struct {
 // Write implements devices.Display.
 func (d *Display) Write(pixels []byte) (int, error) {
 	if len(pixels)%3 != 0 {
-		return 0, errors.New("invalid RGB stream length")
+		return 0, errors.New("devicetest: invalid RGB stream length")
 	}
 	copy(d.Img.Pix, pixels)
 	return len(pixels), nil
diff --git a/devices/ssd1306/image1bit/image1bit.go b/devices/ssd1306/image1bit/image1bit.go
index 6ddf1ca..baa5b85 100644
--- a/devices/ssd1306/image1bit/image1bit.go
+++ b/devices/ssd1306/image1bit/image1bit.go
@@ -56,7 +56,7 @@ func New(r image.Rectangle) (*Image, error) {
 	h := r.Dy()
 	w := r.Dx()
 	if h&7 != 0 {
-		return nil, errors.New("height must be multiple of 8")
+		return nil, errors.New("image1bit: height must be multiple of 8")
 	}
 	return &Image{w, h, make([]byte, w*h/8)}, nil
 }
diff --git a/devices/ssd1306/ssd1306.go b/devices/ssd1306/ssd1306.go
index 503a51d..798fb8c 100644
--- a/devices/ssd1306/ssd1306.go
+++ b/devices/ssd1306/ssd1306.go
@@ -20,6 +20,7 @@ package ssd1306
 
 import (
 	"errors"
+	"fmt"
 	"image"
 	"image/color"
 	"io"
@@ -95,16 +96,12 @@ func NewI2C(i i2c.Bus, w, h int, rotated bool) (*Dev, error) {
 // newDev is the common initialization code that is independent of the bus
 // being used.
 func newDev(dev io.Writer, w, h int, rotated bool) (*Dev, error) {
-	if w&7 != 0 || h&7 != 0 {
-		return nil, errors.New("height and width must be multiple of 8")
+	if w < 8 || w > 128 || w&7 != 0 {
+		return nil, fmt.Errorf("ssd1306: invalid width %d", w)
 	}
-	if w < 8 || w > 128 {
-		return nil, errors.New("invalid height")
+	if h < 8 || h > 64 || h&7 != 0 {
+		return nil, fmt.Errorf("ssd1306: invalid height %d", h)
 	}
-	if h < 8 || h > 64 {
-		return nil, errors.New("invalid width")
-	}
-
 	d := &Dev{w: dev, W: w, H: h}
 
 	contrast := byte(0x7F) // (default value)
@@ -226,7 +223,7 @@ func (d *Dev) Draw(r image.Rectangle, src image.Image, sp image.Point) {
 // the memory is effectively horizontal bands of 8 pixels high.
 func (d *Dev) Write(pixels []byte) (int, error) {
 	if len(pixels) != d.H*d.W/8 {
-		return 0, errors.New("invalid pixel stream")
+		return 0, errors.New("ssd1306: invalid pixel stream")
 	}
 
 	// Run as 2 big transactions to reduce downtime on the bus. Doing with one
diff --git a/experimental/devices/bitbang/i2c.go b/experimental/devices/bitbang/i2c.go
index b49aeec..725b8a1 100644
--- a/experimental/devices/bitbang/i2c.go
+++ b/experimental/devices/bitbang/i2c.go
@@ -54,7 +54,7 @@ func (i *I2C) Tx(addr uint16, w, r []byte) error {
 		if addr > 0xFF {
 			// Page 15, section 3.1.11 10-bit addressing
 			// TOOD(maruel): Implement if desired; prefix 0b11110xx.
-			return errors.New("invalid address")
+			return errors.New("bitbang-i2c: invalid address")
 		}
 		// Page 13, section 3.1.10 The slave address and R/W bit
 		addr <<= 1
@@ -66,7 +66,7 @@ func (i *I2C) Tx(addr uint16, w, r []byte) error {
 			return err
 		}
 		if !ack {
-			return errors.New("i2c: got NACK")
+			return errors.New("bitbang-i2c: got NACK")
 		}
 	}
 	for _, b := range w {
@@ -75,7 +75,7 @@ func (i *I2C) Tx(addr uint16, w, r []byte) error {
 			return err
 		}
 		if !ack {
-			return errors.New("i2c: got NACK")
+			return errors.New("bitbang-i2c: got NACK")
 		}
 	}
 	for x := range r {
diff --git a/experimental/devices/bitbang/spi.go b/experimental/devices/bitbang/spi.go
index 3dd13e2..a1591d6 100644
--- a/experimental/devices/bitbang/spi.go
+++ b/experimental/devices/bitbang/spi.go
@@ -71,7 +71,7 @@ func (s *SPI) Configure(mode spi.Mode, bits int) error {
 // BUG(maruel): Test if read works.
 func (s *SPI) Tx(w, r []byte) error {
 	if len(r) != 0 && len(w) != len(r) {
-		return errors.New("write and read buffers must be the same length")
+		return errors.New("bitbang-spi: write and read buffers must be the same length")
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
diff --git a/experimental/devices/piblaster/piblaster.go b/experimental/devices/piblaster/piblaster.go
index e784ee7..d82bac4 100644
--- a/experimental/devices/piblaster/piblaster.go
+++ b/experimental/devices/piblaster/piblaster.go
@@ -29,7 +29,7 @@ import (
 // duty must be [0, 1].
 func SetPWM(p gpio.PinIO, duty float32) error {
 	if duty < 0 || duty > 1 {
-		return fmt.Errorf("duty %f is invalid for blaster", duty)
+		return fmt.Errorf("piblaster: duty %f is invalid for blaster", duty)
 	}
 	err := openPiblaster()
 	if err == nil {