diff --git a/configs/stm32f429i-disco/src/stm32_lcd.c b/configs/stm32f429i-disco/src/stm32_lcd.c
index 581216274bc..bfce19f342a 100644
--- a/configs/stm32f429i-disco/src/stm32_lcd.c
+++ b/configs/stm32f429i-disco/src/stm32_lcd.c
@@ -502,7 +502,7 @@ int board_lcd_initialize(void)
             }
         }
 
-      return -errno;
+      return -ENODEV;
     }
 
   return OK;
diff --git a/configs/xtrs/src/xtr_serial.c b/configs/xtrs/src/xtr_serial.c
index 46d9cad72ef..ed2ef03fa80 100644
--- a/configs/xtrs/src/xtr_serial.c
+++ b/configs/xtrs/src/xtr_serial.c
@@ -266,8 +266,7 @@ static void up_detach(FAR struct uart_dev_s *dev)
 
 static int up_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 {
-  *get_errno_ptr() = ENOTTY;
-  return ERROR;
+  return -ENOTTY;
 }
 
 /****************************************************************************
diff --git a/configs/z80sim/src/z80_serial.c b/configs/z80sim/src/z80_serial.c
index 24cc42db768..ce5f9aa763c 100644
--- a/configs/z80sim/src/z80_serial.c
+++ b/configs/z80sim/src/z80_serial.c
@@ -215,8 +215,7 @@ static void up_detach(FAR struct uart_dev_s *dev)
 
 static int up_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 {
-  *get_errno_ptr() = ENOTTY;
-  return ERROR;
+  return -ENOTTY;
 }
 
 /****************************************************************************
diff --git a/drivers/lcd/ili9341.c b/drivers/lcd/ili9341.c
index c281ab86c34..ad31db450e9 100644
--- a/drivers/lcd/ili9341.c
+++ b/drivers/lcd/ili9341.c
@@ -1143,8 +1143,8 @@ static int ili9341_setcontrast(struct lcd_dev_s *dev, unsigned int contrast)
  *
  ****************************************************************************/
 
-FAR struct lcd_dev_s *ili9341_initialize(
-                        FAR struct ili9341_lcd_s *lcd, int devno)
+FAR struct lcd_dev_s *
+  ili9341_initialize(FAR struct ili9341_lcd_s *lcd, int devno)
 {
   if (lcd && devno >= 0 && devno < CONFIG_LCD_ILI9341_NINTERFACES)
     {
@@ -1175,15 +1175,12 @@ FAR struct lcd_dev_s *ili9341_initialize(
             {
               return &priv->dev;
             }
-
-          errno = EINVAL;
         }
     }
 
   return NULL;
 }
 
-
 /****************************************************************************
  * Name:  ili9341_clear
  *
diff --git a/drivers/sensors/lis331dl.c b/drivers/sensors/lis331dl.c
index c8a8cb9500b..a88abbea7dc 100644
--- a/drivers/sensors/lis331dl.c
+++ b/drivers/sensors/lis331dl.c
@@ -177,8 +177,7 @@ static int lis331dl_access(FAR struct lis331dl_dev_s *dev, uint8_t subaddr,
     }
   else
     {
-      errno = EFAULT;
-      return ERROR;
+      return -EFAULT;
     }
 
   if (length > 1)
@@ -240,7 +239,7 @@ static int lis331dl_readregs(FAR struct lis331dl_dev_s *dev)
 FAR struct lis331dl_dev_s *lis331dl_init(FAR struct i2c_master_s *i2c,
                                          uint16_t address)
 {
-  FAR struct lis331dl_dev_s * dev;
+  FAR struct lis331dl_dev_s *dev;
   uint8_t retval;
 
   ASSERT(i2c);
@@ -249,7 +248,6 @@ FAR struct lis331dl_dev_s *lis331dl_init(FAR struct i2c_master_s *i2c,
   dev = kmm_malloc(sizeof(struct lis331dl_dev_s));
   if (dev == NULL)
     {
-      errno = ENOMEM;
       return NULL;
     }
 
@@ -273,28 +271,14 @@ FAR struct lis331dl_dev_s *lis331dl_init(FAR struct i2c_master_s *i2c,
             {
               /* Normal exit point */
 
-              errno = 0;
               return dev;
             }
-
-          retval = errno;
         }
-
-      /* Otherwise, we mark an invalid device found at given address */
-
-      retval = ENODEV;
-    }
-  else
-    {
-      /* No response at given address is marked as */
-
-      retval = EFAULT;
     }
 
   /* Error exit */
 
   kmm_free(dev);
-  errno = retval;
   return NULL;
 }
 
@@ -412,7 +396,6 @@ lis331dl_getreadings(FAR struct lis331dl_dev_s * dev)
 
       if (!(retval[0] & ST_LIS331DL_SR_ZYXDA))
         {
-          errno = EAGAIN;
           return NULL;
         }
 
diff --git a/drivers/serial/uart_16550.c b/drivers/serial/uart_16550.c
index 49d10eaac75..3ba4a4f0569 100644
--- a/drivers/serial/uart_16550.c
+++ b/drivers/serial/uart_16550.c
@@ -444,9 +444,9 @@ static uart_dev_t g_uart3port =
 #  endif
 #endif
 
-/************************************************************************************
- * Inline Functions
- ************************************************************************************/
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
 
 /****************************************************************************
  * Name: u16550_serialin
@@ -487,7 +487,8 @@ static inline void u16550_disableuartint(FAR struct u16550_s *priv,
  * Name: u16550_restoreuartint
  ****************************************************************************/
 
-static inline void u16550_restoreuartint(FAR struct u16550_s *priv, uint32_t ier)
+static inline void u16550_restoreuartint(FAR struct u16550_s *priv,
+                                         uint32_t ier)
 {
   priv->ier |= ier & UART_IER_ALLIE;
   u16550_serialout(priv, UART_IER_OFFSET, priv->ier);
@@ -497,7 +498,8 @@ static inline void u16550_restoreuartint(FAR struct u16550_s *priv, uint32_t ier
  * Name: u16550_enablebreaks
  ****************************************************************************/
 
-static inline void u16550_enablebreaks(FAR struct u16550_s *priv, bool enable)
+static inline void u16550_enablebreaks(FAR struct u16550_s *priv,
+                                       bool enable)
 {
   uint32_t lcr = u16550_serialin(priv, UART_LCR_OFFSET);
 
@@ -513,7 +515,7 @@ static inline void u16550_enablebreaks(FAR struct u16550_s *priv, bool enable)
   u16550_serialout(priv, UART_LCR_OFFSET, lcr);
 }
 
-/************************************************************************************
+/****************************************************************************
  * Name: u16550_divisor
  *
  * Descrption:
@@ -524,7 +526,7 @@ static inline void u16550_enablebreaks(FAR struct u16550_s *priv, bool enable)
  *
  *   Ignoring the fractional divider for now.
  *
- ************************************************************************************/
+ ****************************************************************************/
 
 #ifndef CONFIG_16550_SUPRESS_CONFIG
 static inline uint32_t u16550_divisor(FAR struct u16550_s *priv)
@@ -533,10 +535,6 @@ static inline uint32_t u16550_divisor(FAR struct u16550_s *priv)
 }
 #endif
 
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
 /****************************************************************************
  * Name: u16550_setup
  *
@@ -547,7 +545,7 @@ static inline uint32_t u16550_divisor(FAR struct u16550_s *priv)
  *
  ****************************************************************************/
 
-static int u16550_setup(struct uart_dev_s *dev)
+static int u16550_setup(FAR struct uart_dev_s *dev)
 {
 #ifndef CONFIG_16550_SUPRESS_CONFIG
   FAR struct u16550_s *priv = (FAR struct u16550_s *)dev->priv;
@@ -676,6 +674,7 @@ static int u16550_attach(struct uart_dev_s *dev)
       up_enable_irq(priv->irq);
     }
 #endif
+
   return ret;
 }
 
@@ -711,10 +710,10 @@ static void u16550_detach(FAR struct uart_dev_s *dev)
 
 static int u16550_interrupt(int irq, FAR void *context, FAR void *arg)
 {
-  struct uart_dev_s *dev = (struct uart_dev_s *)arg;
-  struct u16550_s   *priv;
-  uint32_t           status;
-  int                passes;
+  FAR struct uart_dev_s *dev = (struct uart_dev_s *)arg;
+  FAR struct u16550_s *priv;
+  uint32_t status;
+  int passes;
 
   DEBUGASSERT(dev != NULL && dev->priv != NULL);
   priv = (FAR struct u16550_s *)dev->priv;
@@ -791,7 +790,7 @@ static int u16550_interrupt(int irq, FAR void *context, FAR void *arg)
 
           default:
             {
-              _err("ERROR: Unexpected IIR: %02x\n", status);
+              serr("ERROR: Unexpected IIR: %02x\n", status);
               break;
             }
         }
@@ -810,9 +809,9 @@ static int u16550_interrupt(int irq, FAR void *context, FAR void *arg)
 
 static int u16550_ioctl(struct file *filep, int cmd, unsigned long arg)
 {
-  struct inode      *inode = filep->f_inode;
-  struct uart_dev_s *dev   = inode->i_private;
-  struct u16550_s   *priv  = (FAR struct u16550_s *)dev->priv;
+  FAR struct inode *inode = filep->f_inode;
+  FAR struct uart_dev_s *dev   = inode->i_private;
+  FAR struct u16550_s *priv  = (FAR struct u16550_s *)dev->priv;
   int ret;
 
 #ifdef CONFIG_SERIAL_UART_ARCH_IOCTL
@@ -822,6 +821,7 @@ static int u16550_ioctl(struct file *filep, int cmd, unsigned long arg)
     {
       return ret;
     }
+
 #else
   ret = OK;
 #endif
@@ -834,8 +834,7 @@ static int u16550_ioctl(struct file *filep, int cmd, unsigned long arg)
         FAR struct u16550_s *user = (FAR struct u16550_s *)arg;
         if (!user)
           {
-            set_errno(EINVAL);
-            ret = ERROR;
+            ret = -EINVAL;
           }
         else
           {
@@ -863,8 +862,7 @@ static int u16550_ioctl(struct file *filep, int cmd, unsigned long arg)
       break;
 
     default:
-      set_errno(ENOTTY);
-      ret = ERROR;
+      ret = -ENOTTY;
       break;
     }
 
@@ -902,6 +900,7 @@ static int u16550_receive(struct uart_dev_s *dev, uint32_t *status)
 static void u16550_rxint(struct uart_dev_s *dev, bool enable)
 {
   FAR struct u16550_s *priv = (FAR struct u16550_s *)dev->priv;
+
   if (enable)
     {
       priv->ier |= UART_IER_ERBFI;
diff --git a/drivers/wireless/cc1101.c b/drivers/wireless/cc1101.c
index 33112b42a56..9c008f798d8 100644
--- a/drivers/wireless/cc1101.c
+++ b/drivers/wireless/cc1101.c
@@ -335,7 +335,7 @@ void cc1101_access_end(FAR struct cc1101_dev_s *dev)
  *        however
  *
  * Returned Value:
- *   OK on success or errno is set.
+ *   OK on success or a negated errno value on any failure.
  */
 
 int cc1101_access(FAR struct cc1101_dev_s *dev, uint8_t addr,
@@ -350,7 +350,7 @@ int cc1101_access(FAR struct cc1101_dev_s *dev, uint8_t addr,
 
   if ((addr & CC1101_READ_SINGLE) && length != 1)
     {
-      return ERROR;
+      return -EINVAL;
     }
 
   /* Prepare SPI */
@@ -396,7 +396,6 @@ int cc1101_access(FAR struct cc1101_dev_s *dev, uint8_t addr,
     }
 
   cc1101_access_end(dev);
-
   return stabyte;
 }
 
@@ -435,7 +434,7 @@ int cc1101_checkpart(struct cc1101_dev_s *dev)
   if (cc1101_access(dev, CC1101_PARTNUM, &partnum, 1) < 0 ||
       cc1101_access(dev, CC1101_VERSION, &version, 1) < 0)
     {
-      return ERROR;
+      return -ENODEV;
     }
 
   if (partnum == CC1101_PARTNUM_VALUE && version == CC1101_VERSION_VALUE)
@@ -443,7 +442,7 @@ int cc1101_checkpart(struct cc1101_dev_s *dev)
       return OK;
     }
 
-  return ERROR;
+  return -ENOTSUP;
 }
 
 void cc1101_dumpregs(struct cc1101_dev_s *dev, uint8_t addr, uint8_t length)
@@ -524,16 +523,17 @@ int cc1101_eventcb(int irq, FAR void *context)
  * Public Functions
  ****************************************************************************/
 
-struct cc1101_dev_s *cc1101_init(struct spi_dev_s *spi, uint8_t isrpin,
-    uint32_t pinset, const struct c1101_rfsettings_s *rfsettings)
+FAR struct cc1101_dev_s *
+  cc1101_init(FAR struct spi_dev_s *spi, uint8_t isrpin,
+              uint32_t pinset,
+              FAR const struct c1101_rfsettings_s *rfsettings)
 {
-  struct cc1101_dev_s *dev;
+  FAR struct cc1101_dev_s *dev;
 
   ASSERT(spi);
 
   if ((dev = kmm_malloc(sizeof(struct cc1101_dev_s))) == NULL)
     {
-      errno = ENOMEM;
       return NULL;
     }
 
@@ -550,7 +550,6 @@ struct cc1101_dev_s *cc1101_init(struct spi_dev_s *spi, uint8_t isrpin,
   if (cc1101_reset(dev) < 0)
     {
       kmm_free(dev);
-      errno = EFAULT;
       return NULL;
     }
 
@@ -559,7 +558,6 @@ struct cc1101_dev_s *cc1101_init(struct spi_dev_s *spi, uint8_t isrpin,
   if (cc1101_checkpart(dev) < 0)
     {
       kmm_free(dev);
-      errno = ENODEV;
       return NULL;
     }
 
@@ -667,24 +665,24 @@ int cc1101_setrf(struct cc1101_dev_s *dev, const struct c1101_rfsettings_s *sett
 
   if (cc1101_access(dev, CC1101_FSCTRL1, (FAR uint8_t *)&settings->FSCTRL1, -11) < 0)
     {
-      return ERROR;
+      return -EIO;
     }
 
   if (cc1101_access(dev, CC1101_FOCCFG,  (FAR uint8_t *)&settings->FOCCFG,  -5) < 0)
     {
-      return ERROR;
+      return -EIO;
     }
 
   if (cc1101_access(dev, CC1101_FREND1,  (FAR uint8_t *)&settings->FREND1,  -6) < 0)
     {
-      return ERROR;
+      return -EIO;
     }
 
   /* Load Power Table */
 
   if (cc1101_access(dev, CC1101_PATABLE, (FAR uint8_t *)settings->PA, -8) < 0)
     {
-      return ERROR;
+      return -EIO;
     }
 
   /* If channel is out of valid range, mark that. Limit power.