[media] em28xx: fix+improve+unify i2c error handling, debug messages and code comments

- do not pass USB specific error codes to userspace/i2c-subsystem
- unify the returned error codes and make them compliant with
  the i2c subsystem spec
- check number of actually transferred bytes (via USB) everywehere
- fix/improve debug messages
- improve code comments

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 89 insertions, 32 deletions

diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
index 6916e87bc624..80f87bbbd554 100644
--- a/drivers/media/usb/em28xx/em28xx-core.c
+++ b/drivers/media/usb/em28xx/em28xx-core.c
@@ -101,7 +101,7 @@ int em28xx_read_reg_req_len(struct em28xx *dev, u8 req, u16 reg,
                 if (reg_debug)
                         printk(" failed!\n");
                 mutex_unlock(&dev->ctrl_urb_lock);
-                return ret;
+                return usb_translate_errors(ret);
         }
 
         if (len)
@@ -182,6 +182,9 @@ int em28xx_write_regs_req(struct em28xx *dev, u8 req, u16 reg, char *buf,
                               0x0000, reg, dev->urb_buf, len, HZ);
         mutex_unlock(&dev->ctrl_urb_lock);
 
+        if (ret < 0)
+                return usb_translate_errors(ret);
+
         if (dev->wait_after_write)
                 msleep(dev->wait_after_write);
 
diff --git a/drivers/media/usb/em28xx/em28xx-i2c.c b/drivers/media/usb/em28xx/em28xx-i2c.c
index 4a24ed08e46a..f784b516ae1c 100644
--- a/drivers/media/usb/em28xx/em28xx-i2c.c
+++ b/drivers/media/usb/em28xx/em28xx-i2c.c
@@ -76,18 +76,26 @@ static int em2800_i2c_send_bytes(struct em28xx *dev, u8 addr, u8 *buf, u16 len)
         /* trigger write */
         ret = dev->em28xx_write_regs(dev, 4 - len, &b2[4 - len], 2 + len);
         if (ret != 2 + len) {
-                em28xx_warn("writing to i2c device failed (error=%i)\n", ret);
-                return -EIO;
+                em28xx_warn("failed to trigger write to i2c address 0x%x "
+                            "(error=%i)\n", addr, ret);
+                return (ret < 0) ? ret : -EIO;
         }
         /* wait for completion */
         for (write_timeout = EM2800_I2C_XFER_TIMEOUT; write_timeout > 0;
              write_timeout -= 5) {
                 ret = dev->em28xx_read_reg(dev, 0x05);
-                if (ret == 0x80 + len - 1)
+                if (ret == 0x80 + len - 1) {
                         return len;
+                } else if (ret == 0x94 + len - 1) {
+                        return -ENODEV;
+                } else if (ret < 0) {
+                        em28xx_warn("failed to get i2c transfer status from "
+                                    "bridge register (error=%i)\n", ret);
+                        return ret;
+                }
                 msleep(5);
         }
-        em28xx_warn("i2c write timed out\n");
+        em28xx_warn("write to i2c device at 0x%x timed out\n", addr);
         return -EIO;
 }
 
@@ -168,24 +176,48 @@ static int em2800_i2c_check_for_device(struct em28xx *dev, u8 addr)
 static int em28xx_i2c_send_bytes(struct em28xx *dev, u16 addr, u8 *buf,
                                  u16 len, int stop)
 {
-        int wrcount = 0;
         int write_timeout, ret;
 
         if (len < 1 || len > 64)
                 return -EOPNOTSUPP;
+        /* NOTE: limited by the USB ctrl message constraints
+         * Zero length reads always succeed, even if no device is connected */
 
-        wrcount = dev->em28xx_write_regs_req(dev, stop ? 2 : 3, addr, buf, len);
+        /* Write to i2c device */
+        ret = dev->em28xx_write_regs_req(dev, stop ? 2 : 3, addr, buf, len);
+        if (ret != len) {
+                if (ret < 0) {
+                        em28xx_warn("writing to i2c device at 0x%x failed "
+                                    "(error=%i)\n", addr, ret);
+                        return ret;
+                } else {
+                        em28xx_warn("%i bytes write to i2c device at 0x%x "
+                                    "requested, but %i bytes written\n",
+                                    len, addr, ret);
+                        return -EIO;
+                }
+        }
 
-        /* Seems to be required after a write */
+        /* Check success of the i2c operation */
         for (write_timeout = EM2800_I2C_XFER_TIMEOUT; write_timeout > 0;
              write_timeout -= 5) {
                 ret = dev->em28xx_read_reg(dev, 0x05);
-                if (!ret)
-                        break;
+                if (ret == 0) { /* success */
+                        return len;
+                } else if (ret == 0x10) {
+                        return -ENODEV;
+                } else if (ret < 0) {
+                        em28xx_warn("failed to read i2c transfer status from "
+                                    "bridge (error=%i)\n", ret);
+                        return ret;
+                }
                 msleep(5);
+                /* NOTE: do we really have to wait for success ?
+                   Never seen anything else than 0x00 or 0x10
+                   (even with high payload) ...                 */
         }
-
-        return wrcount;
+        em28xx_warn("write to i2c device at 0x%x timed out\n", addr);
+        return -EIO;
 }
 
 /*
@@ -198,15 +230,40 @@ static int em28xx_i2c_recv_bytes(struct em28xx *dev, u16 addr, u8 *buf, u16 len)
 
         if (len < 1 || len > 64)
                 return -EOPNOTSUPP;
+        /* NOTE: limited by the USB ctrl message constraints
+         * Zero length reads always succeed, even if no device is connected */
 
+        /* Read data from i2c device */
         ret = dev->em28xx_read_reg_req_len(dev, 2, addr, buf, len);
+        if (ret != len) {
+                if (ret < 0) {
+                        em28xx_warn("reading from i2c device at 0x%x failed "
+                                    "(error=%i)\n", addr, ret);
+                        return ret;
+                } else {
+                        em28xx_warn("%i bytes requested from i2c device at "
+                                    "0x%x, but %i bytes received\n",
+                                    len, addr, ret);
+                        return -EIO;
+                }
+        }
+
+        /* Check success of the i2c operation */
+        ret = dev->em28xx_read_reg(dev, 0x05);
         if (ret < 0) {
-                em28xx_warn("reading i2c device failed (error=%i)\n", ret);
+                em28xx_warn("failed to read i2c transfer status from "
+                            "bridge (error=%i)\n", ret);
                 return ret;
         }
-        if (dev->em28xx_read_reg(dev, 0x5) != 0)
-                return -ENODEV;
-        return ret;
+        if (ret > 0) {
+                if (ret == 0x10) {
+                        return -ENODEV;
+                } else {
+                        em28xx_warn("unknown i2c error (status=%i)\n", ret);
+                        return -EIO;
+                }
+        }
+        return len;
 }
 
 /*
@@ -216,15 +273,12 @@ static int em28xx_i2c_recv_bytes(struct em28xx *dev, u16 addr, u8 *buf, u16 len)
 static int em28xx_i2c_check_for_device(struct em28xx *dev, u16 addr)
 {
         int ret;
+        u8 buf;
 
-        ret = dev->em28xx_read_reg_req(dev, 2, addr);
-        if (ret < 0) {
-                em28xx_warn("reading from i2c device failed (error=%i)\n", ret);
-                return ret;
-        }
-        if (dev->em28xx_read_reg(dev, 0x5) != 0)
-                return -ENODEV;
-        return 0;
+        ret = em28xx_i2c_recv_bytes(dev, addr, &buf, 1);
+        if (ret == 1)
+                return 0;
+        return (ret < 0) ? ret : -EIO;
 }
 
 /*
@@ -249,11 +303,11 @@ static int em28xx_i2c_xfer(struct i2c_adapter *i2c_adap,
                                 rc = em2800_i2c_check_for_device(dev, addr);
                         else
                                 rc = em28xx_i2c_check_for_device(dev, addr);
-                        if (rc < 0) {
-                                dprintk2(2, " no device\n");
+                        if (rc == -ENODEV) {
+                                if (i2c_debug >= 2)
+                                        printk(" no device\n");
                                 return rc;
                         }
-
                 } else if (msgs[i].flags & I2C_M_RD) {
                         /* read bytes */
                         if (dev->board.is_em2800)
@@ -284,16 +338,16 @@ static int em28xx_i2c_xfer(struct i2c_adapter *i2c_adap,
                                                            msgs[i].len,
                                                            i == num - 1);
                 }
-                if (rc < 0)
-                        goto err;
+                if (rc < 0) {
+                        if (i2c_debug >= 2)
+                                printk(" ERROR: %i\n", rc);
+                        return rc;
+                }
                 if (i2c_debug >= 2)
                         printk("\n");
         }
 
         return num;
-err:
-        dprintk2(2, " ERROR: %i\n", rc);
-        return rc;
 }
 
 /* based on linux/sunrpc/svcauth.h and linux/hash.h