1 files changed, 26 insertions, 8 deletions

diff --git a/drivers/media/dvb/dvb-usb/af9035.c b/drivers/media/dvb/dvb-usb/af9035.c
index 73044632d943..58fe69deda1f 100644
--- a/drivers/media/dvb/dvb-usb/af9035.c
+++ b/drivers/media/dvb/dvb-usb/af9035.c
@@ -224,6 +224,22 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
         if (mutex_lock_interruptible(&d->i2c_mutex) < 0)
                 return -EAGAIN;
 
+        /*
+         * I2C sub header is 5 bytes long. Meaning of those bytes are:
+         * 0: data len
+         * 1: I2C addr << 1
+         * 2: reg addr len
+         *    byte 3 and 4 can be used as reg addr
+         * 3: reg addr MSB
+         *    used when reg addr len is set to 2
+         * 4: reg addr LSB
+         *    used when reg addr len is set to 1 or 2
+         *
+         * For the simplify we do not use register addr at all.
+         * NOTE: As a firmware knows tuner type there is very small possibility
+         * there could be some tuner I2C hacks done by firmware and this may
+         * lead problems if firmware expects those bytes are used.
+         */
         if (num == 2 && !(msg[0].flags & I2C_M_RD) &&
                         (msg[1].flags & I2C_M_RD)) {
                 if (msg[0].len > 40 || msg[1].len > 40) {
@@ -237,14 +253,15 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
                                         msg[1].len);
                 } else {
                         /* I2C */
-                        u8 buf[4 + msg[0].len];
+                        u8 buf[5 + msg[0].len];
                         struct usb_req req = { CMD_I2C_RD, 0, sizeof(buf),
                                         buf, msg[1].len, msg[1].buf };
                         buf[0] = msg[1].len;
                         buf[1] = msg[0].addr << 1;
-                        buf[2] = 0x01;
-                        buf[3] = 0x00;
-                        memcpy(&buf[4], msg[0].buf, msg[0].len);
+                        buf[2] = 0x00; /* reg addr len */
+                        buf[3] = 0x00; /* reg addr MSB */
+                        buf[4] = 0x00; /* reg addr LSB */
+                        memcpy(&buf[5], msg[0].buf, msg[0].len);
                         ret = af9035_ctrl_msg(d->udev, &req);
                 }
         } else if (num == 1 && !(msg[0].flags & I2C_M_RD)) {
@@ -259,14 +276,15 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
                                         msg[0].len - 3);
                 } else {
                         /* I2C */
-                        u8 buf[4 + msg[0].len];
+                        u8 buf[5 + msg[0].len];
                         struct usb_req req = { CMD_I2C_WR, 0, sizeof(buf), buf,
                                         0, NULL };
                         buf[0] = msg[0].len;
                         buf[1] = msg[0].addr << 1;
-                        buf[2] = 0x01;
-                        buf[3] = 0x00;
-                        memcpy(&buf[4], msg[0].buf, msg[0].len);
+                        buf[2] = 0x00; /* reg addr len */
+                        buf[3] = 0x00; /* reg addr MSB */
+                        buf[4] = 0x00; /* reg addr LSB */
+                        memcpy(&buf[5], msg[0].buf, msg[0].len);
                         ret = af9035_ctrl_msg(d->udev, &req);
                 }
         } else {