2 files changed, 49 insertions, 115 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 0040981b6698..02e335a04f09 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -19,7 +19,8 @@
 
 /* With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>.
    All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
-   SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com>                */
+   SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and
+   Jean Delvare <khali@linux-fr.org> */
 
 #include <linux/module.h>
 #include <linux/kernel.h>
@@ -830,101 +831,44 @@ crc8(u16 data)
         return (u8)(data >> 8);
 }
 
-/* CRC over count bytes in the first array plus the bytes in the rest
-   array if it is non-null. rest[0] is the (length of rest) - 1
-   and is included. */
-static u8 i2c_smbus_partial_pec(u8 crc, int count, u8 *first, u8 *rest)
+/* Incremental CRC8 over count bytes in the array pointed to by p */
+static u8 i2c_smbus_pec(u8 crc, u8 *p, size_t count)
 {
         int i;
 
         for(i = 0; i < count; i++)
-                crc = crc8((crc ^ first[i]) << 8);
-        if(rest != NULL)
-                for(i = 0; i <= rest[0]; i++)
-                        crc = crc8((crc ^ rest[i]) << 8);
+                crc = crc8((crc ^ p[i]) << 8);
         return crc;
 }
 
-static u8 i2c_smbus_pec(int count, u8 *first, u8 *rest)
+/* Assume a 7-bit address, which is reasonable for SMBus */
+static u8 i2c_smbus_msg_pec(u8 pec, struct i2c_msg *msg)
 {
-        return i2c_smbus_partial_pec(0, count, first, rest);
+        /* The address will be sent first */
+        u8 addr = (msg->addr << 1) | !!(msg->flags & I2C_M_RD);
+        pec = i2c_smbus_pec(pec, &addr, 1);
+
+        /* The data buffer follows */
+        return i2c_smbus_pec(pec, msg->buf, msg->len);
 }
 
-/* Returns new "size" (transaction type)
-   Note that we convert byte to byte_data and byte_data to word_data
-   rather than invent new xxx_PEC transactions. */
-static int i2c_smbus_add_pec(u16 addr, u8 command, int size,
-                             union i2c_smbus_data *data)
+/* Used for write only transactions */
+static inline void i2c_smbus_add_pec(struct i2c_msg *msg)
 {
-        u8 buf[3];
-
-        buf[0] = addr << 1;
-        buf[1] = command;
-        switch(size) {
-                case I2C_SMBUS_BYTE:
-                        data->byte = i2c_smbus_pec(2, buf, NULL);
-                        size = I2C_SMBUS_BYTE_DATA;
-                        break;
-                case I2C_SMBUS_BYTE_DATA:
-                        buf[2] = data->byte;
-                        data->word = buf[2] |
-                                    (i2c_smbus_pec(3, buf, NULL) << 8);
-                        size = I2C_SMBUS_WORD_DATA;
-                        break;
-                case I2C_SMBUS_WORD_DATA:
-                        /* unsupported */
-                        break;
-                case I2C_SMBUS_BLOCK_DATA:
-                        data->block[data->block[0] + 1] =
-                                     i2c_smbus_pec(2, buf, data->block);
-                        size = I2C_SMBUS_BLOCK_DATA_PEC;
-                        break;
-        }
-        return size;    
+        msg->buf[msg->len] = i2c_smbus_msg_pec(0, msg);
+        msg->len++;
 }
 
-static int i2c_smbus_check_pec(u16 addr, u8 command, int size, u8 partial,
-                               union i2c_smbus_data *data)
+/* Return <0 on CRC error
+   If there was a write before this read (most cases) we need to take the
+   partial CRC from the write part into account.
+   Note that this function does modify the message (we need to decrease the
+   message length to hide the CRC byte from the caller). */
+static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
 {
-        u8 buf[3], rpec, cpec;
+        u8 rpec = msg->buf[--msg->len];
+        cpec = i2c_smbus_msg_pec(cpec, msg);
 
-        buf[1] = command;
-        switch(size) {
-                case I2C_SMBUS_BYTE_DATA:
-                        buf[0] = (addr << 1) | 1;
-                        cpec = i2c_smbus_pec(2, buf, NULL);
-                        rpec = data->byte;
-                        break;
-                case I2C_SMBUS_WORD_DATA:
-                        buf[0] = (addr << 1) | 1;
-                        buf[2] = data->word & 0xff;
-                        cpec = i2c_smbus_pec(3, buf, NULL);
-                        rpec = data->word >> 8;
-                        break;
-                case I2C_SMBUS_WORD_DATA_PEC:
-                        /* unsupported */
-                        cpec = rpec = 0;
-                        break;
-                case I2C_SMBUS_PROC_CALL_PEC:
-                        /* unsupported */
-                        cpec = rpec = 0;
-                        break;
-                case I2C_SMBUS_BLOCK_DATA_PEC:
-                        buf[0] = (addr << 1);
-                        buf[2] = (addr << 1) | 1;
-                        cpec = i2c_smbus_pec(3, buf, data->block);
-                        rpec = data->block[data->block[0] + 1];
-                        break;
-                case I2C_SMBUS_BLOCK_PROC_CALL_PEC:
-                        buf[0] = (addr << 1) | 1;
-                        rpec = i2c_smbus_partial_pec(partial, 1,
-                                                     buf, data->block);
-                        cpec = data->block[data->block[0] + 1];
-                        break;
-                default:
-                        cpec = rpec = 0;
-                        break;
-        }
         if (rpec != cpec) {
                 pr_debug("i2c-core: Bad PEC 0x%02x vs. 0x%02x\n",
                         rpec, cpec);
@@ -951,9 +895,8 @@ s32 i2c_smbus_read_byte(struct i2c_client *client)
 
 s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value)
 {
-        union i2c_smbus_data data;      /* only for PEC */
         return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
-                              I2C_SMBUS_WRITE,value, I2C_SMBUS_BYTE,&data);
+                              I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
 }
 
 s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command)
@@ -1043,6 +986,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                                   { addr, flags | I2C_M_RD, 0, msgbuf1 }
                                 };
         int i;
+        u8 partial_pec = 0;
 
         msgbuf0[0] = command;
         switch(size) {
@@ -1085,7 +1029,6 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                 msgbuf0[2] = (data->word >> 8) & 0xff;
                 break;
         case I2C_SMBUS_BLOCK_DATA:
-        case I2C_SMBUS_BLOCK_DATA_PEC:
                 if (read_write == I2C_SMBUS_READ) {
                         dev_err(&adapter->dev, "Block read not supported "
                                "under I2C emulation!\n");
@@ -1098,14 +1041,11 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                                        data->block[0]);
                                 return -1;
                         }
-                        if(size == I2C_SMBUS_BLOCK_DATA_PEC)
-                                (msg[0].len)++;
                         for (i = 1; i < msg[0].len; i++)
                                 msgbuf0[i] = data->block[i-1];
                 }
                 break;
         case I2C_SMBUS_BLOCK_PROC_CALL:
-        case I2C_SMBUS_BLOCK_PROC_CALL_PEC:
                 dev_dbg(&adapter->dev, "Block process call not supported "
                        "under I2C emulation!\n");
                 return -1;
@@ -1130,9 +1070,30 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                 return -1;
         }
 
+        i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
+                                      && size != I2C_SMBUS_I2C_BLOCK_DATA);
+        if (i) {
+                /* Compute PEC if first message is a write */
+                if (!(msg[0].flags & I2C_M_RD)) {
+                        if (num == 1) /* Write only */
+                                i2c_smbus_add_pec(&msg[0]);
+                        else /* Write followed by read */
+                                partial_pec = i2c_smbus_msg_pec(0, &msg[0]);
+                }
+                /* Ask for PEC if last message is a read */
+                if (msg[num-1].flags & I2C_M_RD)
+                        msg[num-1].len++;
+        }
+
         if (i2c_transfer(adapter, msg, num) < 0)
                 return -1;
 
+        /* Check PEC if last message is a read */
+        if (i && (msg[num-1].flags & I2C_M_RD)) {
+                if (i2c_smbus_check_pec(partial_pec, &msg[num-1]) < 0)
+                        return -1;
+        }
+
         if (read_write == I2C_SMBUS_READ)
                 switch(size) {
                         case I2C_SMBUS_BYTE:
@@ -1161,28 +1122,8 @@ s32 i2c_smbus_xfer(struct i2c_adapter * adapter, u16 addr, unsigned short flags,
                    union i2c_smbus_data * data)
 {
         s32 res;
-        int swpec = 0;
-        u8 partial = 0;
 
         flags &= I2C_M_TEN | I2C_CLIENT_PEC;
-        if((flags & I2C_CLIENT_PEC) &&
-           !(i2c_check_functionality(adapter, I2C_FUNC_SMBUS_HWPEC_CALC))) {
-                swpec = 1;
-                if(read_write == I2C_SMBUS_READ &&
-                   size == I2C_SMBUS_BLOCK_DATA)
-                        size = I2C_SMBUS_BLOCK_DATA_PEC;
-                else if(size == I2C_SMBUS_PROC_CALL)
-                        size = I2C_SMBUS_PROC_CALL_PEC;
-                else if(size == I2C_SMBUS_BLOCK_PROC_CALL) {
-                        i2c_smbus_add_pec(addr, command,
-                                          I2C_SMBUS_BLOCK_DATA, data);
-                        partial = data->block[data->block[0] + 1];
-                        size = I2C_SMBUS_BLOCK_PROC_CALL_PEC;
-                } else if(read_write == I2C_SMBUS_WRITE &&
-                          size != I2C_SMBUS_QUICK &&
-                          size != I2C_SMBUS_I2C_BLOCK_DATA)
-                        size = i2c_smbus_add_pec(addr, command, size, data);
-        }
 
         if (adapter->algo->smbus_xfer) {
                 down(&adapter->bus_lock);
@@ -1193,13 +1134,6 @@ s32 i2c_smbus_xfer(struct i2c_adapter * adapter, u16 addr, unsigned short flags,
                 res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write,
                                               command,size,data);
 
-        if(res >= 0 && swpec &&
-           size != I2C_SMBUS_QUICK && size != I2C_SMBUS_I2C_BLOCK_DATA &&
-           (read_write == I2C_SMBUS_READ || size == I2C_SMBUS_PROC_CALL_PEC ||
-            size == I2C_SMBUS_BLOCK_PROC_CALL_PEC)) {
-                if(i2c_smbus_check_pec(addr, command, size, partial, data))
-                        return -1;
-        }
         return res;
 }
 
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index bcd4bb1b450c..78c64f7b3105 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -434,7 +434,7 @@ union i2c_smbus_data {
         __u8 byte;
         __u16 word;
         __u8 block[I2C_SMBUS_BLOCK_MAX + 2]; /* block[0] is used for length */
-                                                    /* and one more for PEC */
+                               /* and one more for user-space compatibility */
 };
 
 /* smbus_access read or write markers */