drivers/i2c/fsl_i2c: modify i2c_read to handle multi-byte write

Most of the I2C slaves support accesses in the typical style
that is : read/write series of bytes at particular address offset.
These transactions look like:"
(1) START:Address:Tx:Offset:RESTART:Address[0..4]:Tx/Rx:data[0..n]:STOP"

However there are certain devices which support accesses in
terms of the transactions as follows:
(2) "START:Address:Tx:Txdata[0..n1]:Clock_stretching:
        RESTART:Address:Rx:data[0..n2]"
Here Txdata is typically a command and some associated data,
similarly Rxdata could be command status plus some data received
as a response to the command sent.

Type (1) transactions are currently supportd in the
i2c driver using i2c_read and i2c_write APIs. I2C EEPROMs,
RTC, etc fall in this category.

To handle type (2) along with type (1) transactions,
i2c_read() function has been modified.

Signed-off-by: Shaveta Leekha <shaveta@freescale.com>
Signed-off-by: Poonam Aggrwal <poonam.aggrwal@freescale.com>

diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c
index 291ad94..aa159f8 100644 (file)
--- a/drivers/i2c/fsl_i2c.c
+++ b/drivers/i2c/fsl_i2c.c
@@ -423,18 +423,45 @@ fsl_i2c_read(struct i2c_adapter *adap, u8 dev, uint addr, int alen, u8 *data,
        struct fsl_i2c *device = (struct fsl_i2c *)i2c_dev[adap->hwadapnr];
        int i = -1; /* signal error */
        u8 *a = (u8*)&addr;
+       int len = alen * -1;
 
        if (i2c_wait4bus(adap) < 0)
                return -1;
 
-       if ((!length || alen > 0)
-           && i2c_write_addr(adap, dev, I2C_WRITE_BIT, 0) != 0
-           && __i2c_write(adap, &a[4 - alen], alen) == alen)
-               i = 0; /* No error so far */
+       /* To handle the need of I2C devices that require to write few bytes
+        * (more than 4 bytes of address as in the case of else part)
+        * of data before reading, Negative equivalent of length(bytes to write)
+        * is passed, but used the +ve part of len for writing data
+        */
+       if (alen < 0) {
+               /* Generate a START and send the Address and
+                * the Tx Bytes to the slave.
+                * "START: Address: Write bytes data[len]"
+                * IF part supports writing any number of bytes in contrast
+                * to the else part, which supports writing address offset
+                * of upto 4 bytes only.
+                * bytes that need to be written are passed in
+                * "data", which will eventually keep the data READ,
+                * after writing the len bytes out of it
+                */
+               if (i2c_write_addr(adap, dev, I2C_WRITE_BIT, 0) != 0)
+                       i = __i2c_write(adap, data, len);
+
+               if (i != len)
+                       return -1;
 
-       if (length &&
-           i2c_write_addr(adap, dev, I2C_READ_BIT, alen ? 1 : 0) != 0)
-               i = __i2c_read(adap, data, length);
+               if (length && i2c_write_addr(adap, dev, I2C_READ_BIT, 1) != 0)
+                       i = __i2c_read(adap, data, length);
+       } else {
+               if ((!length || alen > 0) &&
+                   i2c_write_addr(adap, dev, I2C_WRITE_BIT, 0) != 0  &&
+                   __i2c_write(adap, &a[4 - alen], alen) == alen)
+                       i = 0; /* No error so far */
+
+               if (length &&
+                   i2c_write_addr(adap, dev, I2C_READ_BIT, alen ? 1 : 0) != 0)
+                       i = __i2c_read(adap, data, length);
+       }
 
        writeb(I2C_CR_MEN, &device->cr);