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

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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>
This commit is contained in:
Shaveta Leekha 2014-04-24 14:51:23 +05:30 • committed by Heiko Schocher
parent dec1861be9
commit a405764c1e
1 changed files with 34 additions and 7 deletions
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41
drivers/i2c/fsl_i2c.c
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@ -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]; struct fsl_i2c *device = (struct fsl_i2c *)i2c_dev[adap->hwadapnr];
int i = -1; /* signal error */ int i = -1; /* signal error */
u8 *a = (u8*)&addr; u8 *a = (u8*)&addr;
int len = alen * -1;
if (i2c_wait4bus(adap) < 0) if (i2c_wait4bus(adap) < 0)
return -1; return -1;
if ((!length || alen > 0) /* To handle the need of I2C devices that require to write few bytes
&& i2c_write_addr(adap, dev, I2C_WRITE_BIT, 0) != 0 * (more than 4 bytes of address as in the case of else part)
&& __i2c_write(adap, &a[4 - alen], alen) == alen) * of data before reading, Negative equivalent of length(bytes to write)
i = 0; /* No error so far */ * 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 (length && if (i != len)
i2c_write_addr(adap, dev, I2C_READ_BIT, alen ? 1 : 0) != 0) return -1;
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); writeb(I2C_CR_MEN, &device->cr);