Most of the I2C slaves support accesses in the typical style viz.read/write series of bytes at particular address offset. These transactions are currently supportd in the i2c driver using i2c_read and i2c_write APIs. I2C EEPROMs, RTC, etc fall in this category. The transactions look like:" 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: "START:Address:Tx:Txdata[0..n1]:Clock_stretching: RESTART:Address:Rx:data[0..n2]"
The 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. i2c_read() function has been modified to handle both types of transactions: the one that writes only offset/address before read and other that writes some bytes(more than 4 bytes) before read
To handle the case: Negative equivalent of length has been passed and interpreted accordinglt and txdata is being passed in rxdata buffer
Signed-off-by: Shaveta Leekha shaveta@freescale.com Signed-off-by: Poonam Aggrwal poonam.aggrwal@freescale.com --- drivers/i2c/fsl_i2c.c | 40 +++++++++++++++++++++++++++++++--------- 1 files changed, 31 insertions(+), 9 deletions(-)
diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c index 291ad94..14c66d0 100644 --- a/drivers/i2c/fsl_i2c.c +++ b/drivers/i2c/fsl_i2c.c @@ -424,17 +424,39 @@ fsl_i2c_read(struct i2c_adapter *adap, u8 dev, uint addr, int alen, u8 *data, int i = -1; /* signal error */ u8 *a = (u8*)&addr;
- if (i2c_wait4bus(adap) < 0) - return -1; + if (alen < 0) { + int len = alen * -1; + if (i2c_wait4bus(adap) < 0) + return -1; + + /* Generate a START and send the Address and + * the Tx Bytes to the slave. + * "START: Address: Write bytes wdata[wlength]" + * It supports writing any number of bytes in contrast + * to the else part, which supports writing address offset + * of upto 4 bytes only. + */ + 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, 1) != 0) + i = __i2c_read(adap, data, length); + } else { + 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 */ + 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); + 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);