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 --- Changes for v2: Incorporated review comments of v1 Add driver's path in the subject line to make it more clear (older patch with different subject line has been discarded http://patchwork.ozlabs.org/patch/336911/)
drivers/i2c/fsl_i2c.c | 41 ++++++++++++++++++++++++++++++++++------- 1 files changed, 34 insertions(+), 7 deletions(-)
diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c index 291ad94..aa159f8 100644 --- 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);