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 <[email protected]>
Signed-off-by: Poonam Aggrwal <[email protected]>
---
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);
--
1.7.6.GIT
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