Commit a405764c1ec835a41ccda943b9156aee25e15d5e
Committed by
Heiko Schocher
Heiko Schocher
1 parent
dec1861be9
Exists in
v2017.01-smarct4x
and in
40 other branches
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>
Showing 1 changed file with 34 additions and 7 deletions Side-by-side Diff
drivers/i2c/fsl_i2c.c
| ... | ... | @@ -423,18 +423,45 @@ |
| 423 | 423 | struct fsl_i2c *device = (struct fsl_i2c *)i2c_dev[adap->hwadapnr]; |
| 424 | 424 | int i = -1; /* signal error */ |
| 425 | 425 | u8 *a = (u8*)&addr; |
| 426 | + int len = alen * -1; | |
| 426 | 427 | |
| 427 | 428 | if (i2c_wait4bus(adap) < 0) |
| 428 | 429 | return -1; |
| 429 | 430 | |
| 430 | - if ((!length || alen > 0) | |
| 431 | - && i2c_write_addr(adap, dev, I2C_WRITE_BIT, 0) != 0 | |
| 432 | - && __i2c_write(adap, &a[4 - alen], alen) == alen) | |
| 433 | - i = 0; /* No error so far */ | |
| 431 | + /* To handle the need of I2C devices that require to write few bytes | |
| 432 | + * (more than 4 bytes of address as in the case of else part) | |
| 433 | + * of data before reading, Negative equivalent of length(bytes to write) | |
| 434 | + * is passed, but used the +ve part of len for writing data | |
| 435 | + */ | |
| 436 | + if (alen < 0) { | |
| 437 | + /* Generate a START and send the Address and | |
| 438 | + * the Tx Bytes to the slave. | |
| 439 | + * "START: Address: Write bytes data[len]" | |
| 440 | + * IF part supports writing any number of bytes in contrast | |
| 441 | + * to the else part, which supports writing address offset | |
| 442 | + * of upto 4 bytes only. | |
| 443 | + * bytes that need to be written are passed in | |
| 444 | + * "data", which will eventually keep the data READ, | |
| 445 | + * after writing the len bytes out of it | |
| 446 | + */ | |
| 447 | + if (i2c_write_addr(adap, dev, I2C_WRITE_BIT, 0) != 0) | |
| 448 | + i = __i2c_write(adap, data, len); | |
| 434 | 449 | |
| 435 | - if (length && | |
| 436 | - i2c_write_addr(adap, dev, I2C_READ_BIT, alen ? 1 : 0) != 0) | |
| 437 | - i = __i2c_read(adap, data, length); | |
| 450 | + if (i != len) | |
| 451 | + return -1; | |
| 452 | + | |
| 453 | + if (length && i2c_write_addr(adap, dev, I2C_READ_BIT, 1) != 0) | |
| 454 | + i = __i2c_read(adap, data, length); | |
| 455 | + } else { | |
| 456 | + if ((!length || alen > 0) && | |
| 457 | + i2c_write_addr(adap, dev, I2C_WRITE_BIT, 0) != 0 && | |
| 458 | + __i2c_write(adap, &a[4 - alen], alen) == alen) | |
| 459 | + i = 0; /* No error so far */ | |
| 460 | + | |
| 461 | + if (length && | |
| 462 | + i2c_write_addr(adap, dev, I2C_READ_BIT, alen ? 1 : 0) != 0) | |
| 463 | + i = __i2c_read(adap, data, length); | |
| 464 | + } | |
| 438 | 465 | |
| 439 | 466 | writeb(I2C_CR_MEN, &device->cr); |
| 440 | 467 |