From: David Brownell In Linus tree already: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=939bc4943d0483961edc45b63a7d27b4ffe547e3 This fixes a bug in the way i2c-algo-bit handles I2C_M_RECV_LEN, used to implement i2c_smbus_read_block_data(). Previously, in the absence of PEC (rarely used!) it would NAK the "length" byte: S addr Rd [A] [length] NA That prevents the subsequent data bytes from being read: S addr Rd [A] [length] { A [data] }* NA The primary fix just reorders two code blocks, so the length used in the "should I NAK now?" check incorporates the data which it just read from the slave device. However, that move also highlighted other fault handling glitches. This fixes those by abstracting the RX path ack/nak logic, so it can be used in more than one location. Signed-off-by: David Brownell Signed-off-by: Jean Delvare Signed-off-by: Greg Kroah-Hartman --- drivers/i2c/algos/i2c-algo-bit.c | 52 ++++++++++++++++++++++++--------------- 1 file changed, 32 insertions(+), 20 deletions(-) --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -357,13 +357,29 @@ static int sendbytes(struct i2c_adapter return wrcount; } +static int acknak(struct i2c_adapter *i2c_adap, int is_ack) +{ + struct i2c_algo_bit_data *adap = i2c_adap->algo_data; + + /* assert: sda is high */ + if (is_ack) /* send ack */ + setsda(adap, 0); + udelay((adap->udelay + 1) / 2); + if (sclhi(adap) < 0) { /* timeout */ + dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n"); + return -ETIMEDOUT; + } + scllo(adap); + return 0; +} + static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) { int inval; int rdcount=0; /* counts bytes read */ - struct i2c_algo_bit_data *adap = i2c_adap->algo_data; unsigned char *temp = msg->buf; int count = msg->len; + const unsigned flags = msg->flags; while (count > 0) { inval = i2c_inb(i2c_adap); @@ -377,28 +393,12 @@ static int readbytes(struct i2c_adapter temp++; count--; - if (msg->flags & I2C_M_NO_RD_ACK) { - bit_dbg(2, &i2c_adap->dev, "i2c_inb: 0x%02x\n", - inval); - continue; - } - - /* assert: sda is high */ - if (count) /* send ack */ - setsda(adap, 0); - udelay((adap->udelay + 1) / 2); - bit_dbg(2, &i2c_adap->dev, "i2c_inb: 0x%02x %s\n", inval, - count ? "A" : "NA"); - if (sclhi(adap)<0) { /* timeout */ - dev_err(&i2c_adap->dev, "readbytes: timeout at ack\n"); - return -ETIMEDOUT; - }; - scllo(adap); - /* Some SMBus transactions require that we receive the transaction length as the first read byte. */ - if (rdcount == 1 && (msg->flags & I2C_M_RECV_LEN)) { + if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) { if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) { + if (!(flags & I2C_M_NO_RD_ACK)) + acknak(i2c_adap, 0); dev_err(&i2c_adap->dev, "readbytes: invalid " "block length (%d)\n", inval); return -EREMOTEIO; @@ -409,6 +409,18 @@ static int readbytes(struct i2c_adapter count += inval; msg->len += inval; } + + bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n", + inval, + (flags & I2C_M_NO_RD_ACK) + ? "(no ack/nak)" + : (count ? "A" : "NA")); + + if (!(flags & I2C_M_NO_RD_ACK)) { + inval = acknak(i2c_adap, count); + if (inval < 0) + return inval; + } } return rdcount; } -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/