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i2c-dev: Add support for I2C_M_RECV_LEN 

As the bus driver side implementation of I2C_M_RECV_LEN is heavily
tied to SMBus, we can't support received length over 32 bytes, but
let's at least support that.

In practice, the caller will have to setup a buffer large enough to
cover the case where received length byte has value 32, so minimum
32 + 1 = 33 bytes, possibly more if there is a fixed number of bytes
added for the specific slave (for example a checksum.)

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
This commit is contained in:
Jean Delvare 2012-05-30 10:55:34 +02:00 committed by Jean Delvare
parent 731a7378b8
commit 838bfa6049
1 changed files with 26 additions and 4 deletions
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30
drivers/i2c/i2c-dev.c
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@ -265,19 +265,41 @@ static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,
res = 0;
for (i = 0; i < rdwr_arg.nmsgs; i++) {
/* Limit the size of the message to a sane amount;
* and don't let length change either. */
if ((rdwr_pa[i].len > 8192) ||
(rdwr_pa[i].flags & I2C_M_RECV_LEN)) {
/* Limit the size of the message to a sane amount */
if (rdwr_pa[i].len > 8192) {
res = -EINVAL;
break;
}
data_ptrs[i] = (u8 __user *)rdwr_pa[i].buf;
rdwr_pa[i].buf = memdup_user(data_ptrs[i], rdwr_pa[i].len);
if (IS_ERR(rdwr_pa[i].buf)) {
res = PTR_ERR(rdwr_pa[i].buf);
break;
}
/*
* If the message length is received from the slave (similar
* to SMBus block read), we must ensure that the buffer will
* be large enough to cope with a message length of
* I2C_SMBUS_BLOCK_MAX as this is the maximum underlying bus
* drivers allow. The first byte in the buffer must be
* pre-filled with the number of extra bytes, which must be
* at least one to hold the message length, but can be
* greater (for example to account for a checksum byte at
* the end of the message.)
*/
if (rdwr_pa[i].flags & I2C_M_RECV_LEN) {
if (!(rdwr_pa[i].flags & I2C_M_RD) ||
rdwr_pa[i].buf[0] < 1 ||
rdwr_pa[i].len < rdwr_pa[i].buf[0] +
I2C_SMBUS_BLOCK_MAX) {
res = -EINVAL;
break;
}
rdwr_pa[i].len = rdwr_pa[i].buf[0];
}
}
if (res < 0) {
int j;