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author | Jean Delvare <khali@linux-fr.org> | 2012-05-30 08:55:34 (GMT) |
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committer | Jean Delvare <khali@endymion.delvare> | 2012-05-30 08:55:34 (GMT) |
commit | 838bfa6049fb84dc66c9c9bbeb3a968ec987fd3d (patch) | |
tree | 5c6cf6d3d7dee7514f62b874b50bf88726144b11 /drivers | |
parent | 731a7378b81c2f5fa88ca1ae20b83d548d5613dc (diff) | |
download | linux-838bfa6049fb84dc66c9c9bbeb3a968ec987fd3d.tar.xz |
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>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/i2c/i2c-dev.c | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c index 4504832..5ec2261 100644 --- a/drivers/i2c/i2c-dev.c +++ b/drivers/i2c/i2c-dev.c @@ -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; |