Commit 838bfa60 authored by Jean Delvare's avatar Jean Delvare Committed by Jean Delvare
Browse files

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: default avatarJean Delvare <khali@linux-fr.org>
Tested-by: default avatarDouglas Gilbert <dgilbert@interlog.com>
parent 731a7378

drivers/i2c/i2c-dev.c

+26 −4
Original line number Diff line number Diff line
@@ -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;

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