From 4b2643d7d9bdcd776749e17f73c168ddf02e93cb Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Thu, 12 Jul 2007 14:12:29 +0200 Subject: i2c: Fix the i2c_smbus_read_i2c_block_data() prototype Let the drivers specify how many bytes they want to read with i2c_smbus_read_i2c_block_data(). So far, the block count was hard-coded to I2C_SMBUS_BLOCK_MAX (32), which did not make much sense. Many driver authors complained about this before, and I believe it's about time to fix it. Right now, authors have to do technically stupid things, such as individual byte reads or full-fledged I2C messaging, to work around the problem. We do not want to encourage that. I even found that some bus drivers (e.g. i2c-amd8111) already implemented I2C block read the "right" way, that is, they didn't follow the old, broken standard. The fact that it was never noticed before just shows how little i2c_smbus_read_i2c_block_data() was used, which isn't that surprising given how broken its prototype was so far. There are some obvious compatiblity considerations: * This changes the i2c_smbus_read_i2c_block_data() prototype. Users outside the kernel tree will notice at compilation time, and will have to update their code. * User-space has access to i2c_smbus_xfer() directly using i2c-dev, so the changed expectations would affect tools such as i2cdump. In order to preserve binary compatibility, we give I2C_SMBUS_I2C_BLOCK_DATA a new numeric value, and define I2C_SMBUS_I2C_BLOCK_BROKEN with the old numeric value. When i2c-dev receives a transaction with the old value, it can convert it to the new format on the fly. Signed-off-by: Jean Delvare --- drivers/i2c/i2c-dev.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'drivers/i2c/i2c-dev.c') diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c index e7a70971059..64eee9551b2 100644 --- a/drivers/i2c/i2c-dev.c +++ b/drivers/i2c/i2c-dev.c @@ -283,6 +283,7 @@ static int i2cdev_ioctl(struct inode *inode, struct file *file, (data_arg.size != I2C_SMBUS_WORD_DATA) && (data_arg.size != I2C_SMBUS_PROC_CALL) && (data_arg.size != I2C_SMBUS_BLOCK_DATA) && + (data_arg.size != I2C_SMBUS_I2C_BLOCK_BROKEN) && (data_arg.size != I2C_SMBUS_I2C_BLOCK_DATA) && (data_arg.size != I2C_SMBUS_BLOCK_PROC_CALL)) { dev_dbg(&client->adapter->dev, @@ -329,10 +330,18 @@ static int i2cdev_ioctl(struct inode *inode, struct file *file, if ((data_arg.size == I2C_SMBUS_PROC_CALL) || (data_arg.size == I2C_SMBUS_BLOCK_PROC_CALL) || + (data_arg.size == I2C_SMBUS_I2C_BLOCK_DATA) || (data_arg.read_write == I2C_SMBUS_WRITE)) { if (copy_from_user(&temp, data_arg.data, datasize)) return -EFAULT; } + if (data_arg.size == I2C_SMBUS_I2C_BLOCK_BROKEN) { + /* Convert old I2C block commands to the new + convention. This preserves binary compatibility. */ + data_arg.size = I2C_SMBUS_I2C_BLOCK_DATA; + if (data_arg.read_write == I2C_SMBUS_READ) + temp.block[0] = I2C_SMBUS_BLOCK_MAX; + } res = i2c_smbus_xfer(client->adapter,client->addr,client->flags, data_arg.read_write, data_arg.command,data_arg.size,&temp); -- cgit v1.2.3