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/chips/max6875.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/i2c/chips/max6875.c') diff --git a/drivers/i2c/chips/max6875.c b/drivers/i2c/chips/max6875.c index 76645c142977..e9e9e5171b53 100644 --- a/drivers/i2c/chips/max6875.c +++ b/drivers/i2c/chips/max6875.c @@ -106,6 +106,7 @@ static void max6875_update_slice(struct i2c_client *client, int slice) I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { if (i2c_smbus_read_i2c_block_data(client, MAX6875_CMD_BLK_READ, + SLICE_SIZE, buf) != SLICE_SIZE) { goto exit_up; } -- cgit v1.2.3-55-g7522