]> pilppa.com Git - linux-2.6-omap-h63xx.git/commit
i2c: Fix the i2c_smbus_read_i2c_block_data() prototype
authorJean Delvare <khali@linux-fr.org>
Thu, 12 Jul 2007 12:12:29 +0000 (14:12 +0200)
committerJean Delvare <khali@hyperion.delvare>
Thu, 12 Jul 2007 12:12:29 +0000 (14:12 +0200)
commit4b2643d7d9bdcd776749e17f73c168ddf02e93cb
tree1642900ea1c196cc27d120f0af4de44fff30633e
parentba7fbb723f50ab2607989a282af655fb0fab0492
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 <khali@linux-fr.org>
Documentation/i2c/chips/max6875
Documentation/i2c/writing-clients
drivers/i2c/busses/i2c-powermac.c
drivers/i2c/busses/i2c-viapro.c
drivers/i2c/busses/scx200_acb.c
drivers/i2c/chips/eeprom.c
drivers/i2c/chips/max6875.c
drivers/i2c/i2c-core.c
drivers/i2c/i2c-dev.c
drivers/macintosh/windfarm_smu_sat.c
include/linux/i2c.h