Re: [PATCH] fix i810 i2c bug

On Mon, Jan 03, 2011 at 10:28:59AM +0100, Stefani Seibold wrote:

These patch fix a longstanding bug in the i810 frame buffer driver. 

The handling of the i2c bus is wrong: A 1 bit should not written to the
i2c, these will be done by switch the i2c to input. Driving an 1 bit
active is against the i2c spec.

An active driven of a 1 bit will result in very strange error, depending
which side is the more powerful one. In my case it depends on the
temperature of the Display-Controller-EEprom: With an cold eprom a got
the correct EDID datas, with a warm one some of the 1 bits was 0 :-(

The same bug is also in the intelfb driver in the file
drivers/video/intelfb/intelfb_i2c.c. The functions intelfb_gpio_setscl()
and intelfb_gpio_setsda() do drive the 1 bit active to the i2c bus. But
since i have no card which is used by the intelfb driver i cannot fix
it.

The patch is against linux next-20101231

- Stefani

Signed-off-by: Stefani Seibold <stefani@seibold.net>

Applied, thanks.

Also adding intelfb people to the Cc so they're aware of the problem, and
can follow suit.