[U-Boot] [RFC] Make i2c probe opt-outable?

Tom Rini trini at ti.com
Fri May 18 20:43:19 CEST 2012


On 05/18/2012 11:26 AM, Wolfgang Denk wrote:
> Dear Tom Rini,
>
> In message<4FB674CD.8030502 at ti.com>  you wrote:
>>
>>    But still, the kernel decided i2c probing is dangerous/unreliable,
>> maybe we should follow, or at least allow boards to follow?
>
> The kernel is in a very different situation - it is supposed to run on
> perfect hardware.
>
> In U-Boot, we have to dead with green hardware that is in a completely
> unknown state, or with hardware that _might_ be broken in one way or
> another.  For us tools doing low-level accesses are invaluable - even
> if they include the risk to hang a system.

Right.  I'm not suggesting removing i2c probe, I'm just suggesting 
making it opt-out'able.  For example, on the beaglebone I can make i2c 
probe work as expected.  It's just requring that we toggle the I2C_CON 
enable bit for some reason in probe, but not when we are actually trying 
to write to a bad address.  I'd like to just #undef CONFIG_CMD_I2C_PROBE 
for the board and be done with it.  Otherwise it lists (nearly) every 
address which is useless.

-- 
Tom


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