[lm-sensors] I2C_PCA_ISA causes boot delays (was re: sis96x compiled in by error: delay of one minute at boot)
etienne_lorrain at yahoo.fr
Wed Mar 29 11:26:28 CEST 2006
--- "Mark M. Hoffman" <mhoffman at lightlink.com> wrote:
> > 885c885
> > < # CONFIG_I2C_PCA_ISA is not set
> > ---
> > > CONFIG_I2C_PCA_ISA=y
> This alone is the cause of the delay. (I have confirmed it by running some
> similar .configs here.) You almost certainly don't own this specialized
> piece of hardware. Worse still, that particular driver has no code to detect
> whether or not the hardware is present. I cc'ed the listed driver author
> (Ian) just in case this might be corrected... but I guess there is no way
> to fix it.
> So the delay is (1) an I2C bus driver that is not actually present, trying to
> probe for (2) seven different sensors chip drivers that certainly aren't present
> on the nonexistent bus. Timeouts ensue.
> So unless Ian knows a better way to detect that bus driver... the best I can
> advise is to *not* build in those drivers for hardware that you do not have.
OK, I know the I2C protocol, and I can imagine a hardware board which does
not have a way to detect its own presence - or the presence of its own ISA bus.
What I dislike the most is that, after the driver has taken more than 20
seconds to probe something it did not find, it did not display anything to
say "either there is a hardware problem, or you should disable me".
Are you sure that there isn't any distribution around trying to insert
_all_ the modules to do hardware detection?
Note that most I2C driver detect abscence of the hardware in a lot less than
a second: most of the I2C system is fine.
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