Re: [lm-sensors] [RFC] (almost) booting allyesconfig -- please don't poke super-io without request_region

On Jul 10, 2008, at 4:33 PM, Hans de Goede wrote:

Milton Miller wrote:

quoted

After the following patch to mark the isa region busy and applying a 
few
patches[1], I was able to kexec boot into an all-yes-config kernel 
from linux-next, with the following KCONFIG_ALLCONFIG file:

...

quoted

While the first two might not be required, and the third is just
selecting the right platform, it would be nice to get the drivers
to play as well as the rest of the kernel.
The drivers all are for super-io chips, either irda/FIR drivers or 
hwmon,
and poke at isa ports without checking request_region.

Erm,

The superio sensor drivers only poke the superio chip registers 
without request region during the probe phase, iow they try to detect 
the chip, using a widely document and standardized (part of isa pnp 
AFAIK) procedure on standardized ports.

Let me try to explain a bit about superio chips, they have 2 superio 
control registers (an index and data register) with which things like 
a manufacturer and device id can be read, besides these id registers 
they also have a set of registers with config for different logical 
devices. Once the id is matched, the driver knows which logical device 
config to read, reads a (different) isa base address + range from the 
logical device config, and then does a request_region on the region 
actually used by the logical device.

The superio control registers are thus a sort of pci configuration 
space if you want, doing a request_region on these is not such a good 
idea, as multiple drivers (for different logical devices within the 
superio device) may use these, so trying to gain exclusive access will 
lead to troubles.

I hope with this info about the problem space, that you maybe have a 
suggestion on howto fix this?

My point is that they are probing without even knowing that a such a IO 
range exists.

These are the only drivers left in the tree that still do this.  (At 
least that are not
blocked on a powerpc allyesconfig for 64-bit, !CONFIG_VIRT_TO_BUS).

One could make a superio driver, and create sub-devices for the IR, 
I2C, floppy, parallel, etc
nodes.

I would even accept a check_region (horrors!), it would impove the 
situation.

But most other drivers do this by request_region, probe, then release 
the region afterwards.

Besides, one could argue the superio region should be requested while 
probing, to prevent other cpus from poking at the super io chip at the 
same time.   Think of it as missing locking.

milton