Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Minor overhaul of SMBus support:
- Change smbus_callback() to pass a void * rather than caddr_t.
- Change smbus_bread() to pass a pointer to the count and have it be an
in/out parameter. The input is the size of the buffer (same as before),
but on return it will contain the actual amount of data read back from
the bus. Note that this value may be larger than the input value. It
is up to the caller to treat this as an error if desired.
- Change the SMB_BREAD ioctl to write out the updated struct smbcmd which
will contain the actual number of bytes read in the 'count' field. To
preserve the previous ABI, the old ioctl value is mapped to SMB_OLD_BREAD
which doesn't copy the updated smbcmd back out to userland. I doubt anyone
actually used the old BREAD anyway as it was rediculous to do a bulk-read
but not tell the using program how much data was actually read.
- Make the smbus driver and devclass public in the smbus module and
push all the DRIVER_MODULE()'s for attaching the smbus driver to
various foosmb drivers out into the foosmb modules. This makes all
the foosmb logic centralized and allows new foosmb modules to be
self-contained w/o having to hack smbus.c everytime a new smbus driver
is added.
- Add a new SMB_EINVAL error bit and use it in place of EINVAL to return
an error for bad arguments (such as invalid counts for bread and bwrite).
- Map SMB bus error bits to EIO in smbus_error().
- Make the smbus driver call bus_generic_probe() and require child drivers
such as smb(4) to create device_t's via identify routines. Previously,
smbus just created one anonymous device during attach, and if you had
multiple drivers that could attach it was just random chance as to which
driver got to probe for the sole device_t first.
- Add a mutex to the smbus(4) softc and use it in place of dummy splhigh()
to protect the 'owner' field and perform necessary synchronization for
smbus_request_bus() and smbus_release_bus().
- Change the bread() and bwrite() methods of alpm(4), amdpm(4), and
viapm(4) to only perform a single transaction and not try to use a
loop of multiple transactions for a large request. The framing and
commands to use for a large transaction depend on the upper-layer
protocol (such as SSIF for IPMI over SMBus) from what I can tell, and the
smb(4) driver never allowed bulk read/writes of more than 32-bytes
anyway. The other smb drivers only performed single transactions.
- Fix buffer overflows in the bread() methods of ichsmb(4), alpm(4),
amdpm(4), amdsmb(4), intpm(4), and nfsmb(4).
- Use SMB_xxx errors in viapm(4).
- Destroy ichsmb(4)'s mutex after bus_generic_detach() to avoid problems
from child devices making smb upcalls that would use the mutex during
their detach methods.

MFC after: 1 week
Reviewed by: jmg (mostly)

You wouldn't believe a driver could survive doing userland IO without
properly using copyin/copyout for more than 5 years? This one did. :-)

Properly encapsulate all user<->kernel data transfers using copy{in,out}.

MFC after: 1 month

$Id$ -> $FreeBSD$

Change /dev/smb and /dev/iic interface to allow user programs to interact with
devices dynamically. That means,

+ only one /dev/iic or /dev/smb device for each smb/iic bus to access
+ I2C/SMB device address must be given to any ioctl
+ new devices may be plugged and accessed after boot, which was
impossible previously (device addresses were hardcoded into
the kernel)

Reviewed by: Doug Rabson
Submitted by: nsouch
I2C and SMB ioctls