--Allow multiple open iic fds by storing addressing state in cdevpriv
--Fix, as much as possible, the baked-in race conditions in the iic
ioctl interface by requesting bus ownership on I2CSTART, releasing it on
I2CSTOP/I2CRSTCARD, and requiring bus ownership by the current cdevpriv
to use the I/O ioctls
--Reduce internal iic buffer size and remove 1K read/write limit by
iteratively calling iicbus_read/iicbus_write
--Eliminate dynamic allocation in I2CWRITE/I2CREAD
--Move handling of I2CRDWR to separate function and improve error handling
--Add new I2CSADDR ioctl to store address in current cdevpriv so that
I2CSTART is not needed for read(2)/write(2) to work
--Redesign iicbus_request_bus() and iicbus_release_bus():
--iicbus_request_bus() no longer falls through if the bus is already
owned by the requesting device. Multiple threads on the same device may
want exclusive access. Also, iicbus_release_bus() was never
device-recursive anyway.
--Previously, if IICBUS_CALLBACK failed in iicbus_release_bus(), but
the following iicbus_poll() call succeeded, IICBUS_CALLBACK would not be
issued again
--Do not hold iicbus mtx during IICBUS_CALLBACK call. There are
several drivers that may sleep in IICBUS_CALLBACK, if IIC_WAIT is passed.
--Do not loop in iicbus_request_bus if IICBUS_CALLBACK returns
EWOULDBLOCK; instead pass that to the caller so that it can retry if so
desired.
Differential Revision: https://reviews.freebsd.org/D2140
Reviewed by: imp, jhb, loos
Approved by: kib (mentor)
forcing all transfers to do the start read/write stop by hand. Some
smart bridges prefer this sort of operation, and this allows us to
support their features more easily. When bridges don't support it, we
fall back to using the old-style opertaions. Expand the ioctl
interface to expose this function. Unlike the old-style interface,
this interface is thread safe, even on old bridges.
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)
