The recursive ownership support added in r321584 was unconditionally in
effect all the time -- whenever a given i2c slave device instance tried to
lock the i2c bus for exclusive use when it already owned the bus, the call
returned immediately without waiting. However, many i2c slave drivers use
bus ownership to enforce that only a single thread at a time can be using
the slave device. The recursive locking changes broke this use case.
Now there is a new flag, IIC_RECURSIVE, which can be mixed in with the
other flags passed to iicbus_acquire_bus() to allow drivers to indicate
when recursive locking is desired. Using the flag implies that the driver
is managing concurrent access to the device by different threads in some way.
This immediately fixes all existing i2c slave drivers except for the two
i2c RTC drivers which use the recursive locking feature; those will be
fixed in a followup commit.
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
on i2c devices, where the "register" can be any length.
Many (perhaps most) common i2c devices are organized as a collection of
(usually 1-byte-wide) registers, and are accessed by first writing a 1-byte
register index/offset number, then by reading or writing the data.
Generally there is an auto-increment feature so the when multiple bytes
are read or written, multiple contiguous registers are accessed.
Most existing slave device drivers allocate an array of iic_msg structures,
fill in all the transfer info, and invoke iicbus_transfer(). These new
functions commonize all that and reduce register access to a simple call
with a few arguments.
while holding exclusive ownership of the bus. This is the routine most
slave drivers should use unless they have a need to acquire and hold the
bus across a series of related operations that involves multiple transfers.
these functions are thin wrappers around calling the hardware-layer driver,
but some of them do sanity checks and return an error. Since the hardware
layer can only return IIC_Exxxxx status values, the iicbus helper functions
must also adhere to that, so that drivers at higher layers can assume that
any non-zero status value is an IIC_Exxxx value that provides details about
what happened at the hardware layer (sometimes those details are important
for certain slave drivers).
errno values that are at least vaguely equivelent. Also add a new status
value, IIC_ERESOURCE, to indicate a failure to acquire memory or other
required resources to complete a transaction.
The IIC_Exxxxxx values are supposed to communicate low-level details of the
i2c transaction status between the lowest-layer hardware driver and
higher-layer bus protocol and device drivers for slave devices on the bus.
Most of those slave drivers just return all status values from the lower
layers directly to their callers, resulting in crazy error reporting from a
user's point of view (things like timeouts being reported as "no such
process"). Now there's a helper function to make it easier to start
cleaning up all those drivers.
Make it clearer what each one means in the comments that define them.
IIC_BUSBSY was used in many places to mean two different things, either
"someone else has reserved the bus so you have to wait until they're done"
or "the signal level on the bus was not in the state I expected before/after
issuing some command".
Now IIC_BUSERR is used consistantly to refer to protocol/signaling errors,
and IIC_BUSBSY refers to ownership/reservation of the bus.
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.
drivers that implemnt the i2c bit banging bus interface not have to
recompile iicbb in order to add an attachment for it.
This will mean the bktr and other definitions can go back to their
respective drivers.
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)
