These realtek switch PHYs speak a variant of i2c with some slightly
modified handling.
From the submitter, slightly modified now that some further digging
has been done:
The I2C framework makes a assumption that the read/not-write bit of the first
byte (the address) indicates whether reads or writes are to follow.
The RTL8366 family uses the bus: after sending the address+read/not-write byte,
two register address bytes are sent, then the 16-bit register value is sent
or received. While the register write access can be performed as a 4-byte
write, the read access requires the read bit to be set, but the first two bytes
for the register address then need to be transmitted.
This patch maintains the i2c protocol behaviour but allows it to be relaxed
(for these kinds of switch PHYs, and whatever else Realtek may do with this
almost-but-not-quite i2c bus) - by setting the "strict" hint to 0.
The "strict" hint defaults to 1.
Submitted by: Stefan Bethke <stb@lassitu.de>
- Add an sx lock to the iic(4) driver to serialize open(), close(), read(),
and write and to protect sc_addr and sc_count in the softc.
- Use cdev->si_drv1 instead of using the minor number of the cdev to
lookup the softc via newbus in iic(4).
- Store the device_t in the softc to avoid a similar detour via minor
numbers in iic(4).
- Only add at most one instance of iic(4) and iicsmb(4) to each iicbus(4)
instance, and do it in the child driver.
- Add a mutex to the iicbus(4) softc to synchronize the request/release bus
stuff.
- Use __BUS_ACCESSOR() for IICBUS_ACCESSOR() instead of rolling our own.
- Add a mutex to the iicsmb(4) softc to protect softc state updated in the
interrupt handler.
- Remove Giant from all the smbus methods in iicsmb(4) now that all the
iicbus(4) backend is locked.
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)
