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Restore the ability for i2c slave devices to do IO from their probe method.

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r348164 added code to iicbus_request_bus/iicbus_release_bus to automatically
call device_busy()/device_unbusy() as part of aquiring exclusive use of the
bus (so modules can't be unloaded while the bus is exclusively owned and/or
IO is in progress).  That broke the ability to do i2c IO from a slave device
probe method, because the slave isn't attached yet, so calling device_busy()
triggers a sanity-check panic for trying to busy a non-attached device.

Now we check whether the device status is < DS_ATTACHING, and if so we busy
the iicbus rather than the slave device.  I think this leaves a small window
where a module could be unloaded while probing is in progress.  But I think
that's true of all devices, and probably should be fixed by introducing a
DS_PROBING state for devices, and handling that at various points in the
newbus code.
This commit is contained in:
Ian Lepore 2019-07-08 20:26:56 +00:00
parent 8fe7bf064f
commit 873bf31b2b
2 changed files with 11 additions and 4 deletions
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1
sys/dev/iicbus/iicbus.h
View File

@ -41,6 +41,7 @@ struct iicbus_softc
{
device_t dev; /* Myself */
device_t owner; /* iicbus owner device structure */
device_t busydev; /* iicbus_release_bus calls unbusy on this */
u_int owncount; /* iicbus ownership nesting count */
u_char started; /* address of the 'started' slave
* 0 if no start condition succeeded */

14
sys/dev/iicbus/iiconf.c
View File

@ -131,9 +131,15 @@ iicbus_request_bus(device_t bus, device_t dev, int how)
/*
* Mark the device busy while it owns the bus, to
* prevent detaching the device, bus, or hardware
* controller, until ownership is relinquished.
* controller, until ownership is relinquished. If the
* device is doing IO from its probe method before
* attaching, it cannot be busied; mark the bus busy.
*/
device_busy(dev);
if (device_get_state(dev) < DS_ATTACHING)
sc->busydev = bus;
else
sc->busydev = dev;
device_busy(sc->busydev);
/*
* Drop the lock around the call to the bus driver, it
* should be allowed to sleep in the IIC_WAIT case.
@ -150,7 +156,7 @@ iicbus_request_bus(device_t bus, device_t dev, int how)
sc->owner = NULL;
sc->owncount = 0;
wakeup_one(sc);
device_unbusy(dev);
device_unbusy(sc->busydev);
}
}
}
@ -184,7 +190,7 @@ iicbus_release_bus(device_t bus, device_t dev)
IICBUS_LOCK(sc);
sc->owner = NULL;
wakeup_one(sc);
device_unbusy(dev);
device_unbusy(sc->busydev);
}
IICBUS_UNLOCK(sc);
return (0);