De-activating this reading back will effectively half the time required
for a write to the output register.
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The 'mutex' in struct w1_master is use for two very different
purposes.
Firstly it protects various data structures such as the list of all
slaves.
Secondly it protects the w1 buss against concurrent accesses.
This can lead to deadlocks when the ->probe code called while adding a
slave needs to talk on the bus, as is the case for power_supply
devices.
ds2780 and ds2781 drivers contain a work around to track which
process hold the lock simply to avoid this deadlock. bq27000 doesn't
have that work around and so deadlocks.
There are other possible deadlocks involving sysfs.
When removing a device the sysfs s_active lock is held, so the lock
that protects the slave list must take precedence over s_active.
However when access power_supply attributes via sysfs, the s_active
lock must take precedence over the lock that protects accesses to
the bus.
So to avoid deadlocks between w1 slaves and sysfs, these must be
two separate locks. Making them separate means that the work around
in ds2780 and ds2781 can be removed.
So this patch:
- adds a new mutex: "bus_mutex" which serialises access to the bus.
- takes in mutex in w1_search and ds1wm_search while they access
the bus for searching. The mutex is dropped before calling the
callback which adds the slave.
- changes all slaves to use bus_mutex instead of mutex to
protect access to the bus
- removes w1_ds2790_io_nolock and w1_ds2781_io_nolock, and the
related code from drivers/power/ds278[01]_battery.c which
calls them.
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
NULL not 0 should be used with pointers. Just remove the offending
lines since they will default to NULL anyway.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The for loop was looking for i <= 0 instead of i >= 0 so this function
never did anything. Also we started with i = NB_SYSFS_BIN_FILES instead
of "NB_SYSFS_BIN_FILES - 1" which is an off by one bug.
Reported-by: Bojan Prtvar <prtvar.b@gmail.com>
Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Jean-Franois Dagenais <dagenaisj@sonatest.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This DS2408 w1 slave driver is not complete for all the features of the
chip, but its sufficient if you use it as a simple IO expander.
[randy.dunlap@oracle.com: fix w1_ds2408.c printk formats]
Signed-off-by: Jean-François Dagenais <dagenaisj@sonatest.com>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
Cc: Matt Reimer <mreimer@vpop.net>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Jean-Francois Dagenais