linux-toradex.git/drivers/w1/w1.h, branch v3.12.2

W1: split master mutex to avoid deadlocks.

2012-06-13T23:38:40+00:00

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 
Acked-by: Evgeniy Polyakov 
Signed-off-by: Greg Kroah-Hartman

Revert "w1: introduce a slave mutex for serializing IO"

2012-06-13T23:33:54+00:00

This reverts commit 59d4467be405316916a4087d5b02d99196eeef04.

Turns out it was the wrong version, will apply the correct version after
this.

Reported-by: NeilBrown 
Cc: Evgeniy Polyakov 
Cc: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

w1: introduce a slave mutex for serializing IO

2012-06-12T22:27:32+00:00

w1 devices need a mutex to serial IO.  Most use master->mutex.
However that is used for other purposes and they can conflict.

In particular master->mutex is held while w1_attach_slave_device is
called.

For bq27000, this registers a 'powersupply' device which tries to read the
current status.  The attempt to read will cause a deadlock on
master->mutex.

So create a new per-slave mutex and use that for serializing IO for
bq27000.

Signed-off-by: NeilBrown 
Cc: Evgeniy Polyakov 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

MAINTAINERS: Evgeniy has moved

2011-08-25T23:25:33+00:00

Signed-off-by: Evgeniy Polyakov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

w1: have netlink search update kernel list

2011-05-27T00:12:38+00:00

Reorganize so the netlink connector one wire search command will update
the kernel list of detected slave devices.  Otherwise, a newly detected
device is unusable because unless it's in the kernel list of known devices
any commands will result in ENODEV status.

Signed-off-by: David Fries 
Cc: Evgeniy Polyakov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

w1: add 1-wire (w1) reset and resume command API support

2011-05-27T00:12:38+00:00

The first patch adds generic functionnality to w1_io for Resume Command
[A5h] lots of slaves support.  I found it useful for multi-commands/reset
workflows with the same slave on a multi-slave bus.

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.  Enjoy!

The ds1wm had Kconfig dependencies towards ARM && HAVE_CLK.  I took them
out since I was using the ds1wm on an x86_64 platform (ds1wm in a FPGA
through pcie) and found them irrelevant.

The clock freq/divisors at the top of ds1wm.c did not have the MSB set to
1.  This bit is CLK_EN which turns the whole prescaler and dividers on.
The driver never mentionned this bit either, so I just included this bit
right in the table entries.  I also took the liberty to add a couple of
entries to the table.  The spec doesn't explicitely mentions these
possibilities but the description and examination of the core shows the
prescalers & dividers can be used for more than the table explicitely
shows.  The table I enlarged still doesn't cover all possibilities, but
it's a good start.

I also made a few tweaks to a couple of the read and write algorithms
which made sense while I had my head very deep in the ds1wm documentation.
 We stressed it a lot with 10+ slaves on the bus, many ds2408, ds2431 and
ds2433 at the same time doing extensive interaction.  It proved quite
stable in our production environment.

This patch:

Add generic functionnality to w1_io for Resume Command [A5h] lots of
slaves support.

Signed-off-by: Jean-François Dagenais 
Cc: Evgeniy Polyakov 
Cc: Szabolcs Gyurko 
Cc: Matt Reimer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

w1: add touch block command

2009-01-08T16:31:13+00:00

Writes and returns sampled data back to userspace.

Signed-off-by: Evgeniy Polyakov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

w1: export w1_read_8 function

2008-11-13T01:17:18+00:00

Export the w1_read_8 function for use of drivers.  The OMAP HDQ
driver(drivers/w1/masters/omap_hdq.c) uses this function.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Madhusudhan Chikkature
Acked-by: Evgeniy Polyakov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

W1: w1_therm fix user buffer overflow and cat

2008-10-16T18:21:50+00:00

Fixed data reading bug by replacing binary attribute with device one.

Switching the sysfs read from bin_attribute to device_attribute.  The data
is far under PAGE_SIZE so the binary interface isn't required.  As the
device_attribute interface will make one call to w1_therm_read per file
open and buffer, the result is, the following problems go away.

buffer overflow:
	Execute a short read on w1_slave and w1_therm_read_bin would still
	return the full string size worth of data clobbering the user space
	buffer when it returned.  Switching to device_attribute avoids the
	buffer overflow problems.  With the snprintf formatted output dealing
	with short reads without doing a conversion per read would have
	been difficult.
bad behavior:
	`cat w1_slave` would cause two temperature conversions to take place.
	Previously the code assumed W1_SLAVE_DATA_SIZE would be returned with
	each read.  It would not return 0 unless the offset was less
	than W1_SLAVE_DATA_SIZE.  The result was the first read did a
	temperature conversion, filled the buffer and returned, the
	offset in the second read would be less than
	W1_SLAVE_DATA_SIZE and also fill the buffer and return, the
	third read would finnally have a big enough offset to return 0
	and cause cat to stop.  Now w1_therm_read will be called at
	most once per open.

Signed-off-by: David Fries 
Signed-off-by: Evgeniy Polyakov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

W1: feature, enable hardware strong pullup

2008-10-16T18:21:49+00:00

Add a strong pullup option to the w1 system.  This supplies extra power
for parasite powered devices.  There is a w1_master_pullup sysfs entry and
enable_pullup module parameter to enable or disable the strong pullup.

The one wire bus requires at a minimum one wire and ground.  The common
wire is used for sending and receiving data as well as supplying power to
devices that are parasite powered of which temperature sensors can be one
example.  The bus must be idle and left high while a temperature
conversion is in progress, in addition the normal pullup resister on
larger networks or even higher temperatures might not supply enough power.
 The pullup resister can't provide too much pullup current, because
devices need to pull the bus down to write a value.  This enables the
strong pullup for supported hardware, which can supply more current when
requested.  Unsupported hardware will just delay with the bus high.

The hardware USB 2490 one wire bus master has a bit on some commands which
will enable the strong pullup as soon as the command finishes executing.
To use strong pullup, call the new w1_next_pullup function to register the
duration.  The next write command will call set_pullup before sending the
data, and reset the duration to zero once it returns.

Switched from simple_strtol to strict_strtol.

Signed-off-by: David Fries 
Cc: Evgeniy Polyakov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds