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authorLen Brown <len.brown@intel.com>2008-10-22 23:57:26 -0400
committerLen Brown <len.brown@intel.com>2008-10-23 00:11:07 -0400
commit057316cc6a5b521b332a1d7ccc871cd60c904c74 (patch)
tree4333e608da237c73ff69b10878025cca96dcb4c8 /Documentation/w1
parent3e2dab9a1c2deb03c311eb3f83466009147ed4d3 (diff)
parent2515ddc6db8eb49a79f0fe5e67ff09ac7c81eab4 (diff)
Merge branch 'linus' into test
Conflicts: MAINTAINERS arch/x86/kernel/acpi/boot.c arch/x86/kernel/acpi/sleep.c drivers/acpi/Kconfig drivers/pnp/Makefile drivers/pnp/quirks.c Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/w1')
-rw-r--r--Documentation/w1/00-INDEX2
-rw-r--r--Documentation/w1/masters/ds249052
-rw-r--r--Documentation/w1/slaves/00-INDEX4
-rw-r--r--Documentation/w1/slaves/w1_therm41
-rw-r--r--Documentation/w1/w1.generic11
5 files changed, 109 insertions, 1 deletions
diff --git a/Documentation/w1/00-INDEX b/Documentation/w1/00-INDEX
index 5270cf4cb10..cb49802745d 100644
--- a/Documentation/w1/00-INDEX
+++ b/Documentation/w1/00-INDEX
@@ -1,5 +1,7 @@
00-INDEX
- This file
+slaves/
+ - Drivers that provide support for specific family codes.
masters/
- Individual chips providing 1-wire busses.
w1.generic
diff --git a/Documentation/w1/masters/ds2490 b/Documentation/w1/masters/ds2490
index 239f9ae0184..28176def3d6 100644
--- a/Documentation/w1/masters/ds2490
+++ b/Documentation/w1/masters/ds2490
@@ -16,3 +16,55 @@ which allows to build USB <-> W1 bridges.
DS9490(R) is a USB <-> W1 bus master device
which has 0x81 family ID integrated chip and DS2490
low-level operational chip.
+
+Notes and limitations.
+- The weak pullup current is a minimum of 0.9mA and maximum of 6.0mA.
+- The 5V strong pullup is supported with a minimum of 5.9mA and a
+ maximum of 30.4 mA. (From DS2490.pdf)
+- While the ds2490 supports a hardware search the code doesn't take
+ advantage of it (in tested case it only returned first device).
+- The hardware will detect when devices are attached to the bus on the
+ next bus (reset?) operation, however only a message is printed as
+ the core w1 code doesn't make use of the information. Connecting
+ one device tends to give multiple new device notifications.
+- The number of USB bus transactions could be reduced if w1_reset_send
+ was added to the API. The name is just a suggestion. It would take
+ a write buffer and a read buffer (along with sizes) as arguments.
+ The ds2490 block I/O command supports reset, write buffer, read
+ buffer, and strong pullup all in one command, instead of the current
+ 1 reset bus, 2 write the match rom command and slave rom id, 3 block
+ write and read data. The write buffer needs to have the match rom
+ command and slave rom id prepended to the front of the requested
+ write buffer, both of which are known to the driver.
+- The hardware supports normal, flexible, and overdrive bus
+ communication speeds, but only the normal is supported.
+- The registered w1_bus_master functions don't define error
+ conditions. If a bus search is in progress and the ds2490 is
+ removed it can produce a good amount of error output before the bus
+ search finishes.
+- The hardware supports detecting some error conditions, such as
+ short, alarming presence on reset, and no presence on reset, but the
+ driver doesn't query those values.
+- The ds2490 specification doesn't cover short bulk in reads in
+ detail, but my observation is if fewer bytes are requested than are
+ available, the bulk read will return an error and the hardware will
+ clear the entire bulk in buffer. It would be possible to read the
+ maximum buffer size to not run into this error condition, only extra
+ bytes in the buffer is a logic error in the driver. The code should
+ should match reads and writes as well as data sizes. Reads and
+ writes are serialized and the status verifies that the chip is idle
+ (and data is available) before the read is executed, so it should
+ not happen.
+- Running x86_64 2.6.24 UHCI under qemu 0.9.0 under x86_64 2.6.22-rc6
+ with a OHCI controller, ds2490 running in the guest would operate
+ normally the first time the module was loaded after qemu attached
+ the ds2490 hardware, but if the module was unloaded, then reloaded
+ most of the time one of the bulk out or in, and usually the bulk in
+ would fail. qemu sets a 50ms timeout and the bulk in would timeout
+ even when the status shows data available. A bulk out write would
+ show a successful completion, but the ds2490 status register would
+ show 0 bytes written. Detaching qemu from the ds2490 hardware and
+ reattaching would clear the problem. usbmon output in the guest and
+ host did not explain the problem. My guess is a bug in either qemu
+ or the host OS and more likely the host OS.
+-- 03-06-2008 David Fries <David@Fries.net>
diff --git a/Documentation/w1/slaves/00-INDEX b/Documentation/w1/slaves/00-INDEX
new file mode 100644
index 00000000000..f8101d6b07b
--- /dev/null
+++ b/Documentation/w1/slaves/00-INDEX
@@ -0,0 +1,4 @@
+00-INDEX
+ - This file
+w1_therm
+ - The Maxim/Dallas Semiconductor ds18*20 temperature sensor.
diff --git a/Documentation/w1/slaves/w1_therm b/Documentation/w1/slaves/w1_therm
new file mode 100644
index 00000000000..0403aaaba87
--- /dev/null
+++ b/Documentation/w1/slaves/w1_therm
@@ -0,0 +1,41 @@
+Kernel driver w1_therm
+====================
+
+Supported chips:
+ * Maxim ds18*20 based temperature sensors.
+
+Author: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
+
+
+Description
+-----------
+
+w1_therm provides basic temperature conversion for ds18*20 devices.
+supported family codes:
+W1_THERM_DS18S20 0x10
+W1_THERM_DS1822 0x22
+W1_THERM_DS18B20 0x28
+
+Support is provided through the sysfs w1_slave file. Each open and
+read sequence will initiate a temperature conversion then provide two
+lines of ASCII output. The first line contains the nine hex bytes
+read along with a calculated crc value and YES or NO if it matched.
+If the crc matched the returned values are retained. The second line
+displays the retained values along with a temperature in millidegrees
+Centigrade after t=.
+
+Parasite powered devices are limited to one slave performing a
+temperature conversion at a time. If none of the devices are parasite
+powered it would be possible to convert all the devices at the same
+time and then go back to read individual sensors. That isn't
+currently supported. The driver also doesn't support reduced
+precision (which would also reduce the conversion time).
+
+The module parameter strong_pullup can be set to 0 to disable the
+strong pullup or 1 to enable. If enabled the 5V strong pullup will be
+enabled when the conversion is taking place provided the master driver
+must support the strong pullup (or it falls back to a pullup
+resistor). The DS18b20 temperature sensor specification lists a
+maximum current draw of 1.5mA and that a 5k pullup resistor is not
+sufficient. The strong pullup is designed to provide the additional
+current required.
diff --git a/Documentation/w1/w1.generic b/Documentation/w1/w1.generic
index 4c6509dd478..e3333eec432 100644
--- a/Documentation/w1/w1.generic
+++ b/Documentation/w1/w1.generic
@@ -79,10 +79,13 @@ w1 master sysfs interface
<xx-xxxxxxxxxxxxx> - a directory for a found device. The format is family-serial
bus - (standard) symlink to the w1 bus
driver - (standard) symlink to the w1 driver
+w1_master_add - Manually register a slave device
w1_master_attempts - the number of times a search was attempted
w1_master_max_slave_count
- the maximum slaves that may be attached to a master
w1_master_name - the name of the device (w1_bus_masterX)
+w1_master_pullup - 5V strong pullup 0 enabled, 1 disabled
+w1_master_remove - Manually remove a slave device
w1_master_search - the number of searches left to do, -1=continual (default)
w1_master_slave_count
- the number of slaves found
@@ -90,7 +93,13 @@ w1_master_slaves - the names of the slaves, one per line
w1_master_timeout - the delay in seconds between searches
If you have a w1 bus that never changes (you don't add or remove devices),
-you can set w1_master_search to a positive value to disable searches.
+you can set the module parameter search_count to a small positive number
+for an initially small number of bus searches. Alternatively it could be
+set to zero, then manually add the slave device serial numbers by
+w1_master_add device file. The w1_master_add and w1_master_remove files
+generally only make sense when searching is disabled, as a search will
+redetect manually removed devices that are present and timeout manually
+added devices that aren't on the bus.
w1 slave sysfs interface