Hi,
I happened to take a look into drivers/w1 and found there bunch of thigs
that IMO should be changed:
- custom-made refcounting is racy
- lifetime rules need to be better enforced
- family framework is insufficient for many advanced w1 devices
- custom-made hotplug notification over netlink should be removed in favor
of standard hotplug notification
- sysfs attributes have unnecessary prefixes (like w1_master) or not needed
at all (w1_master_pointer)
Please consider series of patches below. Unfortunately I do not have any W1
equipment so it was only compile-tested. Please also note that lifetime and
locking rules were changed on object-by-object base so mid-series some stuff
may appear broken but as far as I can see the end result shoudl work pretty
well.
w1-whitespace.patch
Whitespace fixes.
w1-formatting.patch
Some formatting changes to bring the code in line with CodingStyle
guidelines.
w1-master-attr-group.patch
Use attribute_group to create master device attributes to guarantee
proper cleanup in case of failure. Also, hide most of attribute define
ugliness in macros.
w1-slave-attr-group.patc
Add 2 default attributes "family" and "serial" to slave devices, every
1-Wire slave has them. Use attribute_group to handle. The rest of slave
attributes are left as is - will be dealt with later.
w1-lists-cleanup.patch
List handling cleanup. Most of the list_for_each_safe users don't need
*_safe variant, *_entry variant is better suited in most places. Also,
checking retrieved list element for null is a bit pointless...
w1-drop-owner.patch
Drop owner field from w1_master and w1_slave structures. Just having it
there does not magically fixes lifetime rules.
w1-bus-ops.patch
Cleanup bus operations code:
- have bus operatiions accept w1_master instead of unsigned long and
drop data field from w1_bus_master so the structure can be statically
allocated by driver implementing it;
- rename w1_bus_master to w1_bus_ops to avoid confusion with w1_master;
- separate master registering and allocation so drivers can setup proper
link between private data and master and set useable master's name.
w1-fold-w1-int.patch
Fold w1_int.c into w1.c - there is no point in artificially separating
code for master devices between 2 files.
w1-drop-netlink.patch
Drop custom-made hotplug over netlink notification from w1 core.
Standard hotplug mechanism should work just fine (patch will follow).
w1-drop-control-thread.patch
Drop control thread from w1 core, whatever it does can also be done in
the context of w1_remove_master_device. Also, pin the module when
registering new master device to make sure that w1 core is not unloaded
until last device is gone. This simplifies logic a lot.
w1-move-search-to-io.patch
Move w1_search function to w1_io.c to be with the rest of IO code.
w1-master-drop-attrs.patch
Get rid of unneeded master device attributes:
- 'pointer' and 'attempts' are meaningless for userspace;
- information provided by 'slaves' and 'slave_count' can be gathered
from other sysfs bits;
- w1_slave_found has to be rearranged now that slave_count field is gone.
w1-master-attr-cleanup.patch
Clean-up master attribute implementation:
- drop unnecessary "w1_master" prefix from attribute names;
- do not acquire master->mutex when accessing attributes;
- move attribute code "closer" to the rest of master code.
w1-master-scan-interval.patch
More master attributes changes:
- rename timeout parameter/attribute to scan_interval to better
reflect its purpose;
- make scan_timeout be a per-device attribute and allow changing
it from userspace via sysfs;
- allow changing max_slave_count it from userspace as well.
w1-master-add-ttl-attr.patch
Add slave_ttl attribute to w1 masters.
w1-master-cleanup.patch
Clean-up master device implementation:
- get rid of separate refcount, rely on driver model to enforce
lifetime rules;
- use atomic to generate unique master IDs;
- drop unused fields.
w1-slave-cleanup.patch
Clean-up slave device implementation:
- get rid of separate refcount, rely on driver model to enforce
lifetime rules;
- pin w1 module until slave device is registered with sysfs to make
sure W1 core stays loaded.
- drop 'name' attribute as we already have it in bus_id.
w1-family-cleanup.patch
Clean-up family implementation:
- get rid of w1_family_ops and template attributes in w1_slave
structure and have family drivers create necessary attributes
themselves. There are too many different devices using 1-Wire
interface and it is impossible to fit them all into single
attribute model. If interface unification is needed it can be
done by building cross-bus class hierarchy.
- rename w1_smem to w1_sernum because devices are called Silicon
serial numbers, they have address (ID) but don't have memory
in regular sense.
- rename w1_therm to w1_thermal.
w1-family-is-driver.patch
Convert family into proper device-model drivers:
- embed driver structure into w1_family and register with the
driver core;
- do not try to manually bind slaves to familes, leave it to
the driver core;
- fold w1_family.c into w1.c
w1-device-id.patch
Support for automatic family drivers loading via hotplug:
- allow family drivers support list of families;
- export supported families through MODULE_DEVICE_TABLE.
w1-hotplug.patch
Implement W1 bus hotplug handler. Slave devices will define
FID=%02x (family ID) end SN=%024llX environment variables.
w1-module-attrs.patch
Allow changing w1 module parameters through sysfs, add parameter
descriptions and document them in Documentation/kernel-parameters.txt
Thanks!
--
Dmitry
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