On Wed, Feb 24, 2016 at 08:19:58AM +0100, Jiri Pirko wrote: > Tue, Feb 23, 2016 at 10:19:48PM CET, [email protected] wrote: > >On Tue, Feb 23, 2016 at 04:51:26PM +0100, Jiri Pirko wrote: > >> From: Jiri Pirko <[email protected]> > >> > >> Introduce devlink infrastructure for drivers to register and expose to > >> userspace via generic Netlink interface. > >> > >> There are two basic objects defined: > >> devlink - one instance for every "parent device", for example switch ASIC > >> devlink port - one instance for every physical port of the device. > >> > >> This initial portion implements basic get/dump of objects to userspace. > >> Also, port splitter and port type setting is implemented. > >... > >> +/** > >> + * devlink_alloc - Allocate new devlink instance resources > >> + * > >> + * @ops: ops > >> + * @priv_size: size of user private data > >> + * > >> + * Allocate new devlink instance resources, including devlink index > >> + * and name. > >> + */ > >> +struct devlink *devlink_alloc(const struct devlink_ops *ops, size_t > >> priv_size) > >> +{ > >> + static atomic_t dev_counter = ATOMIC_INIT(0); > >> + struct devlink *devlink; > >> + > >> + devlink = kzalloc(sizeof(*devlink) + priv_size, GFP_KERNEL); > >> + if (!devlink) > >> + return NULL; > >> + devlink->ops = ops; > >> + devlink_net_set(devlink, &init_net); > >> + > >> +different_name: > >> + devlink->index = atomic_inc_return(&dev_counter); > >> + if (devlink->index < 0) { > >> + /* wrapped */ > >> + atomic_dec(&dev_counter); > >> + kfree(devlink); > >> + return NULL; > >> + } > >> + /* atomic_inc_return makes it start at 1, make it start at 0 */ > >> + devlink->index--; > >> + > >> + dev_set_name(&devlink->dev, DEVLINK_GENL_NAME "%d", devlink->index); > >> + if (devlink_name_exists(devlink_net(devlink), devlink_name(devlink))) > >> + goto different_name; > >> + > >> + INIT_LIST_HEAD(&devlink->port_list); > >> + device_initialize(&devlink->dev); > >> + devlink->dev.class = &devlink_class; > >> + devlink->dev.platform_data = devlink; > >> + return devlink; > >> +} > >> +EXPORT_SYMBOL_GPL(devlink_alloc); > > > >The increment then decrement bit feels... Clunky and a little confusing. > >Why not just atomic_read(&dev_counter) before different_name:, then an > >atomic_inc_return(&dev_counter) under the if clause before the goto, and > >eliminate the devlink->index-- bit? > > If I split it it would not be atomic op anymore. But the > devlink->index-- is just to adjust the start, nothing else. > This is copied from nl80211 code.
Argh, I'm a moron. You need to increment dev_counter, can't just read it's current value. Still fugly, but okay, does actually serve a purpose this way. -- Jarod Wilson [email protected]
