[PATCH v2] ifb: make device count build-time configurable

From: Lubomir Rintel
Date: Tue Jan 12 2016 - 10:37:08 EST

The devices can be created at run-time for quite some time already and the
load-time device creation collides with attempts to create the device of
the same name:

# rmmod ifb
# ip link add ifb0 type ifb
RTNETLINK answers: File exists

This is pretty much the same situation as was with the block loop devices
which was solved by adding a build-time configuration that the
distributions could use as they deem fit while keeping the default for

Let's do that here as well.

Signed-off-by: Lubomir Rintel <lkundrak@xxxxx>
Changes since v1:
- The default number of devices is 2 not 3.

drivers/net/Kconfig | 21 +++++++++++++++++----
drivers/net/ifb.c | 2 +-
2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index f184fb5..bb40d30 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -110,12 +110,25 @@ config IFB
This is an intermediate driver that allows sharing of
To compile this driver as a module, choose M here: the module
- will be called ifb. If you want to use more than one ifb
- device at a time, you need to compile this driver as a module.
- Instead of 'ifb', the devices will then be called 'ifb0',
- 'ifb1' etc.
+ will be called ifb.
Look at the iproute2 documentation directory for usage etc

+config IFB_COUNT
+ int "Number of ifb devices to pre-create at init time"
+ depends on IFB
+ default 2
+ help
+ Static number of ifb devices to be unconditionally pre-created
+ at init time.
+ This default value can be overwritten on the kernel command
+ line or with module-parameter ifb.numifbs.
+ The historic default is 3. If a mid-2007 version of iproute2
+ is used (v2.6.23 or later), it can be set to 0, since needed
+ ifb devices can be dynamically allocated via rtnetlink.
source "drivers/net/team/Kconfig"

config MACVLAN
diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index cc56fac..911af2c 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -298,7 +298,7 @@ static struct rtnl_link_ops ifb_link_ops __read_mostly = {
* Note that these legacy devices have one queue.
* Prefer something like : ip link add ifb10 numtxqueues 8 type ifb
-static int numifbs = 2;
+static int numifbs = CONFIG_IFB_COUNT;
module_param(numifbs, int, 0);
MODULE_PARM_DESC(numifbs, "Number of ifb devices");