linux-kernel - Re: [PATCH 1/3] ifb: make device count build-time configurable

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Date:	Tue, 12 Jan 2016 16:19:58 +0100
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Lubomir Rintel <lkundrak@...sk>
CC:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH 1/3] ifb: make device count build-time configurable

On 01/12/2016 12:56 PM, Lubomir Rintel wrote:
> 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
> compatibility.
>
> Let's do that here as well.

Thanks for the set in general, good to see it fixed!

> Signed-off-by: Lubomir Rintel <lkundrak@...sk>
> ---
[...]
> +config IFB_COUNT
> +        int "Number of ifb devices to pre-create at init time"
> +        depends on IFB
> +        default 3

Should that not be 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.

[...]
> -static int numifbs = 2;
               ^^^^^^^^^^^^
> +static int numifbs = CONFIG_IFB_COUNT;
>   module_param(numifbs, int, 0);
>   MODULE_PARM_DESC(numifbs, "Number of ifb devices");