linux-kernel - Re: getting configuration info into a driver at load-time

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Date:	Tue, 28 Oct 2008 23:14:25 +0100
From:	"Kay Sievers" <kay.sievers@...y.org>
To:	"Sebastian Kuzminsky" <seb@...hlab.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: getting configuration info into a driver at load-time

On Tue, Oct 28, 2008 at 00:07, Sebastian Kuzminsky <seb@...hlab.com> wrote:
> Hi folks, i'm looking for a way to pass structured configuration information
> to a device driver at load-time.
>
> I'm working on a device driver for a family of FPGA cards for motion control
> of industrial robots and computer-controlled machine tools.  The driver
> loads the FPGA firmware with request_firmware() and sends it to the FPGA.
>
> Once the FPGA is up and running, the user needs to configure the firmware
> specifically for their machine, by telling the firmware things like "my
> machine has two stepper motors and three servo motors, and the second servo
> motor has an encoder with an index channel".  The details of the information
> being relayed isnt important, the key thing is that it's like a struct
> containing a couple of arrays of different kinds structs, something like
> this:
>
>    struct config {
>
>        struct {
>            bool enabled;
>            bool index_enabled;
>            bool index_mask_enabled;
>        } encoder_config[];
>
>        struct {
>            bool enabled;
>        } pwmgen_config[];
>
>        struct {
>            bool enabled;
>            uint width;
>        } stepgen_config[];
>
>        char *firmware;
>
>        bool enable_raw;
>
>    } board_config;
>
>
> Each board that the driver finds should get its own "board_config".
>
> I thought about exposing this config structure in /sys or /proc (in a
> per-board directory), and let the user poke in the config values after the
> driver has loaded, but I'd really prefer to make the information available
> at load-time.
>
> Currently the driver has a module param array of char*, with each board's
> configuration encoded into an ascii string which gets decoded "by hand" in
> the driver.  Pretty grotty.
>
> Is there some easier/cleaner way to do this?

Maybe configfs?

Kay
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