[PATCH v2] drm/pl111: Fix module probe bug

[seanpaul@chromium.org (Sean Paul)]

On Thu, May 03, 2018 at 04:04:31PM +0200, Linus Walleij wrote:
> Commit a30933c27602 ("drm/pl111: Support the Versatile Express")
> Added a second module using the builtin_platform_driver() call,
> which works fine as long as you do not try to build the PL111
> driver as a module, because a module can only have one initcall
> and cause the following build bug:
> 
> (...) multiple definition of `init_module' (...)
> 
> Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Liviu Dudau <liviu.dudau@arm.com>
> Cc: Pawel Moll <pawel.moll@arm.com>
> Cc: Eric Anholt <eric@anholt.net>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Fixes: a30933c27602 ("drm/pl111: Support the Versatile Express")
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v1->v2:
> - In my stress I missed that if there are several CLCD instances
>   on the board the platform_driver_register() call will return
>   -EBUSY so we need to ignore that explicitly, all we want is to
>   register the driver at least once.
> ---
>  drivers/gpu/drm/pl111/pl111_versatile.c |  7 +++++++
>  drivers/gpu/drm/pl111/pl111_vexpress.c  | 12 ++++++++++--
>  drivers/gpu/drm/pl111/pl111_vexpress.h  |  7 +++++++
>  3 files changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/pl111/pl111_versatile.c b/drivers/gpu/drm/pl111/pl111_versatile.c
> index 78ddf8534fd2..ad769e3e9fd3 100644
> --- a/drivers/gpu/drm/pl111/pl111_versatile.c
> +++ b/drivers/gpu/drm/pl111/pl111_versatile.c
> @@ -326,6 +326,13 @@ int pl111_versatile_init(struct device *dev, struct pl111_drm_dev_private *priv)
>  	if (versatile_clcd_type == VEXPRESS_CLCD_V2M) {
>  		struct platform_device *pdev;
>  
> +		/* Registers a driver for the muxfpga */
> +		ret = vexpress_muxfpga_init();
> +		if (ret) {
> +			dev_err(dev, "unable to intialize muxfpga driver\n");
> +			return ret;
> +		}
> +
>  		/* Call into deep Vexpress configuration API */
>  		pdev = of_find_device_by_node(np);
>  		if (!pdev) {
> diff --git a/drivers/gpu/drm/pl111/pl111_vexpress.c b/drivers/gpu/drm/pl111/pl111_vexpress.c
> index c9fee625faf1..c30f63cd66a8 100644
> --- a/drivers/gpu/drm/pl111/pl111_vexpress.c
> +++ b/drivers/gpu/drm/pl111/pl111_vexpress.c
> @@ -106,7 +106,6 @@ static int vexpress_muxfpga_probe(struct platform_device *pdev)
>  	if (IS_ERR(map))
>  		return PTR_ERR(map);
>  	dev_set_drvdata(dev, map);
> -

nit: unrelated whitespace change

>  	return 0;
>  }
>  
> @@ -122,4 +121,13 @@ static struct platform_driver vexpress_muxfpga_driver = {
>  	.probe = vexpress_muxfpga_probe,
>  };
>  
> -builtin_platform_driver(vexpress_muxfpga_driver);
> +int vexpress_muxfpga_init(void)
> +{
> +	int ret;
> +
> +	ret = platform_driver_register(&vexpress_muxfpga_driver);
> +	/* -EBUSY just means this driver is already registered */
> +	if (ret && ret != -EBUSY)
> +		return ret;
> +	return 0;

fwiw, i think it'd be cleaner to do:

        /* -EBUSY just means this driver is already registered */
        if (ret == -EBUSY)
                ret = 0;
        return ret;

or if you're one of those people who doesn't mind inline conditionals:

        /* -EBUSY just means this driver is already registered */
        return ret == -EBUSY ? 0 : ret;


Anyways, just verbalizing my personal code style. With the whitespace fix,

Reviewed-by: Sean Paul <seanpaul@chromium.org>

> +}
> diff --git a/drivers/gpu/drm/pl111/pl111_vexpress.h b/drivers/gpu/drm/pl111/pl111_vexpress.h
> index 49876417f7b6..40fbe42369dc 100644
> --- a/drivers/gpu/drm/pl111/pl111_vexpress.h
> +++ b/drivers/gpu/drm/pl111/pl111_vexpress.h
> @@ -10,6 +10,8 @@ int pl111_vexpress_clcd_init(struct device *dev,
>  			     struct pl111_drm_dev_private *priv,
>  			     struct regmap *map);
>  
> +int vexpress_muxfpga_init(void);
> +
>  #else
>  
>  static int inline pl111_vexpress_clcd_init(struct device *dev,
> @@ -19,4 +21,9 @@ static int inline pl111_vexpress_clcd_init(struct device *dev,
>  	return -ENODEV;
>  }
>  
> +static inline int vexpress_muxfpga_init(void)
> +{
> +	return 0;
> +}
> +
>  #endif
> -- 
> 2.17.0
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS