Re: [PATCH v3 04/10] drm/fbdev-generic: Initialize fb-helper structure in generic setup

From: Sam Ravnborg <sam@ravnborg.org>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: airlied@gmail.com, daniel@ffwll.ch,
	maarten.lankhorst@linux.intel.com, mripard@kernel.org,
	javierm@redhat.com, linux-samsung-soc@vger.kernel.org,
	linux-arm-msm@vger.kernel.org, intel-gfx@lists.freedesktop.org,
	dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org,
	linux-tegra@vger.kernel.org, freedreno@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 04/10] drm/fbdev-generic: Initialize fb-helper structure in generic setup
Date: Wed, 25 Jan 2023 22:03:33 +0100	[thread overview]
Message-ID: <Y9GZJcRKbaK0cYGo@ravnborg.org> (raw)
In-Reply-To: <20230125200415.14123-5-tzimmermann@suse.de>

Hi Thomas,

On Wed, Jan 25, 2023 at 09:04:09PM +0100, Thomas Zimmermann wrote:
> Initialize the fb-helper structure immediately after its allocation
> in drm_fbdev_generic_setup(). That will make it easier to fill it with
> driver-specific values, such as the preferred BPP.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
> ---
>  drivers/gpu/drm/drm_fbdev_generic.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c
> index 135d58b8007b..63f66325a8a5 100644
> --- a/drivers/gpu/drm/drm_fbdev_generic.c
> +++ b/drivers/gpu/drm/drm_fbdev_generic.c
> @@ -385,8 +385,6 @@ static int drm_fbdev_client_hotplug(struct drm_client_dev *client)
>  	if (dev->fb_helper)
>  		return drm_fb_helper_hotplug_event(dev->fb_helper);
>  
> -	drm_fb_helper_prepare(dev, fb_helper, &drm_fb_helper_generic_funcs);
> -
>  	ret = drm_fb_helper_init(dev, fb_helper);
>  	if (ret)
>  		goto err;

From the documentation:
The drm_fb_helper_prepare()
helper must be called first to initialize the minimum required to make
hotplug detection work.
...
To finish up the fbdev helper initialization, the
drm_fb_helper_init() function is called.

So this change do not follow the documentation as drm_fb_helper_init()
is now called before drm_fb_helper_prepare()

I did not follow all the code - but my gut feeling is that the
documentation is right.

	Sam

> @@ -456,12 +454,12 @@ void drm_fbdev_generic_setup(struct drm_device *dev,
>  	fb_helper = kzalloc(sizeof(*fb_helper), GFP_KERNEL);
>  	if (!fb_helper)
>  		return;
> +	drm_fb_helper_prepare(dev, fb_helper, &drm_fb_helper_generic_funcs);
>  
>  	ret = drm_client_init(dev, &fb_helper->client, "fbdev", &drm_fbdev_client_funcs);
>  	if (ret) {
> -		kfree(fb_helper);
>  		drm_err(dev, "Failed to register client: %d\n", ret);
> -		return;
> +		goto err_drm_client_init;
>  	}
>  
>  	/*
> @@ -484,5 +482,12 @@ void drm_fbdev_generic_setup(struct drm_device *dev,
>  		drm_dbg_kms(dev, "client hotplug ret=%d\n", ret);
>  
>  	drm_client_register(&fb_helper->client);
> +
> +	return;
> +
> +err_drm_client_init:
> +	drm_fb_helper_unprepare(fb_helper);
> +	kfree(fb_helper);
> +	return;
>  }
>  EXPORT_SYMBOL(drm_fbdev_generic_setup);
> -- 
> 2.39.0

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