[PATCH v5 7/7] drm/simpledrm: add fbdev fallback support

[Noralf Trønnes]

Den 03.09.2016 14:04, skrev Noralf Trønnes:
>
> Den 02.09.2016 10:22, skrev David Herrmann:
>> Create a simple fbdev device during SimpleDRM setup so legacy user-space
>> and fbcon can use it.
>>
>> Signed-off-by: David Herrmann <dh.herrmann at gmail.com>
>
> [...]
>
>> diff --git a/drivers/gpu/drm/simpledrm/simpledrm_fbdev.c 
>> b/drivers/gpu/drm/simpledrm/simpledrm_fbdev.c
>
> [...]
>
>> +void sdrm_fbdev_bind(struct sdrm_device *sdrm)
>> +{
>> +    struct drm_fb_helper *fbdev;
>> +    int r;
>> +
>> +    fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
>> +    if (!fbdev)
>> +        return;
>> +
>> +    drm_fb_helper_prepare(sdrm->ddev, fbdev, &sdrm_fbdev_funcs);
>> +
>> +    r = drm_fb_helper_init(sdrm->ddev, fbdev, 1, 1);
>> +    if (r < 0)
>> +        goto error;
>> +
>> +    r = drm_fb_helper_single_add_all_connectors(fbdev);
>> +    if (r < 0)
>> +        goto error;
>> +
>> +    r = drm_fb_helper_initial_config(fbdev,
>> +                sdrm->ddev->mode_config.preferred_depth);
>> +    if (r < 0)
>> +        goto error;
>> +
>> +    if (!fbdev->fbdev)
>> +        goto error;
>> +
>> +    sdrm->fbdev = fbdev;
>> +    return;
>> +
>> +error:
>> +    drm_fb_helper_fini(fbdev);
>> +    kfree(fbdev);
>> +}
>> +
>> +void sdrm_fbdev_unbind(struct sdrm_device *sdrm)
>> +{
>> +    struct drm_fb_helper *fbdev = sdrm->fbdev;
>> +
>> +    if (!fbdev)
>> +        return;
>> +
>> +    sdrm->fbdev = NULL;
>> +    drm_fb_helper_unregister_fbi(fbdev);
>> +    cancel_work_sync(&fbdev->dirty_work);
>> +    drm_fb_helper_release_fbi(fbdev);
>> +    drm_framebuffer_unreference(fbdev->fb);
>
> I get a warning that there are still fb's left during unbind:
>
> [   48.666003] WARNING: CPU: 0 PID: 716 at 
> drivers/gpu/drm/drm_crtc.c:3855 drm_mode_config_cleanup+0x180/0x1f4 [drm]
>
> This worked:
>
> -       drm_framebuffer_unreference(fbdev->fb);
> +       drm_framebuffer_unregister_private(fbdev->fb);
> +       drm_framebuffer_cleanup(fbdev->fb);
>

Well not quite, this doesn't free the bo, so maybe this:

-       drm_framebuffer_unreference(fbdev->fb);
+       drm_framebuffer_unregister_private(fbdev->fb);
+       sdrm_fb_destroy(fbdev->fb);

IIRC the reason ref count doesn't drop to zero, had something to do with 
multiple
fb_set_par calls taking reference but not being dropped later.

Noralf.

>
> Noralf.
>
>> +    fbdev->fb = NULL;
>> +    drm_fb_helper_fini(fbdev);
>> +    kfree(fbdev);
>> +}
>
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