[PATCH 2/2] drm/udl: Implement page_flip ioctl

[Dave Airlie]

On 8 July 2014 17:15, David Herrmann <dh.herrmann at gmail.com> wrote:
> Hi
>
> On Thu, Jul 3, 2014 at 12:13 AM, Stéphane Marchesin
> <marcheu at chromium.org> wrote:
>> This is a very crude page_flip implementation for UDL. There are ways
>> to make it better (make it asynchronous, make it do actual vsynced
>> flips...) but that's for another patch.
>>
>> Signed-off-by: Stéphane Marchesin <marcheu at chromium.org>
>> ---
>>  drivers/gpu/drm/udl/udl_modeset.c | 21 +++++++++++++++++++++
>>  1 file changed, 21 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/udl/udl_modeset.c b/drivers/gpu/drm/udl/udl_modeset.c
>> index cddc4fc..7dc3bd8 100644
>> --- a/drivers/gpu/drm/udl/udl_modeset.c
>> +++ b/drivers/gpu/drm/udl/udl_modeset.c
>> @@ -363,6 +363,26 @@ static void udl_crtc_destroy(struct drm_crtc *crtc)
>>         kfree(crtc);
>>  }
>>
>> +static int udl_crtc_page_flip(struct drm_crtc *crtc,
>> +                             struct drm_framebuffer *fb,
>> +                             struct drm_pending_vblank_event *event,
>> +                             uint32_t page_flip_flags)
>> +{
>> +       struct udl_framebuffer *ufb = to_udl_fb(fb);
>> +       struct drm_device *dev = crtc->dev;
>> +       unsigned long flags;
>> +
>> +       udl_handle_damage(ufb, 0, 0, fb->width, fb->height);
>> +
>> +       spin_lock_irqsave(&dev->event_lock, flags);
>> +       if (event)
>> +               drm_send_vblank_event(dev, 0, event);
>> +       spin_unlock_irqrestore(&dev->event_lock, flags);
>> +       crtc->fb = fb;
>
> Doesn't this break user-space that expects page-flip events to not
> occur more often than the refresh-rate? For instance, weston
> re-renders on each page-flip event. With this patch, it will never
> sleep on udl as it immediately gets the page-flip event back?

I don't think you can update the USB device quicker than the refresh rate :-P

though that might change if we ever get USB3!
Dave.