[PATCH 3/3] drm/msm: hijack firmware fb's memory

[Rob Clark]

On Tue, Jul 11, 2017 at 10:17 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> Quoting Rob Clark (2017-07-11 14:38:22)
>> +static unsigned long hijack_firmware_fb(struct drm_device *dev)
>> +{
>> +       struct msm_drm_private *priv = dev->dev_private;
>> +       unsigned long size;
>> +       int i;
>> +
>> +       /* if we have simplefb/efifb, find it's aperture and hijack
>> +        * that before we kick out the firmware fb's.
>> +        *
>> +        * TODO we probably should hold registration_lock
>> +        */
>> +       for (i = 0; i < FB_MAX; i++) {
>> +               struct fb_info *fb = get_fb_info(i);
>> +
>> +               if (IS_ERR_OR_NULL(fb))
>> +                       continue;
>> +
>> +               if (!fb->apertures->count)
>
> Does get_fb_info() not return a reference if its apertures->count==0?

yeah, you are right.. overlooked that when converting from iterating
registered_fb[] table directly without taking a reference..

>> +                       continue;
>> +
>> +               /* if we find efifb or simplefb, we are about to
>> +                * kick them out, so hijack their memory:
>> +                */
>> +               if ((strcmp(fb->fix.id, "EFI VGA") == 0) ||
>> +                               (strcmp(fb->fix.id, "simple") == 0)) {
>> +
>> +                       priv->vram.paddr = fb->apertures->ranges[0].base;
>> +                       size = fb->apertures->ranges[0].size;
>> +               }
>> +
>> +               put_fb_info(fb);
>> +
>> +               if (size)
>> +                       return size;
>
> size is never initialised to 0. Perhaps just return the reference to the
> matching fb? Hopefully sidestepping a few of the worries about it
> disappearing during the probe.

I guess that would be a useful approach if I wanted a single helper
that did both this and kicking out firmware fb's..

BR,
-R