Re: [PATCH 04/24] drm/vgem: Use devm_drm_dev_alloc

[Daniel Vetter <daniel.vetter@ffwll.ch>]

On Wed, Sep 9, 2020 at 1:01 PM Melissa Wen <melissa.srw@gmail.com> wrote:
>
> Hi Daniel,
>
> looks good to me, just a few things inline.
>
> On 09/04, Daniel Vetter wrote:
> > This means we also need to slightly restructure the exit code, so that
> > final cleanup of the drm_device is triggered by unregistering the
> > platform device. Note that devres is both clean up when the driver is
> > unbound (not the case for vgem, we don't bind), and also when unregistering
> > the device (very much the case for vgem). Therefore we can rely on devres
> > even though vgem isn't a proper platform device driver.
> >
> > This also somewhat untangles the load code, since the drm and platform device
> > setup are no longer interleaved, but two distinct steps.
> >
> > v2: use devres_open/release_group so we can use devm without real
> > hacks in the driver core or having to create an entire fake bus for
> > testing drivers. Might want to extract this into helpers eventually,
> > maybe as a mock_drm_dev_alloc or test_drm_dev_alloc.
> >
> > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Cc: Emil Velikov <emil.velikov@collabora.com>
> > Cc: Sean Paul <seanpaul@chromium.org>
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Sam Ravnborg <sam@ravnborg.org>
> > Cc: Rob Clark <robdclark@chromium.org>
> > ---
> >  drivers/gpu/drm/vgem/vgem_drv.c | 55 ++++++++++++++-------------------
> >  1 file changed, 24 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> > index 313339bbff90..f95537627463 100644
> > --- a/drivers/gpu/drm/vgem/vgem_drv.c
> > +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> > @@ -401,16 +401,8 @@ static int vgem_prime_mmap(struct drm_gem_object *obj,
> >       return 0;
> >  }
> >
> > -static void vgem_release(struct drm_device *dev)
> > -{
> > -     struct vgem_device *vgem = container_of(dev, typeof(*vgem), drm);
> > -
> > -     platform_device_unregister(vgem->platform);
> > -}
> > -
> >  static struct drm_driver vgem_driver = {
> >       .driver_features                = DRIVER_GEM | DRIVER_RENDER,
> > -     .release                        = vgem_release,
> >       .open                           = vgem_open,
> >       .postclose                      = vgem_postclose,
> >       .gem_free_object_unlocked       = vgem_gem_free_object,
> > @@ -442,48 +434,49 @@ static struct drm_driver vgem_driver = {
> >  static int __init vgem_init(void)
> >  {
> >       int ret;
> > +     struct platform_device *pdev;
> >
> > -     vgem_device = kzalloc(sizeof(*vgem_device), GFP_KERNEL);
> > -     if (!vgem_device)
> > -             return -ENOMEM;
> > +     pdev = platform_device_register_simple("vgem", -1, NULL, 0);
> > +     if (IS_ERR(pdev))
> > +             return PTR_ERR(vgem_device->platform);
> I caught this line right above.
> It should be: return PTR_ERR (pdev), right?

Yes I will fix.

> > -     vgem_device->platform =
> > -             platform_device_register_simple("vgem", -1, NULL, 0);
> > -     if (IS_ERR(vgem_device->platform)) {
> > -             ret = PTR_ERR(vgem_device->platform);
> > -             goto out_free;
> > +     if (!devres_open_group(&pdev->dev, NULL, GFP_KERNEL)) {
> > +             ret = -ENOMEM;
> > +             goto out_unregister;
> >       }
> >
> > -     dma_coerce_mask_and_coherent(&vgem_device->platform->dev,
> > +     dma_coerce_mask_and_coherent(&pdev->dev,
> >                                    DMA_BIT_MASK(64));
> > -     ret = drm_dev_init(&vgem_device->drm, &vgem_driver,
> > -                        &vgem_device->platform->dev);
> > -     if (ret)
> > -             goto out_unregister;
> > -     drmm_add_final_kfree(&vgem_device->drm, vgem_device);
> > +
> > +     vgem_device = devm_drm_dev_alloc(&pdev->dev, &vgem_driver,
> > +                                      struct vgem_device, drm);
> > +     if (IS_ERR(vgem_device)) {
> > +             ret = PTR_ERR(vgem_device);
> > +             goto out_devres;
> > +     }
> > +     vgem_device->platform = pdev;
> >
> >       /* Final step: expose the device/driver to userspace */
> >       ret = drm_dev_register(&vgem_device->drm, 0);
> >       if (ret)
> > -             goto out_put;
> > +             goto out_devres;
> >
> >       return 0;
> >
> > -out_put:
> > -     drm_dev_put(&vgem_device->drm);
> > -     platform_device_unregister(vgem_device->platform);
> > -     return ret;
> > +out_devres:
> > +     devres_release_group(&pdev->dev, NULL);
> >  out_unregister:
> > -     platform_device_unregister(vgem_device->platform);
> > -out_free:
> > -     kfree(vgem_device);
> > +     platform_device_unregister(pdev);
> >       return ret;
> >  }
> >
> >  static void __exit vgem_exit(void)
> >  {
> > +     struct platform_device *pdev = vgem_device->platform;
> > +
> Well, there has never been a check for a null vgem_device here before,
> as in vkms. Should?

I think it should, but that's kinda a separate patch. Want to type it?
-Daniel

> >       drm_dev_unregister(&vgem_device->drm);
> > -     drm_dev_put(&vgem_device->drm);
> > +     devres_release_group(&pdev->dev, NULL);
> > +     platform_device_unregister(pdev);
> >  }
> >
> >  module_init(vgem_init);
> > --
> > 2.28.0
>
> Apart from these two points,
>
> Reviewed-by: Melissa Wen <melissa.srw@gmail.com>
>
> Thanks!
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel



-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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