Hi Jingfeng,
Am Dienstag, dem 18.07.2023 um 02:34 +0800 schrieb suijingfeng:
> Hi, Lucas
>
>
> Thanks for you guidance!
>
>
> On 2023/7/17 17:51, Lucas Stach wrote:
> > Hi Jingfeng,
> >
> > Am Freitag, dem 23.06.2023 um 18:08 +0800 schrieb Sui Jingfeng:
> > > From: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> > >
> > > Because it is not used by the etnaviv_gem_new_impl() function,
> > > no functional change.
> > >
> > I think it would make sense to move into the opposite direction: in
> > both callsites of etnaviv_gem_new_impl we immediately call
> > drm_gem_object_init with the size.
>
> Really?
>
> But there are multiple call path to the etnaviv_gem_new_impl() function.
>
>
> Code path 1 (PRIME):
>
> > - etnaviv_gem_prime_import_sg_table()
>
> > -- etnaviv_gem_new_private()
>
> > --- etnaviv_gem_new_impl(dev, size, flags, ops, &obj)
>
> > --- drm_gem_private_object_init(dev, obj, size)
>
>
> Code path 2 (USERPTR):
>
> > - etnaviv_gem_new_userptr()
>
> > -- etnaviv_gem_new_private()
>
> > --- etnaviv_gem_new_impl(dev, size, flags, ops, &obj)
>
> > --- drm_gem_private_object_init(dev, obj, size)
>
>
> Code path 3 (construct a GEM buffer object for the user-space):
>
> > - etnaviv_ioctl_gem_new()
>
> > -- etnaviv_gem_new_handle()
>
> > --- etnaviv_gem_new_impl(dev, size, flags, &etnaviv_gem_shmem_ops, &obj);
>
> > --- drm_gem_object_init(dev, obj, size);
>
>
> If I understand this correctly:
>
>
> Code path 1 is for cross device (and cross driver) buffer-sharing,
>
> Code path 2 is going to share the buffer the userspace,
>
>
> *Only* the code path 3 is to construct a GEM buffer object for the
> user-space the userspace,
>
> that is say, *only* the code path 3 need to do the backing memory
> allocation work for the userspace.
>
> thus it need to call drm_gem_object_init() function, which really the
> shmem do the backing memory
>
> allocation.
>
>
> The code path 1 and the code path 2 do not need the kernel space
> allocate the backing memory.
>
> Because they are going to share the buffer already allocated by others.
>
> thus, code path 2 and code path 3 should call drm_gem_private_object_init(),
>
> *not* the drm_gem_object_init() function.
>
>
> When import buffer from the a specific KMS driver,
>
> then etnaviv_gem_prime_import_sg_table() will be called.
>
>
> I guess you means that drm_gem_private_object_init() (not the
> drm_gem_object_init() function)here ?
>
>
> > A better cleanup would be to make
> > use of the size parameter and move this object init call into
> > etnaviv_gem_new_impl.
>
> If I following you guidance, how do I differentiate the cases
>
> when to call drm_gem_private_object_init() not drm_gem_object_init() ?
>
> and when call drm_gem_object_init() not drm_gem_private_object_init()?
>
>
> I don't think you are right here.
>
Yes, clearly I was not taking into account the differences between
drm_gem_private_object_init and drm_gem_object_init properly. Please
disregard my comment, this patch is good as-is.
Regards,
Lucas
> >
> > Regards,
> > Lucas
> >
> > > Signed-off-by: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> > > ---
> > > drivers/gpu/drm/etnaviv/etnaviv_gem.c | 7 +++----
> > > 1 file changed, 3 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > > index b5f73502e3dd..be2f459c66b5 100644
> > > --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > > @@ -542,7 +542,7 @@ static const struct drm_gem_object_funcs etnaviv_gem_object_funcs = {
> > > .vm_ops = &vm_ops,
> > > };
> > >
> > > -static int etnaviv_gem_new_impl(struct drm_device *dev, u32 size, u32 flags,
> > > +static int etnaviv_gem_new_impl(struct drm_device *dev, u32 flags,
> > > const struct etnaviv_gem_ops *ops, struct drm_gem_object **obj)
> > > {
> > > struct etnaviv_gem_object *etnaviv_obj;
> > > @@ -591,8 +591,7 @@ int etnaviv_gem_new_handle(struct drm_device *dev, struct drm_file *file,
> > >
> > > size = PAGE_ALIGN(size);
> > >
> > > - ret = etnaviv_gem_new_impl(dev, size, flags,
> > > - &etnaviv_gem_shmem_ops, &obj);
> > > + ret = etnaviv_gem_new_impl(dev, flags, &etnaviv_gem_shmem_ops, &obj);
> > > if (ret)
> > > goto fail;
> > >
> > > @@ -627,7 +626,7 @@ int etnaviv_gem_new_private(struct drm_device *dev, size_t size, u32 flags,
> > > struct drm_gem_object *obj;
> > > int ret;
> > >
> > > - ret = etnaviv_gem_new_impl(dev, size, flags, ops, &obj);
> > > + ret = etnaviv_gem_new_impl(dev, flags, ops, &obj);
> > > if (ret)
> > > return ret;
> > >
>
