linux-kernel - Re: [PATCH 2/7] drm/gem-shmem: Export VM ops functions

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Message-ID: <19955673-4296-46a6-8b0b-2baab3cf68d0@amd.com>
Date: Wed, 19 Mar 2025 08:55:14 +0100
From: Christian König <christian.koenig@....com>
To: Daniel Almeida <daniel.almeida@...labora.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <benno.lossin@...ton.me>,
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>, Sumit Semwal <sumit.semwal@...aro.org>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org, linux-media@...r.kernel.org,
 linaro-mm-sig@...ts.linaro.org, Danilo Krummrich <dakr@...nel.org>,
 Asahi Lina <lina@...hilina.net>
Subject: Re: [PATCH 2/7] drm/gem-shmem: Export VM ops functions

Am 18.03.25 um 20:22 schrieb Daniel Almeida:
> From: Asahi Lina <lina@...hilina.net>
>
> There doesn't seem to be a way for the Rust bindings to get a
> compile-time constant reference to drm_gem_shmem_vm_ops, so we need to
> duplicate that structure in Rust... this isn't nice...

Well "isn't nice" is an understatement. We can have that as a short term hack, but I don't think that this is a doable long term solution.

For this particular case here it most likely doesn't matter, but operation pointer structures are often used to identify a certain class of object.

So exporting the functions and then re-creating the constant operation pointer structure in Rust doesn't work in some cases.

Regards,
Christian.

>
> Signed-off-by: Asahi Lina <lina@...hilina.net>
> Signed-off-by: Daniel Almeida <daniel.almeida@...labora.com>
> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 9 ++++++---
>  include/drm/drm_gem_shmem_helper.h     | 3 +++
>  2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index ec89e9499f5f02a2a35713669bf649dd2abb9938..be310db5863871604f3502ad1f419937d4c20a84 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -535,7 +535,7 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
>  
> -static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
> +vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
>  {
>  	struct vm_area_struct *vma = vmf->vma;
>  	struct drm_gem_object *obj = vma->vm_private_data;
> @@ -564,8 +564,9 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
>  
>  	return ret;
>  }
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_fault);
>  
> -static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
> +void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
>  {
>  	struct drm_gem_object *obj = vma->vm_private_data;
>  	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> @@ -586,8 +587,9 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
>  
>  	drm_gem_vm_open(vma);
>  }
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_open);
>  
> -static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
> +void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
>  {
>  	struct drm_gem_object *obj = vma->vm_private_data;
>  	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> @@ -598,6 +600,7 @@ static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
>  
>  	drm_gem_vm_close(vma);
>  }
> +EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_close);
>  
>  const struct vm_operations_struct drm_gem_shmem_vm_ops = {
>  	.fault = drm_gem_shmem_fault,
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index d22e3fb53631ab655748d7f6c628ffdb402f6324..b70d3cc35bd194e7cd718bee220408b5dda568bf 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -132,6 +132,9 @@ void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
>  			      struct drm_printer *p, unsigned int indent);
>  
>  extern const struct vm_operations_struct drm_gem_shmem_vm_ops;
> +vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf);
> +void drm_gem_shmem_vm_open(struct vm_area_struct *vma);
> +void drm_gem_shmem_vm_close(struct vm_area_struct *vma);
>  
>  /*
>   * GEM object functions
>