Re: [PATCH v5 08/11] drm/tyr: add BO-related ioctls

[Deborah Brouwer <deborah.brouwer@collabora.com>]

On Tue, Oct 27, 2026 at 12:41:01AM +0800, Ke Sun wrote:
> From: Alvin Sun <alvin.sun@linux.dev>
> 
> Implement BO_CREATE and BO_MMAP_OFFSET so userspace can allocate GPU
> buffers and obtain a DRM mmap offset for the generic mmap path.
> BO_CREATE page-aligns the requested size; BO_MMAP_OFFSET rejects
> NO_MMAP objects, which must never be CPU-mapped.
> 
> Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
> ---
>  drivers/gpu/drm/tyr/driver.rs |  2 ++
>  drivers/gpu/drm/tyr/file.rs   | 73 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/tyr/gem.rs    | 18 +++++++++--
>  3 files changed, 90 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tyr/driver.rs b/drivers/gpu/drm/tyr/driver.rs
> index c0f17bc4ce2c9..f4f31b24180b4 100644
> --- a/drivers/gpu/drm/tyr/driver.rs
> +++ b/drivers/gpu/drm/tyr/driver.rs
> @@ -227,6 +227,8 @@ impl drm::Driver for TyrDrmDriver {
>          (PANTHOR_VM_DESTROY, drm_panthor_vm_destroy, ioctl::RENDER_ALLOW, TyrDrmFileData::vm_destroy),
>          (PANTHOR_VM_BIND, drm_panthor_vm_bind, ioctl::RENDER_ALLOW, TyrDrmFileData::vm_bind),
>          (PANTHOR_VM_GET_STATE, drm_panthor_vm_get_state, ioctl::RENDER_ALLOW, TyrDrmFileData::vm_get_state),
> +        (PANTHOR_BO_CREATE, drm_panthor_bo_create, ioctl::RENDER_ALLOW, TyrDrmFileData::bo_create),
> +        (PANTHOR_BO_MMAP_OFFSET, drm_panthor_bo_mmap_offset, ioctl::RENDER_ALLOW, TyrDrmFileData::bo_mmap_offset),
>      }
>  }
>  
> diff --git a/drivers/gpu/drm/tyr/file.rs b/drivers/gpu/drm/tyr/file.rs
> index 22a74b4abf3de..9ffb42f0d8851 100644
> --- a/drivers/gpu/drm/tyr/file.rs
> +++ b/drivers/gpu/drm/tyr/file.rs
> @@ -250,6 +250,79 @@ pub(crate) fn vm_get_state(
>              Ok(0)
>          })
>      }
> +
> +    pub(crate) fn bo_create(
> +        ddev: &TyrDrmDevice<Registered>,
> +        _reg_data: &TyrDrmRegistrationData<'_>,
> +        bocreate: &mut uapi::drm_panthor_bo_create,
> +        file: &TyrDrmFile,
> +    ) -> Result<u32> {
> +        if bocreate.size == 0
> +            || bocreate.pad != 0
> +            || bocreate.flags & !uapi::drm_panthor_bo_flags_DRM_PANTHOR_BO_NO_MMAP != 0
> +        {
> +            dev_dbg!(
> +                ddev.as_ref(),
> +                "Invalid BO_CREATE params: size={}, pad={}, flags={:#x}\n",
> +                bocreate.size,
> +                bocreate.pad,
> +                bocreate.flags
> +            );
> +            return Err(EINVAL);
> +        }

Panthor checks that both BO_WB_MMAP and BO_NO_MMAP are not
set at the same time, should we do the same here?

Also if only BO_WB_MMAP is set, shouldn't we return EOPNOTSUPP?


> +
> +        if bocreate.exclusive_vm_id != 0 {
> +            dev_dbg!(ddev.as_ref(), "BO_CREATE: exclusive_vm_id not supported\n");
> +            return Err(EINVAL);

Return EOPNOTSUPP because it's a valid request we just don't support it.

> +        }
> +
> +        let size = usize::try_from(bocreate.size).map_err(|_| {
> +            dev_dbg!(
> +                ddev.as_ref(),
> +                "BO_CREATE size {:#x} too large\n",
> +                bocreate.size
> +            );
> +            EINVAL
> +        })?;
> +        let bo = crate::gem::new_object(ddev, size, bocreate.flags)?;

Use file.inner_with() to access the platform device with the bound
lifetime and then pass it to the new_object so that you can
avoid accessing it later with an unsafe block. Something like:

 let bo = file.inner_with(|pfile| {
    crate::gem::new_object(
        ddev,
        pfile.reg.pdev.as_ref(),
        size,
        bocreate.flags,
    )
 })?;

> +        bocreate.handle = bo.create_handle(file)?;
> +        bocreate.size = bo.size() as u64;

use u64::from_safe_cast(bo.size())


> +
> +        Ok(0)
> +    }
> +
> +    pub(crate) fn bo_mmap_offset(
> +        ddev: &TyrDrmDevice<Registered>,
> +        _reg_data: &TyrDrmRegistrationData<'_>,
> +        bommap: &mut uapi::drm_panthor_bo_mmap_offset,
> +        file: &TyrDrmFile,
> +    ) -> Result<u32> {
> +        if bommap.pad != 0 {
> +            dev_dbg!(
> +                ddev.as_ref(),
> +                "BO mmap offset pad not zero: {}\n",
> +                bommap.pad
> +            );
> +            return Err(EINVAL);
> +        }
> +
> +        let bo = crate::gem::lookup_handle(file, bommap.handle).inspect_err(|_| {
> +            dev_dbg!(ddev.as_ref(), "Invalid BO mmap handle: {}\n", bommap.handle);
> +        })?;
> +        if bo.flags() & uapi::drm_panthor_bo_flags_DRM_PANTHOR_BO_NO_MMAP != 0 {
> +            dev_dbg!(ddev.as_ref(), "BO mmap offset on NO_MMAP object\n");
> +            return Err(EPERM);
> +        }
> +        bommap.offset = bo.create_mmap_offset().inspect_err(|_| {
> +            dev_err!(
> +                ddev.as_ref(),
> +                "Failed to create mmap offset for handle {}\n",
> +                bommap.handle
> +            );
> +        })?;
> +
> +        Ok(0)
> +    }
>  }
>  
>  fn vm_bind_exec_op(vm: &Vm<'_>, file: &TyrDrmFile, op: &VmBindOp) -> Result {
> diff --git a/drivers/gpu/drm/tyr/gem.rs b/drivers/gpu/drm/tyr/gem.rs
> index 60f6363995a5a..14f3e182b98e2 100644
> --- a/drivers/gpu/drm/tyr/gem.rs
> +++ b/drivers/gpu/drm/tyr/gem.rs
> @@ -38,6 +38,13 @@ pub(crate) struct BoData {
>      flags: u32,
>  }
>  
> +impl BoData {
> +    /// Returns the flags the BO was created with.
> +    pub(crate) fn flags(&self) -> u32 {
> +        self.flags
> +    }
> +}
> +
>  /// Provides a way to pass arguments when creating BoData
>  /// as required by the gem::DriverObject trait.
>  pub(crate) struct BoCreateArgs {
> @@ -57,7 +64,6 @@ fn new(_dev: &TyrDrmDevice, _size: usize, args: BoCreateArgs) -> impl PinInit<Se
>  pub(crate) type Bo = gem::shmem::Object<BoData>;
>  
>  /// Create a new GEM buffer object.
> -#[expect(dead_code)]
>  pub(crate) fn new_object(ddev: &TyrDrmDevice, size: usize, flags: u32) -> Result<ARef<Bo>> {
>      if size == 0 {
>          return Err(EINVAL);
> @@ -65,7 +71,7 @@ pub(crate) fn new_object(ddev: &TyrDrmDevice, size: usize, flags: u32) -> Result
>  
>      let aligned_size = size.checked_next_multiple_of(PAGE_SIZE).ok_or(EINVAL)?;
>  
> -    Bo::new(
> +    let bo = Bo::new(
>          ddev,
>          aligned_size,
>          shmem::ObjectConfig {
> @@ -73,7 +79,13 @@ pub(crate) fn new_object(ddev: &TyrDrmDevice, size: usize, flags: u32) -> Result
>              parent_resv_obj: None,
>          },
>          BoCreateArgs { flags },
> -    )
> +    )?;
> +
> +    // SAFETY: `ddev` is bound for the duration of this call.
> +    let dev = unsafe { ddev.as_ref().as_ref().as_bound() };

You can remove this unsafe block by accessing the bound device through
file.inner_with()

> +    bo.sg_table(dev)?;
> +
> +    Ok(bo)
>  }
>  
>  /// Look up a GEM object by handle for a DRM file.
> 
> -- 
> 2.43.0
>