Re: [PATCH v8 7/7] rust: drm/gem: Add vmap functions to shmem bindings

[Lyude Paul <lyude@redhat.com>]

On Wed, 2026-03-11 at 15:52 -0400, Lyude Paul wrote:
> 
> +
> +    /// Attempt to create a [`RawIoSysMap`] from the gem object.
> +    fn raw_vmap(&self) -> Result<*mut c_void> {
> +        let mut map: MaybeUninit<bindings::iosys_map> = MaybeUninit::uninit();
> +
> +        // SAFETY: drm_gem_shmem_vmap can be called with the DMA reservation lock held
> +        to_result(unsafe {
> +            // TODO: see top of file
> +            bindings::dma_resv_lock(self.raw_dma_resv(), ptr::null_mut());
> +            let ret = bindings::drm_gem_shmem_vmap_locked(self.as_raw_shmem(), map.as_mut_ptr());
> +            bindings::dma_resv_unlock(self.raw_dma_resv());
> +            ret
> +        })?;
> +
> +        // SAFETY: The call to drm_gem_shmem_vunmap_locked succeeded above, so we are guaranteed
> +        // that map is properly initialized.
> +        let map = unsafe { map.assume_init() };
> +
> +        // XXX: We don't currently support iomem allocations
> +        if map.is_iomem {
> +            // SAFETY:
> +            // - The vmap operation above succeeded, making it safe to call vunmap
> +            // - We checked that this is an iomem allocation, making it safe to read vaddr_iomem
> +            unsafe { self.raw_vunmap(map.__bindgen_anon_1.vaddr_iomem) };
> +
> +            Err(ENOTSUPP)
> +        } else {
> +            // SAFETY: We checked that this is not an iomem allocation, making it safe to read vaddr
> +            Ok(unsafe { map.__bindgen_anon_1.vaddr })
> +        }
> +    }
> +

I am missing a size check here to confirm that SIZE is valid, whoops. Will fix
in the next version (though, hopefully that will be the final one)

-- 
Cheers,
 Lyude Paul (she/her)
 Senior Software Engineer at Red Hat

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