[Intel-gfx] [RESEND PATCH 1/3] drm/i915/dmabuf: Implement pwrite() callback

[Daniel Vetter]

On Thu, Oct 31, 2019 at 09:29:56AM +0100, Janusz Krzysztofik wrote:
> We need dmabuf specific pwrite() callback utilizing dma-buf API,
> otherwise GEM_PWRITE IOCTL will no longer work with dma-buf backed
> (i.e., PRIME imported) objects on hardware with no mappable aperture.
> 
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>

Do we have userspace for this (aside from igts)? Specifically for the
gen12 + dma-buf import + pwrite/read/whatever case you're fixing in this
series here.
-Daniel

> ---
>  drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 55 ++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> index 96ce95c8ac5a..93eea1031c82 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> @@ -248,9 +248,64 @@ static void i915_gem_object_put_pages_dmabuf(struct drm_i915_gem_object *obj,
>  				 DMA_BIDIRECTIONAL);
>  }
>  
> +static int i915_gem_object_pwrite_dmabuf(struct drm_i915_gem_object *obj,
> +					 const struct drm_i915_gem_pwrite *args)
> +{
> +	struct dma_buf *dmabuf = obj->base.import_attach->dmabuf;
> +	void __user *user_data = u64_to_user_ptr(args->data_ptr);
> +	struct file *file = dmabuf->file;
> +	const struct file_operations *fop = file->f_op;
> +	void __force *vaddr;
> +	int ret;
> +
> +	if (fop->write) {
> +		loff_t offset = args->offset;
> +
> +		/*
> +		 * fop->write() is supposed to call dma_buf_begin_cpu_access()
> +		 * if O_SYNC flag is set, avoid calling it twice
> +		 */
> +		if (!(file->f_flags & O_SYNC)) {
> +			ret = dma_buf_begin_cpu_access(dmabuf, DMA_TO_DEVICE);
> +			if (ret)
> +				return ret;
> +		}
> +
> +		ret = fop->write(file, user_data, args->size, &offset);
> +
> +		if (!(file->f_flags & O_SYNC))
> +			dma_buf_end_cpu_access(dmabuf, DMA_TO_DEVICE);
> +
> +		if (!ret)
> +			return 0;
> +	}
> +
> +	/* dma-buf file .write() not supported or failed, try dma_buf_vmap() */
> +	ret = dma_buf_begin_cpu_access(dmabuf, DMA_TO_DEVICE);
> +	if (ret)
> +		return ret;
> +
> +	vaddr = dma_buf_vmap(dmabuf);
> +	if (!vaddr)
> +		goto out_err;
> +
> +	ret = copy_from_user(vaddr + args->offset, user_data, args->size);
> +	dma_buf_vunmap(dmabuf, vaddr);
> +	if (!ret)
> +		goto out_end;
> +
> +out_err:
> +	/* fall back to GTT mapping */
> +	ret = -ENODEV;
> +out_end:
> +	dma_buf_end_cpu_access(dmabuf, DMA_TO_DEVICE);
> +	return ret;
> +}
> +
>  static const struct drm_i915_gem_object_ops i915_gem_object_dmabuf_ops = {
>  	.get_pages = i915_gem_object_get_pages_dmabuf,
>  	.put_pages = i915_gem_object_put_pages_dmabuf,
> +	.pwrite = i915_gem_object_pwrite_dmabuf,
>  };
>  
>  struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
> -- 
> 2.21.0
> 

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