[PATCH v3 1/3] drm: add prime helpers

[Laurent Pinchart]

Hi Aaron,

A bit late, but here's a small question.

On Tuesday 15 January 2013 12:47:42 Aaron Plattner wrote:
> Instead of reimplementing all of the dma_buf functionality in every driver,
> create helpers drm_prime_import and drm_prime_export that implement them in
> terms of new, lower-level hook functions:
> 
>   gem_prime_pin: callback when a buffer is created, used to pin buffers into
> GTT gem_prime_get_sg_table: convert a drm_gem_object to an sg_table for
> export gem_prime_import_sg_table: convert an sg_table into a drm_gem_object
> gem_prime_vmap, gem_prime_vunmap: map and unmap an object
> 
> These hooks are optional; drivers can opt in by using drm_gem_prime_import
> and drm_gem_prime_export as the .gem_prime_import and .gem_prime_export
> fields of struct drm_driver.
> 
> v2:
> - Drop .begin_cpu_access.  None of the drivers this code replaces
> implemented it.  Having it here was a leftover from when I was trying to
> include i915 in this rework.
> - Use mutex_lock instead of mutex_lock_interruptible, as these three drivers
> did.  This patch series shouldn't change that behavior.
> - Rename helpers to gem_prime_get_sg_table and gem_prime_import_sg_table.
>   Rename struct sg_table* variables to 'sgt' for clarity.
> - Update drm.tmpl for these new hooks.
> 
> v3:
> - Pass the vaddr down to the driver.  This lets drivers that just call
> vunmap on the pointer avoid having to store the pointer in their GEM
> private structures. - Move documentation into a /** DOC */ comment in
> drm_prime.c and include it in drm.tmpl with a !P line.  I tried to use !F
> lines to include documentation of the individual functions from drmP.h, but
> the docproc / kernel-doc scripts barf on that file, so hopefully this is
> good enough for now.
> - apply refcount fix from commit be8a42ae60addd8b6092535c11b42d099d6470ec
>   ("drm/prime: drop reference on imported dma-buf come from gem")
> 
> Signed-off-by: Aaron Plattner <aplattner at nvidia.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: David Airlie <airlied at linux.ie>
> ---
>  Documentation/DocBook/drm.tmpl |   4 +
>  drivers/gpu/drm/drm_prime.c    | 186 +++++++++++++++++++++++++++++++++++++-
>  include/drm/drmP.h             |  12 +++
>  3 files changed, 201 insertions(+), 1 deletion(-)

[snip]

> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 7f12573..366910d 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c

[snip]

> +/**
> + * DOC: PRIME Helpers
> + *
> + * Drivers can implement @gem_prime_export and @gem_prime_import in terms
> of + * simpler APIs by using the helper functions @drm_gem_prime_export and
> + * @drm_gem_prime_import.  These functions implement dma-buf support in
> terms of + * five lower-level driver callbacks:
> + *
> + * Export callbacks:
> + *
> + *  - @gem_prime_pin (optional): prepare a GEM object for exporting
> + *
> + *  - @gem_prime_get_sg_table: provide a scatter/gather table of pinned
> pages + *
> + *  - @gem_prime_vmap: vmap a buffer exported by your driver
> + *
> + *  - @gem_prime_vunmap: vunmap a buffer exported by your driver
> + *
> + * Import callback:
> + *
> + *  - @gem_prime_import_sg_table (import): produce a GEM object from
> another + *    driver's scatter/gather table
> + */
> +
> +struct dma_buf *drm_gem_prime_export(struct drm_device *dev,
> +				     struct drm_gem_object *obj, int flags)
> +{
> +	if (dev->driver->gem_prime_pin) {
> +		int ret = dev->driver->gem_prime_pin(obj);
> +		if (ret)
> +			return ERR_PTR(ret);
> +	}
> +	return dma_buf_export(obj, &drm_gem_prime_dmabuf_ops, obj->size,
> +			      0600);

Why do you use 0600 instead of the flags passed by the caller ?

> +}
> +EXPORT_SYMBOL(drm_gem_prime_export);

-- 
Regards,

Laurent Pinchart