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Date:   Wed, 19 Jun 2019 12:54:01 +0200
From:   Daniel Vetter <daniel@ffwll.ch>
To:     Gerd Hoffmann <kraxel@redhat.com>
Cc:     dri-devel@lists.freedesktop.org,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 01/12] drm: add gem array helpers
Message-ID: <20190619105401.GM12905@phenom.ffwll.local>
Mail-Followup-To: Gerd Hoffmann <kraxel@redhat.com>,
        dri-devel@lists.freedesktop.org,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        open list <linux-kernel@vger.kernel.org>
References: <20190619090420.6667-1-kraxel@redhat.com>
 <20190619090420.6667-2-kraxel@redhat.com>
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On Wed, Jun 19, 2019 at 11:04:09AM +0200, Gerd Hoffmann wrote:
> Add struct and helper functions to manage an array of gem objects.
> See added kernel docs for details.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

Hm, feels like jumping ahead here, I think there's too much still
in-flight:
- Christian is pondering some improved ww_mutex lock/unlock helpers.
  That'll probably change a lot of this code too.
- If we do more helpers, then I think we should have a consistent story
  across everything. These here don't really fit into the existing gem
  lock/unlock helpers.
- We probably want to design something coherent to replace all the ttm
  execbuf utils, i.e. bo lookup, locking, updating reservation objects,
  all that.
- I think this needs more than one driver to proof itself.

Maybe long-term we could have a drm_gem_eu_helper.c or so which contains
all that. But that's still some ways off.

I'd go back to the virtio-only conversion, and once we have more of this
stuff settled, we can look at how to properly design some nice&consistent
helpers.

Cheers, Daniel
> ---
>  include/drm/drm_gem_array_helper.h     | 15 +++++
>  drivers/gpu/drm/drm_gem_array_helper.c | 76 ++++++++++++++++++++++++++
>  drivers/gpu/drm/Makefile               |  3 +-
>  3 files changed, 93 insertions(+), 1 deletion(-)
>  create mode 100644 include/drm/drm_gem_array_helper.h
>  create mode 100644 drivers/gpu/drm/drm_gem_array_helper.c
> 
> diff --git a/include/drm/drm_gem_array_helper.h b/include/drm/drm_gem_array_helper.h
> new file mode 100644
> index 000000000000..adf7961247b3
> --- /dev/null
> +++ b/include/drm/drm_gem_array_helper.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __DRM_GEM_ARRAY_HELPER_H__
> +#define __DRM_GEM_ARRAY_HELPER_H__
> +
> +struct drm_gem_object_array {
> +	u32 nents;
> +	struct drm_gem_object *objs[];
> +};
> +
> +struct drm_gem_object_array *drm_gem_array_alloc(u32 nents);
> +struct drm_gem_object_array *
> +drm_gem_array_from_handles(struct drm_file *drm_file, u32 *handles, u32 nents);
> +void drm_gem_array_put_free(struct drm_gem_object_array *objs);
> +
> +#endif /* __DRM_GEM_ARRAY_HELPER_H__ */
> diff --git a/drivers/gpu/drm/drm_gem_array_helper.c b/drivers/gpu/drm/drm_gem_array_helper.c
> new file mode 100644
> index 000000000000..d35c77c4a02d
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_gem_array_helper.c
> @@ -0,0 +1,76 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#include <drm/drm_gem.h>
> +#include <drm/drm_gem_array_helper.h>
> +
> +/**
> + * drm_gem_array_alloc -- allocate gem object array of the given size.
> + *
> + * @nents: number of entries needed.
> + *
> + * Returns: An array of gem objects on success, NULL on failure.
> + */
> +struct drm_gem_object_array *drm_gem_array_alloc(u32 nents)
> +{
> +	struct drm_gem_object_array *objs;
> +	size_t size = sizeof(*objs) + sizeof(objs->objs[0]) * nents;
> +
> +	objs = kzalloc(size, GFP_KERNEL);
> +	if (!objs)
> +		return NULL;
> +
> +	objs->nents = nents;
> +	return objs;
> +}
> +EXPORT_SYMBOL(drm_gem_array_alloc);
> +
> +static void drm_gem_array_free(struct drm_gem_object_array *objs)
> +{
> +	kfree(objs);
> +}
> +
> +/**
> + * drm_gem_array_from_handles -- lookup an array of gem handles.
> + *
> + * @drm_file: drm file-private structure to use for the handle look up
> + * @handles: the array of handles to lookup.
> + * @nents: the numer of handles.
> + *
> + * Returns: An array of gem objects on success, NULL on failure.
> + */
> +struct drm_gem_object_array*
> +drm_gem_array_from_handles(struct drm_file *drm_file, u32 *handles, u32 nents)
> +{
> +	struct drm_gem_object_array *objs;
> +	u32 i;
> +
> +	objs = drm_gem_array_alloc(nents);
> +	if (!objs)
> +		return NULL;
> +
> +	for (i = 0; i < nents; i++) {
> +		objs->objs[i] = drm_gem_object_lookup(drm_file, handles[i]);
> +		if (!objs->objs[i]) {
> +			drm_gem_array_put_free(objs);
> +			return NULL;
> +		}
> +	}
> +	return objs;
> +}
> +
> +/**
> + * drm_gem_array_put_free -- put gem objects and free array.
> + *
> + * @objs: the gem object array.
> + */
> +void drm_gem_array_put_free(struct drm_gem_object_array *objs)
> +{
> +	u32 i;
> +
> +	for (i = 0; i < objs->nents; i++) {
> +		if (!objs->objs[i])
> +			continue;
> +		drm_gem_object_put_unlocked(objs->objs[i]);
> +	}
> +	drm_gem_array_free(objs);
> +}
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 9d630a28a788..d32e7de0937b 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -43,7 +43,8 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_dsc.o drm_probe_helper
>  		drm_simple_kms_helper.o drm_modeset_helper.o \
>  		drm_scdc_helper.o drm_gem_framebuffer_helper.o \
>  		drm_atomic_state_helper.o drm_damage_helper.o \
> -		drm_format_helper.o drm_self_refresh_helper.o
> +		drm_format_helper.o drm_self_refresh_helper.o \
> +		drm_gem_array_helper.o
>  
>  drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
>  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
> -- 
> 2.18.1
> 

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