linux-kernel - [PATCH] drm: add DRM_PRIME_CAP

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Date:   Wed, 10 Apr 2019 09:47:12 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Gerd Hoffmann <kraxel@...hat.com>,
        Dave Airlie <airlied@...hat.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] drm: add DRM_PRIME_CAP_LOCAL

Some drivers (for example qxl) support neither import nor export of
dma-bufs.  But you can still use dma-bufs to pass buffer references
from one process to another; drm_gem_prime_import() will figure the
dma-buf came from the same driver and just takes a reference in that
case instead of doing a full export/import.

Right now there is no way for userspace to figure it can do this.  Add
the new prime capability DRM_PRIME_CAP_LOCAL to indicate that.  Set the
bit for every driver which has the DRIVER_PRIME feature bit set.

Cc: Dave Airlie <airlied@...hat.com>
Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 include/uapi/drm/drm.h      | 1 +
 drivers/gpu/drm/drm_ioctl.c | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 236b01a1fabf..b6157d48dc1a 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -632,6 +632,7 @@ struct drm_gem_open {
 #define DRM_CAP_PRIME			0x5
 #define  DRM_PRIME_CAP_IMPORT		0x1
 #define  DRM_PRIME_CAP_EXPORT		0x2
+#define  DRM_PRIME_CAP_LOCAL		0x4
 #define DRM_CAP_TIMESTAMP_MONOTONIC	0x6
 #define DRM_CAP_ASYNC_PAGE_FLIP		0x7
 /*
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index d337f161909c..00599758783b 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -241,6 +241,8 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_
 	case DRM_CAP_PRIME:
 		req->value |= dev->driver->prime_fd_to_handle ? DRM_PRIME_CAP_IMPORT : 0;
 		req->value |= dev->driver->prime_handle_to_fd ? DRM_PRIME_CAP_EXPORT : 0;
+		req->value |= (dev->driver->driver_features & DRIVER_PRIME)
+			? DRM_PRIME_CAP_LOCAL : 0;
 		return 0;
 	case DRM_CAP_SYNCOBJ:
 		req->value = drm_core_check_feature(dev, DRIVER_SYNCOBJ);
-- 
2.18.1