linux-kernel - [PATCH 3/5] drm: fix drm_mode_addfb() on big endian machines.

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Message-Id: <20180903105756.24912-4-kraxel@redhat.com>
Date:   Mon,  3 Sep 2018 12:57:54 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Gerd Hoffmann <kraxel@...hat.com>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 3/5] drm: fix drm_mode_addfb() on big endian machines.

Userspace on big endian machhines typically expects the ADDFB ioctl
returns a big endian framebuffer.  drm_mode_addfb() will call
drm_mode_addfb2() unconditionally with little endian DRM_FORMAT_*
values though, which is wrong.  This patch fixes that.

Drivers (both kernel and xorg) have quirks in place to deal with the
broken drm_mode_addfb() behavior.  Because of this we can't just change
drm_mode_addfb() behavior for everybody without breaking things.  So add
a new driver feature flag DRIVER_PREFER_HOST_BYTE_ORDER, so drivers can
opt-in.

Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 include/drm/drm_drv.h             |  1 +
 drivers/gpu/drm/drm_framebuffer.c | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 46a8009784..9cf12596cd 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -57,6 +57,7 @@ struct drm_printer;
 #define DRIVER_KMS_LEGACY_CONTEXT	0x20000
 #define DRIVER_SYNCOBJ                  0x40000
 #define DRIVER_PREFER_XBGR_30BPP        0x80000
+#define DRIVER_PREFER_HOST_BYTE_ORDER   0x100000
 
 /**
  * struct drm_driver - DRM driver structure
diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
index 88758096d5..ccbda8a2e9 100644
--- a/drivers/gpu/drm/drm_framebuffer.c
+++ b/drivers/gpu/drm/drm_framebuffer.c
@@ -124,6 +124,17 @@ int drm_mode_addfb(struct drm_device *dev, struct drm_mode_fb_cmd *or,
 	    dev->driver->driver_features & DRIVER_PREFER_XBGR_30BPP)
 		r.pixel_format = DRM_FORMAT_XBGR2101010;
 
+	if (dev->driver->driver_features & DRIVER_PREFER_HOST_BYTE_ORDER) {
+		if (r.pixel_format == DRM_FORMAT_XRGB8888)
+			r.pixel_format = DRM_FORMAT_HOST_XRGB8888;
+		if (r.pixel_format == DRM_FORMAT_ARGB8888)
+			r.pixel_format = DRM_FORMAT_HOST_ARGB8888;
+		if (r.pixel_format == DRM_FORMAT_RGB565)
+			r.pixel_format = DRM_FORMAT_HOST_RGB565;
+		if (r.pixel_format == DRM_FORMAT_XRGB1555)
+			r.pixel_format = DRM_FORMAT_HOST_XRGB1555;
+	}
+
 	ret = drm_mode_addfb2(dev, &r, file_priv);
 	if (ret)
 		return ret;
-- 
2.9.3