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Subject[PATCH v2 4/6] drm: fix drm_mode_addfb() on big endian machines.
Date
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. Add
the quirk_addfb_prefer_host_byte_order field to mode_config, so drivers
can opt-in.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
include/drm/drm_mode_config.h | 14 ++++++++++++++
drivers/gpu/drm/drm_framebuffer.c | 11 +++++++++++
2 files changed, 25 insertions(+)

diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index 5d29f4ba6f..65020086c9 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -811,6 +811,20 @@ struct drm_mode_config {
uint32_t preferred_depth, prefer_shadow;
bool quirk_addfb_prefer_xbgr_30bpp;

+ /*
+ * @quirk_addfb_prefer_host_byte_order:
+ *
+ * When set to true drm_mode_addfb() will pick host byte order
+ * pixel_format when calling drm_mode_addfb2(). This is how
+ * drm_mode_addfb() should have worked from day one. It
+ * didn't though, so we ended up with quirks in both kernel
+ * and userspace drivers to deal with the broken behavior.
+ * Simply fixing drm_mode_addfb() unconditionally would break
+ * these drivers, so add a quirk bit here to allow drivers
+ * opt-in.
+ */
+ bool quirk_addfb_prefer_host_byte_order;
+
/**
* @async_page_flip: Does this device support async flips on the primary
* plane?
diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
index 888c4d53cf..f863f8a20f 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,
r.pixel_format == DRM_FORMAT_XRGB2101010)
r.pixel_format = DRM_FORMAT_XBGR2101010;

+ if (dev->mode_config.quirk_addfb_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
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