The fb_blank() hook accepts 5 blanking levels which include 1 level designed
for console use only. Userspace is only aware of 4 levels. Thus, it's
possible for userspace to request VESA_VSYNC_SUSPEND which, in turn, is
interpreted by the fb driver as a request for FB_BLANK_NORMAL. A few drivers
return -EINVAL for this, confusing userspace apps that the driver may not
have VESA blanking support.
Fix by incrementing the blank value by one if the request originated from
userspace.
Signed-off-by: Antonino Daplas <[email protected]>
---
Ingo Oeser wrote:
> > May I suggest to hide this implementation detail?
> >
Yes. The change will be invisible to drivers.
Unfortunately, this may cause some userland breakage. X should work.
However, some apps may have been developed that uses the FB_BLANK constants
(DirectFB?). In these cases, they'll get a deeper blank level instead, so it
probably won't affect them significantly. A follow up patch that hides the
FB_BLANK constants may be worthwhile.
drivers/video/fbmem.c | 13 +++++++++++++
1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index d2dede6..5bed0fb 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -843,6 +843,19 @@ fb_blank(struct fb_info *info, int blank
{
int ret = -EINVAL;
+ /*
+ * The framebuffer core supports 5 blanking levels (FB_BLANK), whereas
+ * VESA defined only 4. The extra level, FB_BLANK_NORMAL, is a
+ * console invention and is not related to power management.
+ * Unfortunately, fb_blank callers, especially X, pass VESA constants
+ * leading to undefined behavior.
+ *
+ * To avoid confusion, fb_blank will assume VESA constants if coming
+ * from userspace, and FB_BLANK constants if coming from the kernel.
+ */
+ if (info->flags & FBINFO_MISC_USEREVENT && blank)
+ blank++;
+
if (blank > FB_BLANK_POWERDOWN)
blank = FB_BLANK_POWERDOWN;
-
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