[PATCH] video/console: Clip the right margin clear to the visible region

For some unknown reason, yres_virtual was 2x larger the the size specified
by i915 and so when blit_clear_margins() tried to clear the full virtual
right-hand margin it tried to write far beyond the end of the buffer.

This limits the clear to only the visible portion of the right-hand
margin, similar to how the bottom margin is treated.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id8138
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Signed-off-by: Chris Wilson <redacted>
---
 drivers/video/console/bitblit.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/video/console/bitblit.c b/drivers/video/console/bitblit.c
index 28b1a83..9f89e5a 100644
--- a/drivers/video/console/bitblit.c
+++ b/drivers/video/console/bitblit.c

@@ -219,9 +219,9 @@ static void bit_clear_margins(struct vc_data *vc, struct fb_info *info,
 
 	if (rw && !bottom_only) {
 		region.dx = info->var.xoffset + rs;
-		region.dy = 0;
+		region.dy = info->var.yoffset;
 		region.width = rw;
-		region.height = info->var.yres_virtual;
+		region.height = info->var.yres;
 		info->fbops->fb_fillrect(info, &region);
 	}
 

-- 
1.7.9.1

Hi Chris,

On 03/26/2012 08:17 PM, Chris Wilson wrote:

For some unknown reason, yres_virtual was 2x larger the the size specified
by i915 and so when blit_clear_margins() tried to clear the full virtual
right-hand margin it tried to write far beyond the end of the buffer.

This limits the clear to only the visible portion of the right-hand
margin, similar to how the bottom margin is treated.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id8138

as you also found the root of the problem and posted a patch to fix i915
(or rather all KMS-based framebuffers) by validating the virtual
resolution in check var, I don't see any reason to apply this one. I'm
not sure about it, but changing the behaviour of this function might
cause some undesired changes in user experience and as there is no
problem with this code as is, I'd prefer to not change it.


Best regards,

Florian Tobias Schandinat

On Fri, 30 Mar 2012 01:16:32 +0000, Florian Tobias Schandinat [off-list ref] wrote:

Hi Chris,

On 03/26/2012 08:17 PM, Chris Wilson wrote:

quoted

For some unknown reason, yres_virtual was 2x larger the the size specified
by i915 and so when blit_clear_margins() tried to clear the full virtual
right-hand margin it tried to write far beyond the end of the buffer.

This limits the clear to only the visible portion of the right-hand
margin, similar to how the bottom margin is treated.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id8138

as you also found the root of the problem and posted a patch to fix i915
(or rather all KMS-based framebuffers) by validating the virtual
resolution in check var, I don't see any reason to apply this one. I'm
not sure about it, but changing the behaviour of this function might
cause some undesired changes in user experience and as there is no
problem with this code as is, I'd prefer to not change it.

Ok, thanks for the review. Preventing userspace from programming an
unhandled value of yres_virtual is definitely the way forward.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre