[PATCH] drm/i915: Clamp cursor coordinates to int16_t range

[PATCH] drm/i915: Clamp cursor coordinates to int16_t range

[ville.syrjala]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

We store cursor_x/y as int16_t internally, but the user provided
coordinates are int32_t. Clamp the coordinates so that they don't
overflow the int16_t. Since the cursor is only 64x64 in size, the
clamping can't cause any visual changes.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index d4a480c..8f554f3 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7272,8 +7272,8 @@ static int intel_crtc_cursor_move(struct drm_crtc *crtc, int x, int y)
 {
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 
-	intel_crtc->cursor_x = x;
-	intel_crtc->cursor_y = y;
+	intel_crtc->cursor_x = clamp_t(int, x, SHRT_MIN, SHRT_MAX);
+	intel_crtc->cursor_y = clamp_t(int, y, SHRT_MIN, SHRT_MAX);
 
 	if (intel_crtc->active)
 		intel_crtc_update_cursor(crtc, intel_crtc->cursor_bo != NULL);
-- 
1.8.1.5

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Re: [PATCH] drm/i915: Clamp cursor coordinates to int16_t range

[Chris Wilson]

On Mon, Oct 21, 2013 at 07:01:58PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> We store cursor_x/y as int16_t internally, but the user provided
> coordinates are int32_t. Clamp the coordinates so that they don't
> overflow the int16_t. Since the cursor is only 64x64 in size, the
> clamping can't cause any visual changes.

EINVAL? That would appear to be a nuisance as we don't already tell the
user off for being silly with the cursor position.

Bump the internal range? Future proof against tomorrow's 64k
super-ultra-high definition monitors?

The valid range for cursor is currently (-64, 8192) and we don't compute
relative cursor position, so we will be fine for a few years yet with
int16_t.
 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

Re: [PATCH] drm/i915: Clamp cursor coordinates to int16_t range

[Daniel Vetter]

On Mon, Oct 21, 2013 at 6:01 PM,  <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> We store cursor_x/y as int16_t internally, but the user provided
> coordinates are int32_t. Clamp the coordinates so that they don't
> overflow the int16_t. Since the cursor is only 64x64 in size, the
> clamping can't cause any visual changes.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>


For shits&giggles: You've bothered with a subtest for this in your crc
cursor test? Should be a one-liner and would neatly test whether QA
catches it ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [PATCH] drm/i915: Clamp cursor coordinates to int16_t range

[Ville Syrjälä]

On Mon, Oct 21, 2013 at 06:15:06PM +0200, Daniel Vetter wrote:
> On Mon, Oct 21, 2013 at 6:01 PM,  <ville.syrjala@linux.intel.com> wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > We store cursor_x/y as int16_t internally, but the user provided
> > coordinates are int32_t. Clamp the coordinates so that they don't
> > overflow the int16_t. Since the cursor is only 64x64 in size, the
> > clamping can't cause any visual changes.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> 
> For shits&giggles: You've bothered with a subtest for this in your crc
> cursor test? Should be a one-liner and would neatly test whether QA
> catches it ...

Yeah it's there. Actually I added the test before I knew the bug
existed. The test is what found the bug for me.

It's not a specific subtest though, but part of all the bigger
cursor-offscreen subtests. The subtest split I'm using there isn't
very fine grained. Maybe I should change that actually. It would
help in pinpointing the failing cases more accurately.

-- 
Ville Syrjälä
Intel OTC

Re: [PATCH] drm/i915: Clamp cursor coordinates to int16_t range

[Daniel Vetter]

On Mon, Oct 21, 2013 at 05:13:43PM +0100, Chris Wilson wrote:
> On Mon, Oct 21, 2013 at 07:01:58PM +0300, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > We store cursor_x/y as int16_t internally, but the user provided
> > coordinates are int32_t. Clamp the coordinates so that they don't
> > overflow the int16_t. Since the cursor is only 64x64 in size, the
> > clamping can't cause any visual changes.
> 
> EINVAL? That would appear to be a nuisance as we don't already tell the
> user off for being silly with the cursor position.
> 
> Bump the internal range? Future proof against tomorrow's 64k
> super-ultra-high definition monitors?
> 
> The valid range for cursor is currently (-64, 8192) and we don't compute
> relative cursor position, so we will be fine for a few years yet with
> int16_t.
>  
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

Queued for -next, thanks for the patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch