linux-kernel - [PATCH] nvidia/noveau: Fix color mask

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Message-ID: <20151119211006.75c1d924@wiggum>
Date:	Thu, 19 Nov 2015 21:10:06 +0100
From:	Michael Büsch <m@...s.ch>
To:	dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
	Antonino Daplas <adaplas@...il.com>,
	linux-fbdev@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] nvidia/noveau: Fix color mask

The expression (~0 >> x) will always yield all-ones, because the right
shift is an arithmetic right shift that will always shift ones in.
Accordingly ~(~0 >> x) will always be zero.
Hence 'mask' will always be zero in this case.

Fix this by forcing a logical right shift instead of an arithmetic
right shift by using an unsigned int constant.

Signed-off-by: Michael Buesch <m@...s.ch>

---

This patch is untested, because I do not have the hardware.

Resend: Patch was originally sent on Wed, 17 Jun 2015.


Index: linux/drivers/gpu/drm/nouveau/nv50_fbcon.c
===================================================================
--- linux.orig/drivers/gpu/drm/nouveau/nv50_fbcon.c
+++ linux/drivers/gpu/drm/nouveau/nv50_fbcon.c
@@ -96,7 +96,7 @@ nv50_fbcon_imageblit(struct fb_info *inf
 	struct nouveau_drm *drm = nouveau_drm(nfbdev->dev);
 	struct nouveau_channel *chan = drm->channel;
 	uint32_t width, dwords, *data = (uint32_t *)image->data;
-	uint32_t mask = ~(~0 >> (32 - info->var.bits_per_pixel));
+	uint32_t mask = ~(~0U >> (32 - info->var.bits_per_pixel));
 	uint32_t *palette = info->pseudo_palette;
 	int ret;
 
Index: linux/drivers/gpu/drm/nouveau/nvc0_fbcon.c
===================================================================
--- linux.orig/drivers/gpu/drm/nouveau/nvc0_fbcon.c
+++ linux/drivers/gpu/drm/nouveau/nvc0_fbcon.c
@@ -96,7 +96,7 @@ nvc0_fbcon_imageblit(struct fb_info *inf
 	struct nouveau_drm *drm = nouveau_drm(nfbdev->dev);
 	struct nouveau_channel *chan = drm->channel;
 	uint32_t width, dwords, *data = (uint32_t *)image->data;
-	uint32_t mask = ~(~0 >> (32 - info->var.bits_per_pixel));
+	uint32_t mask = ~(~0U >> (32 - info->var.bits_per_pixel));
 	uint32_t *palette = info->pseudo_palette;
 	int ret;
 
Index: linux/drivers/video/fbdev/nvidia/nv_accel.c
===================================================================
--- linux.orig/drivers/video/fbdev/nvidia/nv_accel.c
+++ linux/drivers/video/fbdev/nvidia/nv_accel.c
@@ -351,7 +351,7 @@ static void nvidiafb_mono_color_expand(s
 				       const struct fb_image *image)
 {
 	struct nvidia_par *par = info->par;
-	u32 fg, bg, mask = ~(~0 >> (32 - info->var.bits_per_pixel));
+	u32 fg, bg, mask = ~(~0U >> (32 - info->var.bits_per_pixel));
 	u32 dsize, width, *data = (u32 *) image->data, tmp;
 	int j, k = 0;
 

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