Re: [PATCH] nvidia/noveau: Fix color mask
From: Ilia Mirkin <hidden>
Date: 2015-06-18 00:47:17
Also in:
dri-devel, nouveau
On Wed, Jun 17, 2015 at 1:05 PM, Michael Büsch [off-list ref] wrote:
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@bues.ch>
Confirmed that this does indeed happen with
#include <stdio.h>
int main(int argc, char *argv[]) {
unsigned mask = ~(~0 >> (32 - (argv[1][0] - '0')));
printf("%08x\n", mask);
}
I guess fbdev/nvidia/nv_accel.c was the source of all this, as the
code is identical, and it probably came first.
FWIW this is
Reviewed-by: Ilia Mirkin <redacted>
quoted hunk ↗ jump to hunk
--- This patch is untested, because I do not have the hardware. 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;_______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel