[PATCH v2] staging: sm750fb: fix mono image source stride mismatch in lynxfb_ops_imageblit()
From: Muhammad Bilal <hidden>
Date: 2026-07-18 10:31:37
Also in:
linux-staging, lkml
Subsystem:
staging - silicon motion sm750 frame buffer driver, staging subsystem, the rest · Maintainers:
Sudip Mukherjee, Teddy Wang, Greg Kroah-Hartman, Linus Torvalds
sm750_hw_imageblit() advances its monochrome source pointer by
src_delta per scanline, and computes the correct rounded-up stride
internally as:
bytes_per_scan = (width + start_bit + 7) / 8;
Its only caller, lynxfb_ops_imageblit(), instead passed src_delta as
image->width >> 3. For widths not a multiple of 8 this under-counted
the stride, so the source pointer fell further behind the real
per-scanline layout on every line, corrupting the rendered image.
Rather than just fixing the caller's calculation, remove src_delta
as a parameter entirely and have sm750_hw_imageblit() advance by the
bytes_per_scan it already computes for itself. There has only ever
been one caller, and that caller was passing an out-of-sync
derivative of the same width/start_bit values sm750_hw_imageblit()
already has, so keeping stride as a separate parameter served no
purpose beyond letting the two calculations drift apart, which is
exactly what happened here.
Fixes: 81dee67e215b2 ("staging: sm750fb: add sm750 to staging")
Signed-off-by: Muhammad Bilal <redacted>
---
drivers/staging/sm750fb/sm750.c | 2 +-
drivers/staging/sm750fb/sm750.h | 2 +-
drivers/staging/sm750fb/sm750_accel.c | 6 ++----
drivers/staging/sm750fb/sm750_accel.h | 4 +---
4 files changed, 5 insertions(+), 9 deletions(-)
diff --git a/drivers/staging/sm750fb/sm750.c b/drivers/staging/sm750fb/sm750.c
index 89c811e0806c..da0b4979a281 100644
--- a/drivers/staging/sm750fb/sm750.c
+++ b/drivers/staging/sm750fb/sm750.c@@ -261,7 +261,7 @@ static void lynxfb_ops_imageblit(struct fb_info *info, spin_lock(&sm750_dev->slock); sm750_dev->accel.de_imageblit(&sm750_dev->accel, - image->data, image->width >> 3, 0, + image->data, 0, base, pitch, bpp, image->dx, image->dy, image->width, image->height,
diff --git a/drivers/staging/sm750fb/sm750.h b/drivers/staging/sm750fb/sm750.h
index d2c522e67f26..83229fe155ec 100644
--- a/drivers/staging/sm750fb/sm750.h
+++ b/drivers/staging/sm750fb/sm750.h@@ -73,7 +73,7 @@ struct lynx_accel { u32 rop2); int (*de_imageblit)(struct lynx_accel *accel, const char *p_srcbuf, - u32 src_delta, u32 start_bit, u32 d_base, u32 d_pitch, + u32 start_bit, u32 d_base, u32 d_pitch, u32 byte_per_pixel, u32 dx, u32 dy, u32 width, u32 height, u32 f_color, u32 b_color, u32 rop2);
diff --git a/drivers/staging/sm750fb/sm750_accel.c b/drivers/staging/sm750fb/sm750_accel.c
index 0316ea69d009..bac9a209899c 100644
--- a/drivers/staging/sm750fb/sm750_accel.c
+++ b/drivers/staging/sm750fb/sm750_accel.c@@ -288,8 +288,6 @@ static unsigned int de_get_transparency(struct lynx_accel *accel) * sm750_hw_imageblit * @accel: Acceleration device data * @src_buf: pointer to start of source buffer in system memory - * @src_delta: Pitch value (in bytes) of the source buffer, +ive means top down - * and -ive mean button up * @start_bit: Mono data can start at any bit in a byte, this value should be * 0 to 7 * @dest_base: Address of destination: offset in frame buffer
@@ -304,7 +302,7 @@ static unsigned int de_get_transparency(struct lynx_accel *accel) * @rop2: ROP value */ int sm750_hw_imageblit(struct lynx_accel *accel, const char *src_buf, - u32 src_delta, u32 start_bit, u32 dest_base, u32 dest_pitch, + u32 start_bit, u32 dest_base, u32 dest_pitch, u32 byte_per_pixel, u32 dx, u32 dy, u32 width, u32 height, u32 fg_color, u32 bg_color, u32 rop2) {
@@ -395,7 +393,7 @@ int sm750_hw_imageblit(struct lynx_accel *accel, const char *src_buf, write_dp_port(accel, *(unsigned int *)remain); } - src_buf += src_delta; + src_buf += bytes_per_scan; } return 0;
diff --git a/drivers/staging/sm750fb/sm750_accel.h b/drivers/staging/sm750fb/sm750_accel.h
index d15a40cacb84..4f609d6af0fa 100644
--- a/drivers/staging/sm750fb/sm750_accel.h
+++ b/drivers/staging/sm750fb/sm750_accel.h@@ -220,8 +220,6 @@ int sm750_hw_copyarea(struct lynx_accel *accel, /** * sm750_hw_imageblit * @pSrcbuf: pointer to start of source buffer in system memory - * @srcDelta: Pitch value (in bytes) of the source buffer, +ive means top down - *>----- and -ive mean button up * @startBit: Mono data can start at any bit in a byte, this value should be *>----- 0 to 7 * @dBase: Address of destination: offset in frame buffer
@@ -236,7 +234,7 @@ int sm750_hw_copyarea(struct lynx_accel *accel, * @rop2: ROP value */ int sm750_hw_imageblit(struct lynx_accel *accel, const char *pSrcbuf, - u32 srcDelta, u32 startBit, u32 dBase, u32 dPitch, + u32 startBit, u32 dBase, u32 dPitch, u32 bytePerPixel, u32 dx, u32 dy, u32 width, u32 height, u32 fColor, u32 bColor, u32 rop2);
--
2.55.0