[PATCH v2 0/2] staging: sm750fb: improve error handling in de_wait path

[PATCH v2 0/2] staging: sm750fb: improve error handling in de_wait path

[Hungyu Lin]

This series improves error handling in the sm750fb driver.

The de_wait() helpers previously returned -1 on timeout, and
callers discarded the error code by always returning -1. This
series replaces -1 with -ETIMEDOUT and propagates the error code
to improve error reporting.

Patch 1 replaces -1 with -ETIMEDOUT in de_wait() helpers.
Patch 2 propagates error codes from de_wait().

v2:
- Restore the removed comment in sm750_accel.c as requested

Hungyu Lin (2):
  staging: sm750fb: return -ETIMEDOUT on timeout in de_wait functions
  staging: sm750fb: propagate error codes from de_wait()

 drivers/staging/sm750fb/sm750_accel.c | 20 +++++++++++++-------
 drivers/staging/sm750fb/sm750_hw.c    |  4 ++--
 2 files changed, 15 insertions(+), 9 deletions(-)

-- 
2.34.1

[PATCH v2 1/2] staging: sm750fb: return -ETIMEDOUT on timeout in de_wait functions

[Hungyu Lin]

The hw_sm750le_de_wait() and hw_sm750_de_wait() functions return -1
when a timeout occurs. Replace these with -ETIMEDOUT to use a proper
errno value and better describe the error condition.

All callers check the return value as non-zero, so this change does
not alter existing behavior.

Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
---
 drivers/staging/sm750fb/sm750_hw.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/sm750fb/sm750_hw.c b/drivers/staging/sm750fb/sm750_hw.c
index a2798d428663..3809401baa3a 100644
--- a/drivers/staging/sm750fb/sm750_hw.c
+++ b/drivers/staging/sm750fb/sm750_hw.c
@@ -502,7 +502,7 @@ int hw_sm750le_de_wait(void)
 			return 0;
 	}
 	/* timeout error */
-	return -1;
+	return -ETIMEDOUT;
 }
 
 int hw_sm750_de_wait(void)
@@ -520,7 +520,7 @@ int hw_sm750_de_wait(void)
 			return 0;
 	}
 	/* timeout error */
-	return -1;
+	return -ETIMEDOUT;
 }
 
 int hw_sm750_pan_display(struct lynxfb_crtc *crtc,
-- 
2.34.1

[PATCH v2 2/2] staging: sm750fb: propagate error codes from de_wait()

[Hungyu Lin]

The sm750 acceleration functions currently return -1 when
de_wait() fails, discarding the original error code.

Since de_wait() now returns proper errno values, propagate
the error code instead of returning -1.

Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
---
 drivers/staging/sm750fb/sm750_accel.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/sm750fb/sm750_accel.c b/drivers/staging/sm750fb/sm750_accel.c
index 0f94d859e91c..688ec262a8ed 100644
--- a/drivers/staging/sm750fb/sm750_accel.c
+++ b/drivers/staging/sm750fb/sm750_accel.c
@@ -90,14 +90,16 @@ int sm750_hw_fillrect(struct lynx_accel *accel,
 		      u32 color, u32 rop)
 {
 	u32 de_ctrl;
+	int ret;
 
-	if (accel->de_wait() != 0) {
+	ret = accel->de_wait();
+	if (ret) {
 		/*
-		 * int time wait and always busy,seems hardware
+		 * int time wait and always busy, seems hardware
 		 * got something error
 		 */
 		pr_debug("De engine always busy\n");
-		return -1;
+		return ret;
 	}
 
 	write_dpr(accel, DE_WINDOW_DESTINATION_BASE, base); /* dpr40 */
@@ -154,6 +156,7 @@ int sm750_hw_copyarea(struct lynx_accel *accel,
 		      unsigned int rop2)
 {
 	unsigned int direction, de_ctrl;
+	int ret;
 
 	direction = LEFT_TO_RIGHT;
 	/* Direction of ROP2 operation: 1 = Left to Right, (-1) = Right to Left */
@@ -263,8 +266,9 @@ int sm750_hw_copyarea(struct lynx_accel *accel,
 		   DE_WINDOW_WIDTH_DST_MASK) |
 		  (source_pitch / Bpp & DE_WINDOW_WIDTH_SRC_MASK)); /* dpr3c */
 
-	if (accel->de_wait() != 0)
-		return -1;
+	ret = accel->de_wait();
+	if (ret)
+		return ret;
 
 	write_dpr(accel, DE_SOURCE,
 		  ((sx << DE_SOURCE_X_K1_SHIFT) & DE_SOURCE_X_K1_MASK) |
@@ -326,14 +330,16 @@ int sm750_hw_imageblit(struct lynx_accel *accel, const char *src_buf,
 	unsigned int de_ctrl = 0;
 	unsigned char remain[4];
 	int i, j;
+	int ret;
 
 	start_bit &= 7; /* Just make sure the start bit is within legal range */
 	bytes_per_scan = (width + start_bit + 7) / 8;
 	words_per_scan = bytes_per_scan & ~3;
 	bytes_remain = bytes_per_scan & 3;
 
-	if (accel->de_wait() != 0)
-		return -1;
+	ret = accel->de_wait();
+	if (ret)
+		return ret;
 
 	/*
 	 * 2D Source Base.
-- 
2.34.1

Re: [PATCH v2 1/2] staging: sm750fb: return -ETIMEDOUT on timeout in de_wait functions

[Greg Kroah-Hartman]

On Thu, Apr 09, 2026 at 03:58:20PM +0000, Hungyu Lin wrote:
> The hw_sm750le_de_wait() and hw_sm750_de_wait() functions return -1
> when a timeout occurs. Replace these with -ETIMEDOUT to use a proper
> errno value and better describe the error condition.
> 
> All callers check the return value as non-zero, so this change does
> not alter existing behavior.
> 
> Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
> ---
>  drivers/staging/sm750fb/sm750_hw.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/sm750fb/sm750_hw.c b/drivers/staging/sm750fb/sm750_hw.c
> index a2798d428663..3809401baa3a 100644
> --- a/drivers/staging/sm750fb/sm750_hw.c
> +++ b/drivers/staging/sm750fb/sm750_hw.c
> @@ -502,7 +502,7 @@ int hw_sm750le_de_wait(void)
>  			return 0;
>  	}
>  	/* timeout error */
> -	return -1;
> +	return -ETIMEDOUT;
>  }
>  
>  int hw_sm750_de_wait(void)
> @@ -520,7 +520,7 @@ int hw_sm750_de_wait(void)
>  			return 0;
>  	}
>  	/* timeout error */
> -	return -1;
> +	return -ETIMEDOUT;

The comment should be removed at the same time, now that the code itself
documents it properly, right?

thanks,

greg k-h

Re: [PATCH v2 2/2] staging: sm750fb: propagate error codes from de_wait()

[Greg Kroah-Hartman]

On Thu, Apr 09, 2026 at 03:58:21PM +0000, Hungyu Lin wrote:
> The sm750 acceleration functions currently return -1 when
> de_wait() fails, discarding the original error code.
> 
> Since de_wait() now returns proper errno values, propagate
> the error code instead of returning -1.

You can use the full 72 columns for a changelog text.

> 
> Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
> ---
>  drivers/staging/sm750fb/sm750_accel.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/sm750fb/sm750_accel.c b/drivers/staging/sm750fb/sm750_accel.c
> index 0f94d859e91c..688ec262a8ed 100644
> --- a/drivers/staging/sm750fb/sm750_accel.c
> +++ b/drivers/staging/sm750fb/sm750_accel.c
> @@ -90,14 +90,16 @@ int sm750_hw_fillrect(struct lynx_accel *accel,
>  		      u32 color, u32 rop)
>  {
>  	u32 de_ctrl;
> +	int ret;
>  
> -	if (accel->de_wait() != 0) {
> +	ret = accel->de_wait();
> +	if (ret) {
>  		/*
> -		 * int time wait and always busy,seems hardware
> +		 * int time wait and always busy, seems hardware

Nice fix, but not part of this change to make :(

thanks,

greg k-h