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

[PATCH 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 currently return -1 on timeout and callers
discard error codes 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 in callers instead of returning -1.

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 | 22 ++++++++++++----------
 drivers/staging/sm750fb/sm750_hw.c    |  4 ++--
 2 files changed, 14 insertions(+), 12 deletions(-)

-- 
2.34.1

[PATCH 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 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 | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/staging/sm750fb/sm750_accel.c b/drivers/staging/sm750fb/sm750_accel.c
index 0f94d859e91c..891d12a5e2cc 100644
--- a/drivers/staging/sm750fb/sm750_accel.c
+++ b/drivers/staging/sm750fb/sm750_accel.c
@@ -90,14 +90,12 @@ int sm750_hw_fillrect(struct lynx_accel *accel,
 		      u32 color, u32 rop)
 {
 	u32 de_ctrl;
+	int ret;
 
-	if (accel->de_wait() != 0) {
-		/*
-		 * int time wait and always busy,seems hardware
-		 * got something error
-		 */
+	ret = accel->de_wait();
+	if (ret) {
 		pr_debug("De engine always busy\n");
-		return -1;
+		return ret;
 	}
 
 	write_dpr(accel, DE_WINDOW_DESTINATION_BASE, base); /* dpr40 */
@@ -154,6 +152,7 @@ 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 +262,9 @@ 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 +326,16 @@ 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 2/2] staging: sm750fb: propagate error codes from de_wait()

[Greg Kroah-Hartman]

On Thu, Apr 09, 2026 at 02:41:19PM +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.
> 
> Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
> ---
>  drivers/staging/sm750fb/sm750_accel.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/staging/sm750fb/sm750_accel.c b/drivers/staging/sm750fb/sm750_accel.c
> index 0f94d859e91c..891d12a5e2cc 100644
> --- a/drivers/staging/sm750fb/sm750_accel.c
> +++ b/drivers/staging/sm750fb/sm750_accel.c
> @@ -90,14 +90,12 @@ int sm750_hw_fillrect(struct lynx_accel *accel,
>  		      u32 color, u32 rop)
>  {
>  	u32 de_ctrl;
> +	int ret;
>  
> -	if (accel->de_wait() != 0) {
> -		/*
> -		 * int time wait and always busy,seems hardware
> -		 * got something error
> -		 */

Why did you delete the comment?

And when did de_wait() start returning correct values?

thanks,

greg k-h

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

[Denny Lin]

Hi Greg,

> Why did you delete the comment?

The comment was removed as part of simplifying the code while
changing the error handling to propagate the return value from
de_wait(). I can restore or update it if needed.

> And when did de_wait() start returning correct values?

de_wait() starts returning a proper errno value in patch 1 of this
series, where the timeout return value is changed from -1 to
-ETIMEDOUT. This patch then propagates that error value.

Thanks,
Hungyu

On Thu, Apr 9, 2026 at 8:05 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Thu, Apr 09, 2026 at 02:41:19PM +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.
> >
> > Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
> > ---
> >  drivers/staging/sm750fb/sm750_accel.c | 22 ++++++++++++----------
> >  1 file changed, 12 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/staging/sm750fb/sm750_accel.c b/drivers/staging/sm750fb/sm750_accel.c
> > index 0f94d859e91c..891d12a5e2cc 100644
> > --- a/drivers/staging/sm750fb/sm750_accel.c
> > +++ b/drivers/staging/sm750fb/sm750_accel.c
> > @@ -90,14 +90,12 @@ int sm750_hw_fillrect(struct lynx_accel *accel,
> >                     u32 color, u32 rop)
> >  {
> >       u32 de_ctrl;
> > +     int ret;
> >
> > -     if (accel->de_wait() != 0) {
> > -             /*
> > -              * int time wait and always busy,seems hardware
> > -              * got something error
> > -              */
>
> Why did you delete the comment?
>
> And when did de_wait() start returning correct values?
>
> thanks,
>
> greg k-h

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

[Greg Kroah-Hartman]

On Thu, Apr 09, 2026 at 08:15:36AM -0700, Denny Lin wrote:
> Hi Greg,
> 

Odd email style, try replying inline in the real email, not at the top
please :)

> > Why did you delete the comment?
> 
> The comment was removed as part of simplifying the code while
> changing the error handling to propagate the return value from
> de_wait(). I can restore or update it if needed.

Please keep it.

> > And when did de_wait() start returning correct values?
> 
> de_wait() starts returning a proper errno value in patch 1 of this
> series, where the timeout return value is changed from -1 to
> -ETIMEDOUT. This patch then propagates that error value.

Ah, that wasn't obvious, sorry.

thanks,

greg k-h