[PATCH resend] ov7670: clean up ov7670_read semantics

[PATCH resend] ov7670: clean up ov7670_read semantics

[Andres Salomon]

[note: this should probably go in for 2.6.26, as it fixes a bug in
ov7670_s_fmt where we incorrectly think that we've failed because we
return !0]


Cortland Setlow pointed out a bug in ov7670.c where the result from
ov7670_read() was just being checked for !0, rather than <0.  This
made me realize that ov7670_read's semantics were rather confusing;
it both fills in 'value' with the result, and returns it.  This is
goes against general kernel convention; so rather than fixing callers,
let's fix the function.

This makes ov7670_read return <0 in the case of an error, and 0 upon
success. Thus, code like:

res = ov7670_read(...);
if (!res)
	goto error;

..will work properly.

Signed-off-by: Cortland Setlow <csetlow@tower-research.com>
Signed-off-by: Andres Salomon <dilinger@debian.org>
Acked-by: Jonathan Corbet <corbet@lwn.net>
---
 drivers/media/video/ov7670.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/media/video/ov7670.c b/drivers/media/video/ov7670.c
index 2bc6bdc..d7bfd30 100644
--- a/drivers/media/video/ov7670.c
+++ b/drivers/media/video/ov7670.c
@@ -406,8 +406,10 @@ static int ov7670_read(struct i2c_client *c,
unsigned char reg, int ret;
 
 	ret = i2c_smbus_read_byte_data(c, reg);
-	if (ret >= 0)
+	if (ret >= 0) {
 		*value = (unsigned char) ret;
+		ret = 0;
+	}
 	return ret;
 }
 
-- 
1.5.5.3

Re: [PATCH resend] ov7670: clean up ov7670_read semantics

[Andrew Morton]

On Fri, 11 Jul 2008 16:52:16 -0400 Andres Salomon <dilinger@queued.net> wrote:

> [note: this should probably go in for 2.6.26, as it fixes a bug in
> ov7670_s_fmt where we incorrectly think that we've failed because we
> return !0]
> 

In which case 2.6.25.x wants the fix as well?

> 
> Cortland Setlow pointed out a bug in ov7670.c where the result from
> ov7670_read() was just being checked for !0, rather than <0.  This
> made me realize that ov7670_read's semantics were rather confusing;
> it both fills in 'value' with the result, and returns it.  This is
> goes against general kernel convention; so rather than fixing callers,
> let's fix the function.
> 
> This makes ov7670_read return <0 in the case of an error, and 0 upon
> success. Thus, code like:
> 
> res = ov7670_read(...);
> if (!res)
> 	goto error;
> 
> ..will work properly.
> 
> Signed-off-by: Cortland Setlow <csetlow@tower-research.com>
> Signed-off-by: Andres Salomon <dilinger@debian.org>
> Acked-by: Jonathan Corbet <corbet@lwn.net>
> ---
>  drivers/media/video/ov7670.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/media/video/ov7670.c b/drivers/media/video/ov7670.c
> index 2bc6bdc..d7bfd30 100644
> --- a/drivers/media/video/ov7670.c
> +++ b/drivers/media/video/ov7670.c
> @@ -406,8 +406,10 @@ static int ov7670_read(struct i2c_client *c,
> unsigned char reg, int ret;

You have some wordwrapping happening there.

>  	ret = i2c_smbus_read_byte_data(c, reg);
> -	if (ret >= 0)
> +	if (ret >= 0) {
>  		*value = (unsigned char) ret;
> +		ret = 0;
> +	}
>  	return ret;
>  }
>  
> -- 
> 1.5.5.3

Re: [PATCH resend] ov7670: clean up ov7670_read semantics

[Andres Salomon]

On Fri, 11 Jul 2008 15:19:19 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Fri, 11 Jul 2008 16:52:16 -0400 Andres Salomon
> <dilinger@queued.net> wrote:
> 
> > [note: this should probably go in for 2.6.26, as it fixes a bug in
> > ov7670_s_fmt where we incorrectly think that we've failed because we
> > return !0]
> > 
> 
> In which case 2.6.25.x wants the fix as well?
> 

Yep!

[...]
> > diff --git a/drivers/media/video/ov7670.c
> > b/drivers/media/video/ov7670.c index 2bc6bdc..d7bfd30 100644
> > --- a/drivers/media/video/ov7670.c
> > +++ b/drivers/media/video/ov7670.c
> > @@ -406,8 +406,10 @@ static int ov7670_read(struct i2c_client *c,
> > unsigned char reg, int ret;
> 
> You have some wordwrapping happening there.
> 

Eek, thanks.  The original send wasn't line-wrapped, I'm not sure how
that happened.