Re: [PATCH] staging: greybus: Clear up precedence for gcam logging macros

[Jackson Chui <jacksonchui.qwerty@gmail.com>]

On Sat, Apr 06, 2024 at 11:45:51AM -0500, Alex Elder wrote:
> On 4/6/24 4:09 AM, Dan Carpenter wrote:
> > On Fri, Apr 05, 2024 at 02:22:05PM -0700, Jackson Chui wrote:
> > > On Thu, Apr 04, 2024 at 05:05:09PM -0500, Alex Elder wrote:
> > > > On 4/3/24 7:16 PM, Jackson Chui wrote:
> > > > > Reported by checkpatch:
> > > > > 
> > > > > CHECK: Macro argument 'gcam' may be better as '(gcam)' to avoid
> > > > > precedence issues
> > > > 
> > > > I agree with your argument about the way the macro should be
> > > > defined.  But perhaps these gcam_*() functions could just
> > > > be eliminated?
> > > > 
> > > > I see 15 calls to gcam_err(), 1 call to gcam_dbg(), and none
> > > > to gcam_info().  It would be a different patch, but maybe
> > > > you could do that instead?
> > > > 
> > > > 					-Alex
> > > > 
> > > > 
> > > > > 
> > > > > Disambiguates '&' (address-of) operator and '->' operator precedence,
> > > > > accounting for how '(gcam)->bundle->dev' is a 'struct device' and not a
> > > > > 'struct device*', which is required by the dev_{dbg,info,err} driver
> > > > > model diagnostic macros. Issue found by checkpatch.
> > > > > 
> > > > > Signed-off-by: Jackson Chui <jacksonchui.qwerty@gmail.com>
> > > > > ---
> > > > >    drivers/staging/greybus/camera.c | 6 +++---
> > > > >    1 file changed, 3 insertions(+), 3 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/staging/greybus/camera.c b/drivers/staging/greybus/camera.c
> > > > > index a8173aa3a995..d82a2d2abdca 100644
> > > > > --- a/drivers/staging/greybus/camera.c
> > > > > +++ b/drivers/staging/greybus/camera.c
> > > > > @@ -180,9 +180,9 @@ static const struct gb_camera_fmt_info *gb_camera_get_format_info(u16 gb_fmt)
> > > > >    #define GB_CAMERA_MAX_SETTINGS_SIZE	8192
> > > > > -#define gcam_dbg(gcam, format...)	dev_dbg(&gcam->bundle->dev, format)
> > > > > -#define gcam_info(gcam, format...)	dev_info(&gcam->bundle->dev, format)
> > > > > -#define gcam_err(gcam, format...)	dev_err(&gcam->bundle->dev, format)
> > > > > +#define gcam_dbg(gcam, format...)	dev_dbg(&((gcam)->bundle->dev), format)
> > > > > +#define gcam_info(gcam, format...)	dev_info(&((gcam)->bundle->dev), format)
> > > > > +#define gcam_err(gcam, format...)	dev_err(&((gcam)->bundle->dev), format)
> > > > >    static int gb_camera_operation_sync_flags(struct gb_connection *connection,
> > > > >    					  int type, unsigned int flags,
> > > > 
> > > 
> > > Thanks for the feedback, Alex!
> > > 
> > > I thought about refactoring it, but I feel it is worth keeping
> > > the macro around. It acts as an apdater between callers, who
> > > have 'gcam' and want to log and what the dynamic debug macros
> > > expect. Without it, the code gets pretty ugly.
> > 
> > Another idea would be to create a function:
> > 
> > struct device *gcam_dev(struct gb_camera *gcam)
> > {
> > 	return &gcam->bundle->dev;
> > }
> > 
> > 	dev_dbg(gcam_dev(gcam), "received metadata ...
> > 
> > (I don't know how to actually compile this code so I haven't tried it).
> 
> Yes, I prefer this over the original suggestion.  But
> even here the gcam_dev() function doesn't add all that
> much value; it saves four characters I guess.
> 
> Jackson, the basic principle that makes me say I don't
> like the wrapper macros is that the wrapper obscures
> the simple call(s) to dev_dbg(), etc.  If there was
> something you wanted to do every time--along with
> calling dev_dbg()--then maybe the wrapper would be
> helpful, but instead it simply hides the standard call.
> Better to have the code just use the functions kernel
> programmers recognize.
> 
> 					-Alex

Dan, Alex I think both of you are spot on.

I like the suggestion of adding 'gcam_dev()' as an accessor
function and directly calling to 'dev_*'. I'm busy this weekend
but will send out a new patch with this change next week.

Jackson

> > 
> > regards,
> > dan carpenter
>