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

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Date: Sat, 6 Apr 2024 12:09:03 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Jackson Chui <jacksonchui.qwerty@...il.com>
Cc: Alex Elder <elder@...e.org>, Johan Hovold <johan@...nel.org>,
	Alex Elder <elder@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	greybus-dev@...ts.linaro.org, linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: greybus: Clear up precedence for gcam logging
 macros

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@...il.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).

regards,
dan carpenter