linux-kernel - Re: [PATCH] Input - elantech: fix debug dump of the current packet

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Date:	Thu, 28 Jul 2016 11:54:09 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input - elantech: fix debug dump of the current packet

On Thu, Jul 28, 2016 at 11:49:57AM -0700, Joe Perches wrote:
> On Thu, 2016-07-28 at 11:40 -0700, Dmitry Torokhov wrote:
> > On Thu, Jul 28, 2016 at 11:30:56AM -0700, Joe Perches wrote:
> > > 
> > > On Thu, 2016-07-28 at 11:58 +0200, Benjamin Tissoires wrote:
> > > > 
> > > > The use of mixed psmouse_printk() and printk creates 2 lines in the log,
> > > > while the use of %*ph solves everything.
> > > > 
> > > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > > > ---
> > > >  drivers/input/mouse/elantech.c | 8 ++------
> > > >  1 file changed, 2 insertions(+), 6 deletions(-)
> > > > 
> > > > diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
> > > > index 615d23e..3461d04 100644
> > > > --- a/drivers/input/mouse/elantech.c
> > > > +++ b/drivers/input/mouse/elantech.c
> > > > @@ -222,12 +222,8 @@ static int elantech_write_reg(struct psmouse *psmouse, unsigned char reg,
> > > >   */
> > > >  static void elantech_packet_dump(struct psmouse *psmouse)
> > > >  {
> > > > -	int	i;
> > > > -
> > > > -	psmouse_printk(KERN_DEBUG, psmouse, "PS/2 packet [");
> > > > -	for (i = 0; i < psmouse->pktsize; i++)
> > > > -		printk("%s0x%02x ", i ? ", " : " ", psmouse->packet[i]);
> > > > -	printk("]\n");
> > > > +	psmouse_printk(KERN_DEBUG, psmouse, "PS/2 packet [%*ph]",
> > > > +		       psmouse->pktsize, psmouse->packet);
> > > >  }
> > > >  
> > > >  /*
> > > This should add a newline "\n" format termination but
> > I added it, thanks for alerting me.
> > 
> > > 
> > > how does the original produce multiple lines of output?
> > > 
> > > It looks more like psmouse_printk should be removed altogether
> > > and dev_debug should be used instead.
> > That does not produce output by default whereas elantech driver uses
> > elantech_packet_dump() to drop unexpected packets.
> 
> So use dev_printk(KERN_DEBUG, etc...

#define psmouse_printk(level, psmouse, format, ...)	\
	dev_printk(level,				\
		   &(psmouse)->ps2dev.serio->dev,	\
		   psmouse_fmt(format), ##__VA_ARGS__)

I want to see current protocol module in th eoutput and I do not want to
write "&(psmouse)->ps2dev.serio->dev" all the time.

> 
> 
> But I still don't see a mechanism for the original code to be
> emitted on multiple lines.

Message from another driver snuck in?

> 
> How long is the longest packet?
> 
> This might truncate it.

No, buffer is 8 bytes.

> 
> Should this be ratelimited?

So far there wasn't a need.

-- 
Dmitry