linux-kernel - Re: [PATCH] staging: gdm72xx: conditionally compile debug code

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Message-ID: <20140716221034.GB716@kroah.com>
Date:	Wed, 16 Jul 2014 15:10:34 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Michalis Pappas <mpappas@...tmail.fm>
Cc:	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: gdm72xx: conditionally compile debug code

On Wed, Jul 16, 2014 at 11:03:06PM +0100, Michalis Pappas wrote:
> On 07/16/2014 09:50 PM, Greg KH wrote:
> > On Wed, Jul 16, 2014 at 09:40:18PM +0100, Michalis Pappas wrote:
> >> On 07/09/2014 07:51 PM, Greg KH wrote:
> >>>> diff --git a/drivers/staging/gdm72xx/gdm_sdio.c b/drivers/staging/gdm72xx/gdm_sdio.c
> >>>> index 9d2de6f..914fd75 100644
> >>>> --- a/drivers/staging/gdm72xx/gdm_sdio.c
> >>>> +++ b/drivers/staging/gdm72xx/gdm_sdio.c
> >>>> @@ -280,9 +280,11 @@ static void send_sdu(struct sdio_func *func, struct tx_cxt *tx)
> >>>>  
> >>>>  	spin_unlock_irqrestore(&tx->lock, flags);
> >>>>  
> >>>> +	#if defined(GDM72xx_DEBUG)
> >>>>  	print_hex_dump_debug("sdio_send: ", DUMP_PREFIX_NONE, 16, 1,
> >>>>  			     tx->sdu_buf + TYPE_A_HEADER_SIZE,
> >>>>  			     aggr_len - TYPE_A_HEADER_SIZE, false);
> >>>> +	#endif
> >>>
> >>> This should be moved to use dev_dbg(), along with the other calls to
> >>> this function in this file.
> >>>
> >>
> >> But dev_dbg() gets eventually to be printk(), which cannot print the
> >> buffer, so using print_hex_dump_debug() seems to be correct for this
> >> case, no?
> > 
> > No, you don't want to print the message unless debugging is enabled, and
> > dev_dbg() uses the proper in-kernel dynamic debug infrastructure.  There
> > should never be a separate config option for debugging a driver, that
> > ensures that no user will ever be able to help you out with it.
> > 
> > So delete the ifdef stuff, and the config option, and just use the
> > proper in-kernel infrastructure for this.
> > 
> > thanks,
> > 
> > greg k-h
> > 
> 
> Ok, I agree on the ifdef stuff. My question was regarding your
> suggestion above to replace print_hex_debug() with dev_dbg()

You want the device name/id/label to show up as well, that is why you
should use the dev_dbg() version, print_hex_dump() does not take a
struct device *, so the user has no idea what device this data was
coming from.

thanks,

greg k-h
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