linux-kernel - Re: [RFC] dynamic_debug: introduce debug_hex

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Message-ID: <1367870.EsNpLZfRqp@lx-vladimir>
Date:	Sun, 18 Nov 2012 15:51:26 +0200
From:	Vladimir Kondratiev <vkondrat@....qualcomm.com>
To:	Joe Perches <joe@...ches.com>
Cc:	"John W . Linville" <linville@...driver.com>,
	Johannes Berg <johannes@...solutions.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-wireless@...r.kernel.org,
	"Luis R . Rodriguez" <rodrigue@....qualcomm.com>,
	Jason Baron <jbaron@...hat.com>,
	Jim Cromie <jim.cromie@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] dynamic_debug: introduce debug_hex_dump()

On Sunday, November 18, 2012 11:47:58 AM Vladimir Kondratiev wrote:
> On Wednesday, November 14, 2012 07:27:47 PM Vladimir Kondratiev wrote:
> > +#define dynamic_hex_dump(prefix_str, prefix_type, rowsize,     \
> > +                        groupsize, buf, len, ascii)            \
> > +do {                                                           \
> > +       DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, prefix_str);  \
> > +       if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT))  \
> > +               print_hex_dump(KERN_DEBUG, prefix_str,          \
> > +                              prefix_type, rowsize, groupsize, \
> > +                              buf, len, ascii);                \
> > +} while (0)
> 
> There is some problem with the code above. There are existing drivers
> that use print_hex_dump_bytes() with the prefix_str built dynamically,
> like this (see drivers/tty/ipwireless/hardware.c:362)
> 
> static void dump_data_bytes(const char *type, const unsigned char *data,
> 			    unsigned length)
> {
> 	char prefix[56];
> 
> 	sprintf(prefix, IPWIRELESS_PCCARD_NAME ": %s %s ",
> 			type, data_type(data, length));
> 	print_hex_dump_bytes(prefix, 0, (void *)data,
> 			length < DUMP_MAX_BYTES ? length : DUMP_MAX_BYTES);
> }
> 
> In this case, prefix_str is not constant, and this solution will not
> work.
> 
> I see 2 drivers that use dynamic prefix:
> 
> - mentioned above drivers/tty/ipwireless/hardware.c
> - drivers/isdn/hardware/mISDN/
> 
> I see several options:
> 
> 1) require prefix_str to be constant. Patch code mentioned. For example,
> code above may reads:
> 
> static void dump_data_bytes(const char *type, const unsigned char *data,
> 			    unsigned length)
> {
> 	pr_debug(IPWIRELESS_PCCARD_NAME ": %s %s\n",
> 			type, data_type(data, length));
> 	print_hex_dump_bytes(IPWIRELESS_PCCARD_NAME, 0, (void *)data,
> 			length < DUMP_MAX_BYTES ? length : DUMP_MAX_BYTES);
> }
> 
> 2) introduce fixed format string in DEFINE_DYNAMIC_DEBUG_METADATA, like
> 
> DEFINE_DYNAMIC_DEBUG_METADATA((descriptor, "hexdump");
> 
> 3) remove print_hex_dump_bytes from this patch
> 
> I think 1) is the best, opinions?
> 
> Thanks, Vladimir

In case of option 1), patches follows. Note there is change in the initial patch as well (I forgot to exclude print_hex_dump_bytes() from compilation in hexdump.c. Please, comment.


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