linux-kernel - Re: [PATCH] mx3fb: Fix print format string

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Date:   Fri, 26 Aug 2016 23:28:35 -0400
From:   Oleg Drokin <green@...uxhacker.ru>
To:     Joe Perches <joe@...ches.com>
Cc:     Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        "Luis R. Rodriguez" <mcgrof@...e.com>, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mx3fb: Fix print format string


On Aug 26, 2016, at 11:18 PM, Joe Perches wrote:

> On Fri, 2016-08-26 at 23:05 -0400, Oleg Drokin wrote:
>> %ul was probably meant as %lu since the former would print
>> an unsigned value and a letter l.
>> 
>> But in fact the whole value we are printing in u32 anyway, so
>> we don't need the format to be long. Therefore just drop the l
>> altogether.
> []
>> Also do we really need 1000UL specification if we
>> cast to u32 anyway? Or should we drop away the cast instead?
>> Are pixelclocks over 4GHz possible here?
> 
> It's a debugging printk, it doesn't matter much.
> Why not use "%u kHz" and drop the "* 1000UL"?

I have no strong opinion on this since it's not my debugging code.

But XXX000l Hz makes zero sense either way.

>> diff --git a/drivers/video/fbdev/mx3fb.c b/drivers/video/fbdev/mx3fb.c
> []
>> @@ -845,7 +845,7 @@ static int __set_par(struct fb_info *fbi, bool lock)
>>  		if (fbi->var.sync & FB_SYNC_SHARP_MODE)
>>  			mode = IPU_PANEL_SHARP_TFT;
>>  
>> -		dev_dbg(fbi->device, "pixclock = %ul Hz\n",
>> +		dev_dbg(fbi->device, "pixclock = %u Hz\n",
>>  			(u32) (PICOS2KHZ(fbi->var.pixclock) * 1000UL));
>>  
>>  		if (sdc_init_panel(mx3fb, mode,
>>                                    (PICOS2KHZ(fbi->var.pixclock)) * 1000UL,

I guess it's printed like that to match sdc_init_panel argument exactly?