netdev - RE: [PATCH] ethernet: e1000e: define lat

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Date:	Wed, 8 Apr 2015 09:40:49 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	"'yanjiang.jin@...driver.com'" <yanjiang.jin@...driver.com>,
	"bruce.w.allan@...el.com" <bruce.w.allan@...el.com>
CC:	"jeffrey.t.kirsher@...el.com" <jeffrey.t.kirsher@...el.com>,
	"jesse.brandeburg@...el.com" <jesse.brandeburg@...el.com>,
	"carolyn.wyborny@...el.com" <carolyn.wyborny@...el.com>,
	"donald.c.skidmore@...el.com" <donald.c.skidmore@...el.com>,
	"gregory.v.rose@...el.com" <gregory.v.rose@...el.com>,
	"matthew.vick@...el.com" <matthew.vick@...el.com>,
	"john.ronciak@...el.com" <john.ronciak@...el.com>,
	"mitch.a.williams@...el.com" <mitch.a.williams@...el.com>,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>,
	"linux.nics@...el.com" <linux.nics@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jinyanjiang@...il.com" <jinyanjiang@...il.com>
Subject: RE: [PATCH] ethernet: e1000e: define lat_ns as u64 instead of s64

From: yanjiang.jin@...driver.com
> Sent: 03 April 2015 10:18
> From: Yanjiang Jin <yanjiang.jin@...driver.com>
> 
> do_div() expects the type of "n" to be uint64_t, define "lat_ns" as u64 to
> avoid the below warning, also update its correlative operations and data.
> 
> In file included from ./arch/powerpc/include/asm/div64.h:1:0,
>                  from include/linux/kernel.h:124,
>                  from include/linux/list.h:8,
>                  from include/linux/timer.h:4,
>                  from drivers/net/ethernet/intel/e1000e/e1000.h:29,
>                  from drivers/net/ethernet/intel/e1000e/ich8lan.c:59:
> drivers/net/ethernet/intel/e1000e/ich8lan.c: In function 'e1000_platform_pm_pch_lpt':
> include/asm-generic/div64.h:43:28: warning: comparison of distinct pointer types lacks a cast [enabled
> by default]
>   (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
>                             ^
> drivers/net/ethernet/intel/e1000e/ich8lan.c:1016:4: note: in expansion of macro 'do_div'
>     do_div(lat_ns, speed);
> 
> Signed-off-by: Yanjiang Jin <yanjiang.jin@...driver.com>
> ---
>  drivers/net/ethernet/intel/e1000e/ich8lan.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
> index 48b74a5..baab58b 100644
> --- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
> +++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c
> @@ -982,8 +982,8 @@ static s32 e1000_platform_pm_pch_lpt(struct e1000_hw *hw, bool link)
>  		u16 speed, duplex, scale = 0;
>  		u16 max_snoop, max_nosnoop;
>  		u16 max_ltr_enc;	/* max LTR latency encoded */
> -		s64 lat_ns;	/* latency (ns) */
> -		s64 value;
> +		u64 lat_ns;	/* latency (ns) */
> +		u64 value;
>  		u32 rxa;
> 
>  		if (!hw->adapter->max_frame_size) {
> @@ -1008,8 +1008,8 @@ static s32 e1000_platform_pm_pch_lpt(struct e1000_hw *hw, bool link)
>  		 * 2^25*(2^10-1) ns.  The scale is encoded as 0=2^0ns,
>  		 * 1=2^5ns, 2=2^10ns,...5=2^25ns.
>  		 */
> -		lat_ns = ((s64)rxa * 1024 -
> -			  (2 * (s64)hw->adapter->max_frame_size)) * 8 * 1000;
> +		lat_ns = ((u64)rxa * 1024 -
> +			  (2 * (u64)hw->adapter->max_frame_size)) * 8 * 1000;
>  		if (lat_ns < 0)
>  			lat_ns = 0;

The above change cannot be correct.
You should be getting another error for testing an unsigned value be less than 0.

So I presume this wasn't even tested.

	David

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