From mboxrd@z Thu Jan  1 00:00:00 1970
From: Timur Tabi <timur@freescale.com>
Date: Tue, 30 Mar 2010 17:32:59 -0500
Subject: [U-Boot] [PATCH] fix print_size printing fractional gigabyte
 numbers on 32-bit platforms
In-Reply-To: <4BB278F1.40705@freescale.com>
References: <1269985996-13130-1-git-send-email-timur@freescale.com>
	<4BB275B7.90509@freescale.com> <4BB2766F.9070808@freescale.com>
	<4BB278F1.40705@freescale.com>
Message-ID: <4BB27C1B.8000301@freescale.com>
List-Id: <u-boot.lists.denx.de>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: u-boot@lists.denx.de

Scott Wood wrote:

> It would make the 10 * (...) product 64-bit regardless of phys_size_t, 
> without changing the function signature (overflow is an internal 
> implementation detail).

You are right that (n * d) is evaluated as a 32-bit integer:

	print_size(5905580032)= 6.35 GB

However, changing "10" to "10ULL" does not fix this.  I think this is because we are both expecting integer sizes to commute across arithmetic operations.  That is, I assumed that:

	u64 - (u32 * u32) 

would be treated as 

	u64 - ((u64)u32 * u32) 

And you assumed that 

	u64 * (u32 - u32)

would be treated as

	u64 * (u32 - (u64) u32)

Both appear to be wrong.  If we want to treat (n * d) as a u64, we need to be explicit.  Casting "(n * d)" to a u64 just doesn't work.  We have to cast (or make) either 'n' or 'd' to a u64.

I think the simplest approach is make 'd' into a u64.

-- 
Timur Tabi
Linux kernel developer at Freescale