Subject: Re: [PATCH] lightnvm: work around 32-bit built error
To: Arnd Bergmann <arnd@arndb.de>, Matias Bjorling <mb@lightnvm.io>
References: <4925999.tpkPGVQaeU@wuerfel>
CC: <linux-kernel@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>
From: Jens Axboe <axboe@fb.com>
Message-ID: <5638D1F0.7060406@fb.com>
Date: Tue, 3 Nov 2015 08:25:36 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.3.0
MIME-Version: 1.0
In-Reply-To: <4925999.tpkPGVQaeU@wuerfel>
Content-Type: text/plain; charset="windows-1252"; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1310
Lines: 31

On 11/03/2015 06:53 AM, Arnd Bergmann wrote:
> The newly added lightnvm incorrectly uses a sector_t variable to
> represent a data structure with fixed length bit fields, which breaks
> when sector_t is configured to be 32-bit:
>
> In file included from ../drivers/lightnvm/core.c:29:0:
> /include/linux/lightnvm.h:143:4: error: width of 'resved' exceeds its type
>      sector_t resved  : 36;
> include/linux/lightnvm.h: In function 'ppa_set_empty':
> /include/linux/lightnvm.h:120:20: warning: large integer implicitly truncated to unsigned type [-Woverflow]
>   #define ADDR_EMPTY (~0ULL)

Thanks Arnd, Matias sent another variant yesterday that changes this to 
u64 as well.

> This patch resolves the build error, but does not address the fact that
> bit fields are not reliable in data structures that are interpreted
> by firmware on another architecture. If the layout is meant to be
> stable, the bit fields should be replaced with explicit calculations.

Matias? Are these every stored and read back, potentially on a different 
machine?

-- 
Jens Axboe

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/