From: "H. Peter Anvin" <hpa@zytor.com>
Message-ID: <1085.62.20.197.108.1058711609.squirrel@www.zytor.com>
Date: Sun, 20 Jul 2003 07:33:29 -0700 (PDT)
Subject: Re: [PATCH] print_dev_t for 2.6.0-test1-mm
To: <aebr@win.tue.nl>
In-Reply-To: <20030717124323.B2302@pclin040.win.tue.nl>
References: <20030716184609.GA1913@kroah.com>
        <20030716213451.GA1964@win.tue.nl>
        <20030716143902.4b26be70.akpm@osdl.org>
        <20030716222015.GB1964@win.tue.nl>
        <200307170300.UAA24096@cesium.transmeta.com>
        <20030717124323.B2302@pclin040.win.tue.nl>
Importance: Normal
Cc: <hpa@zytor.com>, <linux-kernel@vger.kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7BIT
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1245
Lines: 41

> On Wed, Jul 16, 2003 at 07:54:36PM -0700, H. Peter Anvin wrote:
>
>> > 16-bit only: 8:8, otherwise 32-bit only: 16:16, otherwise 32:32.
>>
>> I would still recommend the arrangement for 64-bit dev_t that I posted
>> a while ago:
>>
>> dev_t<63:40> := major<31:8>
>> dev_t<39:16> := minor<31:8>
>> dev_t<15:8>  := major<7:0>
>> dev_t<7:0>   := minor<7:0>
>
> Yes, but we we also need to handle 32-bit dev_t incarnations.
>
>> If you want, you can even make it 32-bit-friendly, although it makes
>> it more complex; for example, this version would implement 32-bit with
>> a 12:20 split:
>>
>> dev_t<63:44> := major<31:12>
>> dev_t<43:32> := minor<31:20>
>> dev_t<31:28> := major<11:8>
>> dev_t<27:16> := minor<19:8>
>> dev_t<15:8>  := major<7:0>
>> dev_t<7:0>   := minor<7:0>
>
> Too messy. But you are right - no conditionals involved.

It's only necessary, though, if we require that dev32_t is a pure
truncation of dev_t, which is nice but not necessary.

No aliasing is a *very* good thing.


-
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/