linux-kernel - Re: [PATCHv6 1/2] add basic register-field manipulation macros

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Date:	Wed, 17 Aug 2016 10:16:08 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:	Kalle Valo <kvalo@...eaurora.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	David Miller <davem@...emloft.net>,
	Linux Wireless List <linux-wireless@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dinan.gunawardena@...ronome.com
Subject: Re: [PATCHv6 1/2] add basic register-field manipulation macros

On Wed, Aug 17, 2016 at 10:11 AM, Jakub Kicinski
<jakub.kicinski@...ronome.com> wrote:
> On Wed, 17 Aug 2016 09:33:26 -0700, Linus Torvalds wrote:
>>
>> I'm not a huge fan, since the interface fundamentally seems to be
>> oddly designed (why pass in the mask rather than "start bit +
>> length"?).
>
> Would that not require start and length to have separate defines?

Yeah.

> I assume doing:
>
>     #define REG_BLA_FIELD_FOO  3, 4
>     val = FIELD_GET(REG_BLA_FIELD_FOO, reg);
>
> is not acceptable.  Attempts to define a single value brought us to the
> shifted mask.

Agreed. Maybe the mask with the complexity to then undo it (at compile
time) is the better approach.

            Linus