linux-kernel - Re: [PATCH v3 2/4] pwm: rockchip: Allow polarity invert on rk3288

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Date:	Thu, 21 Aug 2014 08:40:27 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Doug Anderson <dianders@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Caesar Wang <caesar.wang@...k-chips.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Eddie Cai <eddie.cai@...k-chips.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	linux-pwm <linux-pwm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, hpa@...or.com
Subject: Re: [PATCH v3 2/4] pwm: rockchip: Allow polarity invert on rk3288

On Wed, Aug 20, 2014 at 02:29:17PM -0500, Dmitry Torokhov wrote:
> On August 20, 2014 1:54:11 PM CDT, Doug Anderson <dianders@...omium.org> wrote:
> >On Wed, Aug 20, 2014 at 3:04 AM, Thierry Reding
> ><thierry.reding@...il.com> wrote:
> >> On Tue, Aug 19, 2014 at 09:07:54AM -0700, Doug Anderson wrote:
> >>> The rk3288 has the ability to invert 
> >>> +     struct rockchip_pwm_chip *pc = to_rockchip_pwm_chip(chip);
> >>> +
> >>> +     if (!pc->data->has_invert)
> >>> +             return -ENOSYS;
> >>> +
> 
> At the kernel summit hpa also mentioned that ENOSYS should only be
> used for missing syscalls. Not sure what error code would suit better
> here though...

I'd be interested in the rationale why ENOSYS shouldn't be used within
the kernel. As long as it doesn't leak to userspace where it could
possibly confuse applications I don't see any harm in using it.

Thierry

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