linux-kernel - Re: [PATCH v5 05/46] pwm: introduce the pwm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 12 Apr 2016 14:55:11 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	linux-pwm@...r.kernel.org,
	Mike Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>, linux-clk@...r.kernel.org,
	Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Kamil Debski <k.debski@...sung.com>, lm-sensors@...sensors.org,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	linux-leds@...r.kernel.org,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Chen-Yu Tsai <wens@...e.org>, linux-sunxi@...glegroups.com,
	Joachim Eastwood <manabian@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Heiko Stuebner <heiko@...ech.de>,
	linux-rockchip@...ts.infradead.org,
	Jingoo Han <jingoohan1@...il.com>,
	Lee Jones <lee.jones@...aro.org>, linux-fbdev@...r.kernel.org,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	linux-samsung-soc@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
	David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel@...ll.ch>,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Hartley Sweeten <hsweeten@...ionengravers.com>,
	Ryan Mallon <rmallon@...il.com>,
	Alexander Shiyan <shc_work@...l.ru>, Milo Kim <milo.kim@...com>
Subject: Re: [PATCH v5 05/46] pwm: introduce the pwm_args concept

On Tue, 12 Apr 2016 14:20:29 +0200
Thierry Reding <thierry.reding@...il.com> wrote:

> On Tue, Apr 12, 2016 at 02:04:12PM +0200, Boris Brezillon wrote:
> > On Tue, 12 Apr 2016 13:39:12 +0200
> > Thierry Reding <thierry.reding@...il.com> wrote:
> > 
> > > On Wed, Mar 30, 2016 at 10:03:28PM +0200, Boris Brezillon wrote:
> > > > Currently the PWM core mixes the current PWM state with the per-platform
> > > > reference config (specified through the PWM lookup table, DT definition or
> > > > directly hardcoded in PWM drivers).
> > > > 
> > > > Create a pwm_args struct to store this reference config, so that PWM users
> > > > can differentiate the current config from the reference one.
> > > > 
> > > > Patch all places where pwm->args should be initialized. We keep the
> > > > pwm_set_polarity/period() calls until all PWM users are patched to
> > > > use pwm_args instead of pwm_get_period/polarity().
> > > 
> > > Perhaps a helper would be useful? Something like:
> > > 
> > > 	static inline void
> > > 	pwm_apply_args(struct pwm_device *pwm, const struct pwm_args *args)
> > > 	{
> > > 		pwm_set_duty_cycle(pwm, args->duty_cycle);
> > > 		pwm_set_period(pwm, args->period);
> > > 	}
> > > 
> > > ? That would make it slightly easier to get rid of it again after all
> > > clients have been converted.
> > 
> > Sure. I'll add this helper.
> > 
> > > 
> > > With the exception of pwm-clps711x all of these args are set at of_xlate
> > > time (for DT) or from the lookup table in pwm_get() (for non-DT), so it
> > > might even be possible to move this call to the core, so that removal of
> > > it will be a one-liner.
> > 
> > Not sure I get that one. Some drivers are implementing their own
> > ->of_xlate() method, how would you get rid of this pwm_apply_args() in
> > those custom implementations?
> 
> I was proposing to have pwm_apply_args() called from the core.
> of_pwm_get() is where ->of_xlate() is called from, and the lookup table
> arguments would be applied in pwm_get(). Taking into account clps711x,
> which sets the arguments in ->request() it might be possible to simply
> call pwm_apply_args() from pwm_device_request(), since that's also
> called by all other request functions, even the legacy ones.
> 
> That said, the amount of code to modify isn't that large, so I'm fine if
> you want to keep sprinkling the calls across multiple files, especially
> since it's temporary.

No, I'm fine addressing that, but I just don't get where you'd get the
pwm_args to apply. Do you suggest to pass 'struct pwm_args *' to the
->of_xlate() and ->request() methods?

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com