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From: Matthias Kaehlcke <mka@chromium.org>
To: Chanwoo Choi <cw00.choi@samsung.com>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Brian Norris <briannorris@chromium.org>,
	Douglas Anderson <dianders@chromium.org>,
	Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Lee Jones <lee.jones@linaro.org>,
	Benson Leung <bleung@chromium.org>,
	Olof Johansson <olof@lixom.net>
Subject: Re: [PATCH v5 07/12] PM / devfreq: export devfreq_class
Date: Fri, 6 Jul 2018 11:09:23 -0700	[thread overview]
Message-ID: <20180706180923.GH129942@google.com> (raw)
In-Reply-To: <5B3C5B78.6020401@samsung.com>

Hi,

On Wed, Jul 04, 2018 at 02:30:32PM +0900, Chanwoo Choi wrote:

> I didn't see any framework which exporting the class instance.
> It is very dangerous. Unknown device drivers is able to reset
> the 'devfreq_class' instance. I can't agree this approach.

While I agree that it is potential dangerous it is actually a common
practice to export the class:

grep "extern struct class " include/linux/ -R
include/linux/rio.h:extern struct class rio_mport_class;
include/linux/tty.h:extern struct class *tty_class;
include/linux/fb.h:extern struct class *fb_class;
include/linux/ide.h:extern struct class *ide_port_class;
include/linux/device.h:extern struct class * __must_check __class_create(struct module *owner,
include/linux/devfreq.h:extern struct class *devfreq_class;
include/linux/switchtec.h:extern struct class *switchtec_class;
include/linux/input.h:extern struct class input_class;
include/linux/genhd.h:extern struct class block_class;
include/linux/power_supply.h:extern struct class *power_supply_class;
include/linux/rtc.h:extern struct class *rtc_class;

struct class_interface and class_interface_register() would be
pointless without exported classes.

My understanding is that the kernel is often lax on encapsulation and
exposes private/delicate data pragmatically within the kernel when
needed because "the kernel trusts itself".

Thanks

Matthias

  reply	other threads:[~2018-07-06 18:09 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-03 23:46 [PATCH v5 00/12] Add throttler driver for non-thermal throttling Matthias Kaehlcke
2018-07-03 23:46 ` [PATCH v5 01/12] PM / devfreq: Init user limits from OPP limits, not viceversa Matthias Kaehlcke
2018-07-03 23:46 ` [PATCH v5 02/12] PM / devfreq: Fix handling of min/max_freq == 0 Matthias Kaehlcke
2018-07-04  2:20   ` Chanwoo Choi
2018-07-06 16:36     ` Matthias Kaehlcke
2018-07-12  8:34       ` Chanwoo Choi
2018-07-03 23:46 ` [PATCH v5 03/12] PM / devfreq: Don't adjust to user limits in governors Matthias Kaehlcke
2018-07-04  2:27   ` Chanwoo Choi
2018-08-02 23:36   ` Matthias Kaehlcke
2018-08-03  0:03     ` Chanwoo Choi
2018-08-03  0:24       ` Matthias Kaehlcke
2018-08-03  0:43         ` Chanwoo Choi
2018-07-03 23:46 ` [PATCH v5 04/12] PM / devfreq: Add struct devfreq_policy Matthias Kaehlcke
2018-07-04  2:51   ` Chanwoo Choi
2018-07-06 17:07     ` Matthias Kaehlcke
2018-07-12  8:38       ` Chanwoo Choi
2018-08-03  0:04         ` Chanwoo Choi
2018-07-03 23:46 ` [PATCH v5 05/12] PM / devfreq: Add support for policy notifiers Matthias Kaehlcke
2018-07-04  6:41   ` Chanwoo Choi
2018-07-06 17:53     ` Matthias Kaehlcke
2018-07-12  8:44       ` Chanwoo Choi
2018-07-16 17:50         ` Matthias Kaehlcke
2018-07-31 19:39           ` Matthias Kaehlcke
2018-08-01  1:22             ` Chanwoo Choi
2018-08-01 17:08               ` Matthias Kaehlcke
2018-08-02  1:58                 ` Chanwoo Choi
2018-08-02 23:13                   ` Matthias Kaehlcke
2018-08-02 23:48                     ` Matthias Kaehlcke
2018-08-03  0:14                       ` Chanwoo Choi
2018-08-06 19:21                         ` Matthias Kaehlcke
2018-08-06 22:31                           ` Chanwoo Choi
2018-08-06 22:50                             ` Chanwoo Choi
2018-08-07  0:23                             ` Matthias Kaehlcke
2018-08-07  1:35                               ` Chanwoo Choi
2018-08-07 22:34                                 ` Matthias Kaehlcke
2018-08-02 23:56                     ` Chanwoo Choi
2018-08-06 18:46                       ` Matthias Kaehlcke
2018-08-06 22:16                         ` Chanwoo Choi
2018-07-03 23:46 ` [PATCH v5 06/12] PM / devfreq: Make update_devfreq() public Matthias Kaehlcke
2018-08-01  8:32   ` Chanwoo Choi
2018-07-03 23:47 ` [PATCH v5 07/12] PM / devfreq: export devfreq_class Matthias Kaehlcke
2018-07-04  5:30   ` Chanwoo Choi
2018-07-06 18:09     ` Matthias Kaehlcke [this message]
2018-07-12  9:08       ` Chanwoo Choi
2018-07-16 19:41         ` Matthias Kaehlcke
2018-07-31 19:29           ` Matthias Kaehlcke
2018-08-01  8:18             ` Chanwoo Choi
2018-08-01 17:18               ` Matthias Kaehlcke
2018-07-03 23:47 ` [PATCH v5 08/12] cpufreq: Add stub for cpufreq_update_policy() Matthias Kaehlcke
2018-07-04 10:41   ` Rafael J. Wysocki
2018-07-10 22:24     ` Matthias Kaehlcke
2018-07-04 10:44   ` Viresh Kumar
2018-07-03 23:47 ` [PATCH v5 09/12] dt-bindings: misc: add bindings for throttler Matthias Kaehlcke
2018-07-04 10:00   ` Viresh Kumar
2018-07-04 10:00     ` Viresh Kumar
2018-08-01  8:27   ` Chanwoo Choi
2018-08-01 17:39     ` Matthias Kaehlcke
2018-07-03 23:47 ` [PATCH v5 10/12] misc: throttler: Add core support for non-thermal throttling Matthias Kaehlcke
2018-07-03 23:47 ` [PATCH v5 11/12] misc: throttler: Add Chrome OS EC throttler Matthias Kaehlcke
2018-07-03 23:47 ` [PATCH v5 12/12] mfd: cros_ec: Add throttler sub-device Matthias Kaehlcke
2018-07-04  7:59   ` Lee Jones
     [not found] ` <CGME20180703234727epcas3p1b9f4a41b1f1714c8c059100d46b816dd@epcms1p5>
2018-07-04  2:24   ` [PATCH v5 01/12] PM / devfreq: Init user limits from OPP limits, not viceversa MyungJoo Ham
2018-07-04  2:24     ` MyungJoo Ham

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