From: Mathieu Poirier <mathieu.poirier@linaro.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Chunyan Zhang <zhang.chunyan@linaro.org>,
Mike Leach <mike.leach@arm.com>,
Michael Williams <Michael.Williams@arm.com>,
Al Grant <al.grant@arm.com>, "Jeremiassen, Tor" <tor@ti.com>,
Nicolas GUION <nicolas.guion@st.com>,
Mark Brown <broonie@kernel.org>, Rob Herring <robh@kernel.org>,
Pratik Patel <pratikp@codeaurora.org>,
Jon Corbet <corbet@lwn.net>, Mark Rutland <mark.rutland@arm.com>,
Lyra Zhang <zhang.lyra@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
linux-api@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH V3 1/6] stm class: Add ioctl get_options interface
Date: Fri, 12 Feb 2016 11:33:17 -0700 [thread overview]
Message-ID: <CANLsYkzQTjROVX3K3NEE=GNg6QVKXLA9QDLVDe+W9eeDVwbgGQ@mail.gmail.com> (raw)
In-Reply-To: <87ziv62bzb.fsf@ashishki-desk.ger.corp.intel.com>
On 12 February 2016 at 08:18, Alexander Shishkin
<alexander.shishkin@linux.intel.com> wrote:
> Chunyan Zhang <zhang.chunyan@linaro.org> writes:
>
>> There is already an interface of set_options, but no get_options yet.
>> Before setting any options, one would may want to see the current
>> status of that option by means of get_options interface. This
>> interface has been used in CoreSight STM driver.
>
> I'm not sure I understand the reasoning behind this. If a userspace
> program opens a communication channel and wants to configure certain
> features on it, why does its choice depend on what has been configured
> for this channel previously? It can be anything at all. Most likely,
> it's either unconfigured or configured to its default values, but why
> does this matter for a new writer?
A client may wish to change the settings (invariant/guaranteed) it has
on a specific channel - it may even want to so do multiple times. The
idea behind introducing a get_options() was to probe the specific
settings of a channel before going a head with a new configuration.
In hindsight it may not be needed as a client should simply go ahead
and push down the configuration it wants.
>
> Regards,
> --
> Alex
next prev parent reply other threads:[~2016-02-12 18:33 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-06 11:04 [PATCH V3 0/6] Introduce CoreSight STM support Chunyan Zhang
2016-02-06 11:04 ` [PATCH V3 1/6] stm class: Add ioctl get_options interface Chunyan Zhang
2016-02-12 15:18 ` Alexander Shishkin
2016-02-12 18:33 ` Mathieu Poirier [this message]
2016-02-06 11:04 ` [PATCH V3 2/6] stm class: Support devices with multiple instances Chunyan Zhang
2016-02-06 11:04 ` [PATCH V3 3/6] stm class: provision for statically assigned masterIDs Chunyan Zhang
2016-02-06 11:04 ` [PATCH V3 4/6] Documentations: Add explanations of the case for non-configurable masters Chunyan Zhang
2016-02-06 11:04 ` [PATCH V3 5/6] coresight-stm: Bindings for System Trace Macrocell Chunyan Zhang
2016-02-06 11:04 ` [PATCH V3 6/6] coresight-stm: adding driver for CoreSight STM component Chunyan Zhang
2016-02-11 16:59 ` Mathieu Poirier
2016-02-12 14:55 ` Michael Williams
2016-02-12 18:24 ` Mathieu Poirier
2016-02-17 3:18 ` Chunyan Zhang
2016-02-17 12:08 ` Michael Williams
2016-02-17 3:49 ` Chunyan Zhang
2016-02-12 15:28 ` Alexander Shishkin
2016-02-12 19:02 ` Mathieu Poirier
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