From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Lechner Subject: Re: [v7,03/10] docs: Add Generic Counter interface documentation Date: Mon, 2 Jul 2018 14:37:53 -0500 Message-ID: References: <7606bdc53c26c332b2bbff0f865380fb0e874b56.1529607879.git.vilhelm.gray@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <7606bdc53c26c332b2bbff0f865380fb0e874b56.1529607879.git.vilhelm.gray@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: William Breathitt Gray , gregkh@linuxfoundation.org Cc: jic23@kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, fabrice.gasnier@st.com, benjamin.gaignard@st.com, robh+dt@kernel.org, knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net, mark.rutland@arm.com List-Id: devicetree@vger.kernel.org On 06/21/2018 04:07 PM, William Breathitt Gray wrote: > +Userspace Interface > +=================== > + > +Several sysfs attributes are generated by the Generic Counter interface, > +and reside under the /sys/bus/counter/devices/counterX directory, where > +counterX refers to the respective counter device. Please see > +Documentation/ABI/testing/sys-bus-counter-generic-sysfs for detailed > +information on each Generic Counter interface sysfs attribute. > + > +Through these sysfs attributes, programs and scripts may interact with > +the Generic Counter paradigm Counts, Signals, and Synapses of respective > +counter devices. > + Have you considered a character device in addition to the sysfs interface? I basically have many of the same concerns that resulted in a char dev for gpio[1]. - With sysfs, you *can* technically poll for events, but then you have to seek and read or re-open the file. - File permissions are annoying if you want a non root user to be able to use the device. - A single program can't claim exclusive access to a device. - There is no automatic cleanup if a userspace program accessing the device crashes. [1]: https://www.elinux.org/images/7/74/Elce2017_new_GPIO_interface.pdf