Thank you Simon for your reply. I understand that it is very dangerous to give full access to the whole memory. My application runs on a Raspberry Pi and controls a LED stripe (such as https://www.adafruit.com/product/2294 or https://www.sparkfun.com/ products/13304). These devices (based in WS281X chips) require a very accurate "real-time" signal that is hard to produce on a system with an operating system (It is easier to use it with an Arduino).
For the Raspberry Pi, we can use the popular library from Jeremy Garff ( https://github.com/jgarff/rpi_ws281x). This library uses the DMA coupled with the PWM to generate the accurate signal. I don't know in detail how does the interface works and why it needs to write directly to /dev/mem. I'm just using it with a golang wrapper around it. My code is available on gitlab (https://gitlab.com/telecom-tower/tower) and the snap is automatically built using gitlab-CI. You can see a picture of the system (and the current message) on https://telecom-tower.tk/. Best regards, █ Jacques On 10 November 2016 at 09:33, Simon Fels <simon.f...@canonical.com> wrote: > On 09.11.2016 21:25, Jacques Supcik wrote: > > Thank you Oliver for your constructive feedback. > > > > I like the idea of a "mailbox-device" and I will open a bug in the > > whishlist of snappy. > > > > My snap needs also write access to "/dev/mem": > > > > = AppArmor = > > Time: Nov 9 19:09:52 > > Log: apparmor="ALLOWED" operation="open" > > profile="snap.telecom-tower.daemon" name="/dev/mem" pid=3643 > > comm="tower" requested_mask="wr" denied_mask="wr" fsuid=0 ouid=0 > > File: /dev/mem (write) > > > > Should this also be addressed by the "mailbox-device" interface or > > should I fill another bug for a "physical-memory" interface? Or do you > > have an idea for a better name? Or is there already something available > > for accessing /dev/mem? > > This would be definitely a different interface but the more interesting > question is why your app needs access to /dev/mem. That would give blind > access to the whole system memory space which is a highly privileged > operation I would say not many applications will need or even get > because of the obvious access to everything on the system. > > Can you elaborate a bit more on what your application is doing with > /dev/mem and why it needs access to the full system memory? > > regards, > Simon > > > > > -- > Snapcraft mailing list > Snapcraft@lists.snapcraft.io > Modify settings or unsubscribe at: https://lists.ubuntu.com/ > mailman/listinfo/snapcraft >
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