Re: [Ksummit-discuss] Fwd: [TECH TOPIC] QR encoded oops for the kernel

[Josh Triplett <josh@joshtriplett.org>]

On Tue, May 13, 2014 at 09:44:26AM +0300, Teodora Băluţă wrote:
> On Mon, May 12, 2014 at 7:15 PM, Jason Cooper <jason@lakedaemon.net> wrote:
> > I'd like the URL to be valid (meaning base64 the compressed data) so
> > that we can get the data to the kernel.org server as easily as possible.
> > Making the app a requirement for reporting is too onerous for
> > non-developers.  I see no reason we can't link to (Open in/Install) it
> > on the webform though.
> 
> So from what I can understand, the QR code has an URL that has the
> base64 of the compressed Oops message. Right? I see three problems
> with this approach:
> 
> - base64 adds about 33% overhead (it's turning 3 octets into 4 encoded
> characters + padding). One issue with QR codes is that they have a
> limited amount of characters they can hold so that's why I do the
> compression in the first place

Putting base64-encoded data in a URL in a binary-format QR code with 8
bits per character does indeed waste quite a bit of space.  However, you
could put base32-encoded data into an alphanumeric-formatted QR code
with 5.5 bits per character, which would waste very little space.  (Or,
more efficiently but less conveniently, base40 or so.)

> - besides doing compression in a kernel that's had issues, you add the
> base64 encoding inside the kernel
> - you would still use a device with a camera (smartphone, tablet) to
> scan the QR from the framebuffer, so basically that means an app,
> right? What is the point of doing the URL validation inside the kernel
> when an app can do that? It doesn't add to the difficulty of sending
> the Oops to kernel.org (just one button away)

Many users will already have a QR-code scanning app installed, and such
apps always support loading URLs in a browser.

Another possibility to consider: current mobile browsers support the
HTML Media Capture API, which allows capturing an image from the camera
from within a file upload control.  Together with a bit of Javascript,
that would allow app-less oops capturing just by visiting a page and
using that page to capture the oops image.

- Josh Triplett