Re: [RFC] QR encoding for Oops messages

[Jason Cooper]

On Sun, Mar 30, 2014 at 12:17:17PM +0200, Levente Kurusa wrote:
> Hi all,
> 
> (sorry for the late reply, looks like this mail has ran away from my clients)
> 
> 2014-03-23 20:38 GMT+01:00 Jason Cooper <jason@xxxxxxxxxxxxxx>:
> > All,
> >
> > On Sat, Mar 22, 2014 at 08:20:01PM +0200, Teodora BÄluÅÄ wrote:
> >> On Sat, Mar 22, 2014 at 7:09 PM, Levente Kurusa <levex@xxxxxxxxx> wrote:
> >> > On 03/21/2014 02:28 PM, Jason Cooper wrote:
> > ...
> >> >> I would definitely like to see the QR output incorporated into a
> >> >> kernel.org url.  That would remove the need for installing another app,
> >> >> and would ease bug reporting.
> >> >
> >> > I still struggle to understand how could that be done. We can encode the
> >> > QR code as ASCII. Okay, that's fine, however it is very long. Encoding
> >> > 'Unable to handle kernel paging request at 0000000f' gave a 449 character
> >> > long sequence with very strange characters [0]. We should try to shorten
> >> > it, imho. Not sure how to do that though.
> >
> > The man page for qrencode says you can have up to 4000 characters in a
> > qrcode.  However, I've seen readers have trouble with a 2048bit ascii
> > armored PGP public key (3929 characters).
> >
> > I grabbed a random oops from oops.kernel.org, it weighed in at 1544
> > bytes, not too bad.  I then did:
> >
> > $ echo "https://oops.kernel.org/?qr=`cat oops.txt | gzip -9 | base64 -wrap=0`" | wc -c
> > 993
> 
> I did the same with another OOPS and it had 1953 characters. That's quite a big
> a big difference! :-)
> 
> I created a QR image from the URL then, and it was 147x147, which is
> pretty small.
> It took me quite a long time to make my phone recognize it, but it
> worked nicely.
> 
> Result of work is in this directory:
> 
> http://levex.fedorapeople.org/kernel/qr/

nice!

> > The benefit of a url is that any QR reader can automagically report an
> > oops.  While a specific app could parse the URL/oops locally if the
> > user desires.
> >
> >> it misses the point of having a QR code in the first place. The way I
> >> see it, having a QR decoder app installed that can do an offline
> >> decoding is a less greater effort than popping out a browser on the
> >> machine you're working on.
> >
> > I think you're selling the advantage of the QR code short.  Automated
> > reporting (via the url) is a _huge_ plus.  The app you conceive of could
> > still parse it in place if the user desires.
> >
> > My point for the URL isn't to use the internet/server to automate oops
> > parsing for the user.  Rather it's to make it easy to report oopses to
> > developers.  While still preserving the ability of your app to parse it
> > for the user.
> 
> Ah I see now. oops.kernel.org/?qr=<QR> would simply parse the
> base64'd+gzip'd oops message and then report it.

If you mean the server behind oops.k.o would parse it, then yes.  No
special app should be required other than a QR code scanner for the
usecase of reporting oopses to developers.

> Now I guess we need to think how to make it work without a
> framebuffer. I already suggested using the ASCII characters,
> but seeing the resolution of this QR code for example (147x147),
> made me realize that we can't shuffle that into a 80x25 textmode
> display. Any ideas how to fix that or should we just simply depend
> on a framebuffer being present?

I think depending on the framebuffer being present (via kconfig) is
sane.  Folks running old systems know what they're in for, like missing
shiny new features. ;-)

thx,

Jason.
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