[Bluez-devel] Bluez DBUS API usuability regarding end user experience

Fabien Chevalier
2007-10-25T18:23:31Z

[-- Attachment #1: Type: text/plain, Size: 2536 bytes --]

Marcel,

I have a (kind of) formal request to ask to the Bluez project.

I'm basically trying to use the Bluez API to design a user friendly
device that will have bluetooth functionnality.
Speeking of a user friendly device, i'm thinking of two things i wanna have:
- the end user bluetooth feature should work most of the time, which
means it will have to be robust and not throw errors most of the time.
- When something goes wrong, the end user should only be presented
with error messages he can understand and actually act upon. If the
message is too cryptic, then a generic placeholder would be use instead
of a low level message. One of the first non cryptic messages i think of
would be a "Device unreachable : please check your bluetooth device is
powered on" message :-)

I've done a quick review of hcid an audio service code, and did some
testing too. What i've found is:
- for hcid case: the closed match i found is the
org.audio.bluez.ConnectionAttemptFailed exception. This one seems to be
raised when the L2CAP connection fails. But it is not specific on the
failure cause ( i think what i'm looking for is EHOSTDOWN posix error
code, please correct me if i'm wrong ;-) )
- for Audio service the case is different. Sink object Connect() dbus
call would fail with org.bluez.audio.Error.Failed while the Headset
object Connect() dbus call would fail with
org.bluez.audio.Error.ConnectFailed. Those two are not even consistent :-(
headset.c code looks even a bit hackish, as it tryes to regenerate the
lost EHOSTDOWN error code by hand :

if (dbus_error_has_name(&derr,
"org.bluez.Error.ConnectionAttemptFailed"))
err_connect_failed(device->conn, c->msg,
strerror(EHOSTDOWN));

My point of view is that this common case of error should be clearly
identified and sent up to the application.

What i would like to do is propose a patch that would:
- Define org.bluez.Error.DeviceUnreachable exception for hcid. This
would be fired each time a connect on an l2cap socket would return
EHOSTDOWN.
- Define org.bluez.Error.Audio.DeviceUnreachable for use by the audio
service. This one would be sent by the Headset and Sink objects instead
of the org.bluez.audio.Error.Failed and
org.bluez.audio.Error.ConnectFailed when the l2cap/rfcomm/sco connect()
code returns EHOSTDOWN.

Marcel, would you agree this is the right way to proceed ? Would you be
willing to accept patches that move the code in that direction ?
( I mean : shall i start coding now ? ;-) )

Regards,

Fabien

[-- Attachment #2: fchevalier.vcf --]
[-- Type: text/x-vcard, Size: 253 bytes --]

begin:vcard
fn:Fabien CHEVALIER
n:CHEVALIER;Fabien
org:SILICOM
adr:;;4 rue de Jouanet; RENNES ATALANTE;;35700;FRANCE
email;internet:fchevalier@silicom.fr
title:Software & Studies Engineer
tel;work:+33 (0) 2 99 84 17 17
version:2.1
end:vcard

[-- Attachment #3: Type: text/plain, Size: 314 bytes --]

-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems? Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >> http://get.splunk.com/

[-- Attachment #4: Type: text/plain, Size: 164 bytes --]