Re: [Bluez-devel] hcid D-Bus patch(Error Messages)

[Claudio Takahasi <cktakahasi@gmail.com>]

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Hi Marcel,

Returning to error messages discussion. Some common errors like EIO(5), and
ENODEV(19) will conflict with Bluetooth failure error codes.
We have three possible solutions:

1. Define different error names. Like:
- org.bluez.HCIError signature: sq(string+uint16)
- org.bluez.DBusError signature: sq(string+uint16)
- org.bluez.SystemError signature: sq(string+uint32)
- org.bluez.ENoMemory(is it necessary? There isn't system code to indicate
it, but
we can consider it as a DBusError because it will be triggered by D-Bus
message
allocation)

2. Use error ranges
Define only one error message name(org.bluez.EFailed), signature: sq
- 0x0000 - 0x00FF Bluetooth error codes
- 0x0100 - 0x01FF D-Bus errors
- 0x0200 - 0x02FF System errors (0x0200 + system error value)
- 0x0300 - 0xFFFF reserved to future error classes

3. Use an extra parameter in the message to indicates the class
Define only one error message name(org.bluez.EFailed), signature: sqq.
But you didn't like this approach.

Please choose one of this alternative to finish this discussion. According
with the last email about errors, you suggested the second approach. But, do
you
agree with this way of handle system errors?

Regards,
Claudio.

On 9/22/05, Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Claudio,
>
> > Regarding the shared code I will analize the shared functions
> > and move to the common directory.
> >
> >
> > The D-Bus error is a message created based on a received message.
> > There are 4 message types:
> > 1. method call message
> > 2. method reply message
> > 3. error message
> > 4. signal
> >
> > First of all you have to understand the difference bus name, path and
> > interface. Read
> > http://dbus.freedesktop.org/doc/dbus-faq.html#id2778454
> > for more information. There is a FAQ with this topic.
>
> this is one of my basic problems with D-Bus and object oriented
> programming in general. They try to abstract and solve everything and
> this is not working. The reality is always different. We now need to
> find a way to make it usable in a sane way.
>
> > After this discussion I would suggest the following structure:
> >
> > >>> Message Error Names:
> > org.bluez.EFailed
> > org.bluez.ENoMemory
> > /* open to more error names */
> >
> > >>>org.bluez.EFailed
> > This error message will have the signature(string+uint16+uint32).
> > Where the first argument is the error description. The second is
> > the error class and the third is the error code.
> > The error class can be system error, D-Bus error or HCI errors.
> > This structure mane possible return to the app clients any kind of
> > error. System error includes socket error, IO, ENODEV... D-Bus error
> > includes no service, no connection, security error and no method
> > found.
> > HCI errors are listed in the bluetooth specification.
>
> We have three different categories of errors. The Bluetooth errors
> defined in the specification. They are the same for the complete HCI.
> Then we have the Unix/Linux error codes (errno) and we will have
> additional codes defined by us. I don't like the idea of splitting the
> errors into classes. This is confusing and not a nice API. We should
> choose a base for the errors and these should be the Bluetooth error
> codes defined in the HCI part specification. So for my point of view an
> error org.bluez.error with string+uint16 is enough. The range 0x00-0xff
> will be used by the Bluetooth errors and we define the rest for specific
> errors that are currently not covered by the specification. This means
> we have to match the Unix/Linux error codes somehow, but I don't see any
> problems with that.
>
> Regards
>
> Marcel
>
>
>
>
>
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