hcid D-Bus patch(Error Messages)

Hi Claudio,

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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

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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.

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After this discussion I would suggest the following structure:

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Message Error Names:

org.bluez.EFailed
org.bluez.ENoMemory
/* open to more error names */

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org.bluez.EFailed

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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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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

Hi Claudio,

Quoted 7 lines

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

I like to go with this approach and a name like org.bluez.Error, because this makes it easy to map the Bluetooth errors. Question is if we should use uint16 or uint32. Maybe the Bluetooth specification extend their error codes to an uint16 instead of an uint8 and then I like to have a free space in this range. Do you think this is a problem?

Regards

Marcel

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it's possible use uint32 without problems.

- 0x00000000 - 0x000000FF Bluetooth error codes (current situation)
- 0x00000100 - 0x0000FFFF Reserved for future Bluetooth error codes extension
- 0x00010000 - 0x0001FFFF D-Bus errors
- 0x00020000 - 0x0003FFFF System errors (0x00020000 + system error value)
- 0x00040000 - 0xFFFFFFFF Reserved to future error classes

In order to make easier discover the error type, I defined the error values range
considering bitwise operations.