Plans for hal 0.5.x

Dan Williams dcbw at
Tue Dec 14 07:46:49 PST 2004

On Tue, 2004-12-14 at 17:35 +0300, Andrei Yurkevich wrote:
> Right, at least all PDAs I've seen (and that's been a lot of them) that 
> connect via USB are built this way. They provide some USB device of 
> their own that has got a USB-serial converter bound to that USB 
> interface. However, in the discussion you've mentioned, the idea was to 
> tag that USB device as a PDA. That's ok in case of USB, but when you 
> connect a PDA via serial/IrDA or Bluetooth, you won't have that USB 
> interface device. Instead, you will get a ttyS(n) in case of serial 
> connection, rfcomm(n) for bluetooth and irtty(n) or ircomm(n) for IrDA, 
> all of those being serial interfaces. Moreover, there is a way to 
> distinguish the device connected via these serial interfaces as a PDA or 
> something else, that could be done by HAL itself or a callout. Thus, we 
> could simply tag these serial interfaces with some property like 
> "pda.palm.serial_interface" or "pda.pocket_pc.serial_interface" just to 
> let the interested applications know that these serial ports lead to a 
> PDA device. Finally, some callout/daemon/whatever responsible for 
> establishing a connection with a PDA could do what it needs to when it 
> sees that there is a PDA available behind some serial interface.

Well, since each connection method (USB, serial, bluetooth, etc) is
actually a hardware device itself, why not show the PDA as a _child_ of
that device?  We are working with parent/child relationships as a
fundamental property of HAL already.  Therefore you wouldn't necessarily
need a "pda.palm.serial_interface" property, you could just ask for the
"device.interface" (or something) property of the parent of the PDA
object.  It would seem like having that property on both the PDA _and_
the actual device itself would be redundant.  (however, I can see it
being useful on the PDA so I'm not really objecting to having it there).

The point is, since we can (and if we can't, then we should fix that in
HAL) get that information off the parent of the PDA device, is it really
appropriate to having it on the PDA too?


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