Hi Vinicius, On Tue, 2010-12-28 at 18:48 -0300, Vinicius Costa Gomes wrote: > Hi Brian, > > First of all, sorry for the delay. > [...] > > And taking a closer look at the spec, it was clear to me that only a higher > level profile (above GATT) is able to know that a characteristic needs to be > read by using the "Read Long Characteristic Value" procedure -- which I think is > what brought this discussion, right? or you already have another need for > these procedures? -- Which gives me the impression that this should > be dealt by the profile implementation. Which gives us more time to think about > how to implement this correctly ;-) in case the need arrise. It is true that the "Read Long Characteristic Value" is defined as a distinct GATT procedure from the "Read Characteristic Value" procedure (section 4.8.3 of Vol 3, as opposed to section 4.3.1). However it was purposefully designed such that the two procedures could be overloaded onto a single API such as I have done with the patch(es). (See the Note just above Figure 4.10) I believe that overloading the "Read Characteristic Value" in this way is a valuable extension for a couple of reasons. It simplifies the API (including the DBus API) by not having two APIs that do essentially the same thing. It simplifies the API by not requiring that a client know information ahead of time, such as the length of strings, on a remote server. The fact that this GATT procedure is Optional rather than Mandatory is more a function of common sense rather than a statement of whether it is explicitly needed for a particular profile. For instance a Client may not have the ability to display strings, so there is no point from a specification standpoint of forcing it to read data it is not useful to it. And if a Server with limited resources decides to limit Characteristic Values to 22 octets or less, there is no point in requiring it to respond successfully to a READ_BLOB request. However, as BlueZ will be heavily used, particularly as an LE client, in environments with significant resources (Tablets, Cellphones, Desktops), I think it would be short sighted to require each profile and/or each client app to handle Long and Short Characteristic Values differently, unless there is a compelling technical reason. I personally find the compelling technical reason to be behind overloading the single, simple API. [...] > > Cheers, > -- > Vinicius -- Brian Gix bgix@xxxxxxxxxxxxxx Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
