Hi Johan,
On Fri, Mar 25, 2011 at 12:35 PM, Johan Hedberg <johan.hedberg@xxxxxxxxx> wrote:
> Hi Lizardo,
>
> On Fri, Mar 25, 2011, Anderson Lizardo wrote:
>> > +static u16 get_uuid16(u8 *uuid128)
>> > +{
>> > + u8 *b = bluetooth_base_uuid;
>> > + u32 val;
>> > + int i;
>> > +
>> > + for (i = 4; i < 16; i++) {
>> > + if (b[i] != uuid128[i])
>> > + return 0;
>>
>> Don't you need to check bytes 0 and 1 as well, i.e. only bytes 2 and 3
>> are changed?
>
> The first four bytes can have any value for Bluetooth UUIDs. The purpose
> of this part of the function is to determine whether it's a Bluetooth
> UUID or not (i.e. derived from the Bluetooth base UUID), so the four
> first bytes don't matter.
At least for UUIDs used in attribute types I see this on the spec (page 1835):
"Or, to put it more simply, the 16-bit Attribute UUID replaces the x’s
in the follow-
ing:
0000xxxx-0000-1000-8000-00805F9B34FB"
I.e. , only third and fourth bytes being part of 16-bit UUID.
>> > +static int update_eir(struct hci_dev *hdev)
>> > +{
>> > + struct hci_cp_write_eir cp;
>> > +
>> > + if (!(hdev->features[6] & LMP_EXT_INQ))
>> > + return 0;
>> > +
>> > + if (hdev->ssp_mode == 0)
>> > + return 0;
>> > +
>> > + if (test_bit(HCI_SERVICE_CACHE, &hdev->flags))
>> > + return 0;
>> > +
>> > + memset(&cp, 0, sizeof(cp));
>> > +
>> > + create_eir(hdev, cp.data);
>> > +
>> > + if (memcmp(cp.data, hdev->eir, sizeof(cp.data)) == 0)
>> > + return 0;
>>
>> What about making create_eir() return "int" and check for eir_len and
>> the end? That would avoid the memcmp() here.
>
> I'm not completely sure what you're proposing, but if it's to check for
> matching lengths of cp.data and hdev->eir before doing the memcmp then
> hdev would need a new eir_length member in addition to eir. Could be
> worth it, but it does slightly increase the complexity and since this is
> not a performance critical piece of code (won't be called too often) I'm
> not sure if it's worth it.
Actually I was proposing to get rid of the memcmp(), but now I see it
is necessary to not do HCI_OP_WRITE_EIR if EIR has not changed.
Regards,
--
Anderson Lizardo
Instituto Nokia de Tecnologia - INdT
Manaus - Brazil
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