I just tried to introduce another quirk for Realtek Bluetooth controllers when I recognized that the underlying data type (unsigned long) has already run out available bits on system where sizeof(unsigned long) == 4. The number of entries in the (anonymous) quirks enum has already reached 34 in the latest kernels. My first temptation was to simply change the data type to something like __u64, but this is not as easy as it seems. The test_bit() macro used almost everywhere for assigning quirks is guaranteed to be atomic and my platform (ARMv7) seems not to have support for atomic operations on __u64. I mainly see two options: 1. Introducing a 'quirks2' member (bad) This obviously would work, but requires another enum and will (I think) introduce stupid bugs if the wrong quirks member is exercised. 2. Switch to using __64 with non atomic operations About 99% of write accesses to the quirks member happen from probe() or setup() routines which should (I hope) not allow simultaneous access from other contexts. I found 2 exceptions (as of linux-6.12): a. btusb_setup_qca() is called from 'struct hci_dev::open()' (maybe uncritical). b. Two quirks (strict_duplicate_filter, simultaneous_discovery) can be toggled via debugfs. So it looks like using non atomic operations can also introduce trouble if not well reviewed. But as the 'strict_duplicate_filter' and 'simultaneous_discovery' quirks are only used at very few locations, maybe these should be moved to a new member for "atomic quirks", allowing to convert the remaining ones to non atomic. Are there any alternatives? Anything I missed? regards, Christian
