On Thu, 7 Jul 2022 13:28:36 +0300 Vladimir Oltean wrote: > Make no mistake, the existing code doesn't disallow reading back the FID > during an ATU Get/Clear Violation operation, and your patch isn't > "allowing" something that wasn't disallowed. > > The documentation for the ATU FID register says that its contents is > ignored before the operation starts, and it contains the returned ATU > entry's FID after the operation completes. > > So the change simply says: don't bother to write the ATU FID register > with zero, it doesn't matter what this contains. This is probably true, > but the patch needs to do what's written on the box. > > Please note that this only even matters at all for switches with > mv88e6xxx_num_databases(chip) > 256, where MV88E6352_G1_ATU_FID is a > dedicated register which this patch avoids writing. For other switches, > the FID is embedded within MV88E6XXX_G1_ATU_CTL or MV88E6XXX_G1_ATU_OP. > So _practically_, for those switches, you are still emitting the > GET_CLR_VIOLATION ATU op with a FID of 0 whether you like it or not, and > this patch introduces a (most likely irrelevant) discrepancy between the > access methods for various switches. > > Please note that this observation is relevant for your future changes to > read back the FID too. As I said here: > https://patchwork.kernel.org/project/netdevbpf/patch/20220524152144.40527-4-schultz.hans+netdev@xxxxxxxxx/#24912482 > you can't just assume that the FID lies within the MV88E6352_G1_ATU_FID > register, just look at the way it is packed within mv88e6xxx_g1_atu_op(). > You'll need to unpack it in the same way. I reckon it'll be useful to render some of this info into the commit message and adjust the subject so marking Changes Requested.
