Re: [PATCH net-next v2 5/6] bnxt_en: Skip reading PXP registers during ethtool -d if unsupported

On Wed, 18 Dec 2024 22:57:09 -0800 Michael Chan wrote:

quoted

On Tue, 17 Dec 2024 10:26:19 -0800 Michael Chan wrote:  

quoted

Newer firmware does not allow reading the PXP registers during
ethtool -d, so skip the firmware call in that case.  Userspace
(bnxt.c) always expects the register block to be populated so
zeroes will be returned instead.  

We have both the ability to return the number of registers (regs_len),
and the regs->version. Are you sure you don't want to use either option
to let user space know the regs aren't there?  

The existing bnxt.c in userspace since 2020 always assumes that the
beginning part always contains the PXP register block regardless of
regs->version as long as the register length >= the length of the
register block.  I guess we didn't anticipate that this PXP block
would ever be changed or FW would disallow reading it.

So if you bumped the version the existing userspace wouldn't care but
then you _could_ follow up and update user space to ignore these
registers when version is 1?

It's alright, it's just debug, I got curious recently about how little
use the version field gets. I'm not sure anyone has a good idea on
what to do with it.