Re: [PATCH net] net: eth: fbnic: Fix addr validation in pcs write

[Andrew Lunn]

On Sat, May 02, 2026 at 05:45:08AM -0400, Mike Marciniszyn wrote:
> On Fri, May 01, 2026 at 02:46:36PM +0100, Simon Horman wrote:
> > On Wed, Apr 29, 2026 at 11:00:49AM -0400, mike.marciniszyn@xxxxxxxxx wrote:
> > > From: "Mike Marciniszyn (Meta)" <mike.marciniszyn@xxxxxxxxx>
> > >
> > > This patch contains a fix for addr validation in fbnic_mdio_write_pcs().
> >
> > Hi Mike,
> >
> > I think this warrants a bit more explanation: Why should addr 2 be
> > accepted? What happens from a user-perspective when it is not?
> >
> 
> The DW IP part has two distinct PCS address ranges cooresponding
> to the C45 PCS registers.
> 
> The shim translates the PCS mmd/addr/regno into specific CSR writes
> to one of two zero-relative addr values into one of those two
> ranges.
> 
> This patch fixes a one off in the test that could allow an invalid
> CSR write if an addr == 2 was called.

Stable runs say:

It must either fix a real bug that bothers people, ...

Can this bug be triggered with the current driver? Are there any
noticeable effects? How would somebody inside Meta know they need this
fix? This should be included in the commit message.

    Andrew