Subject: Re: [PATCH net-next] net: sfp: add debugfs support

From: Ido Schimmel <[email-masked]>
Date: Tue, 24 Nov 2020 10:41:51 +0200

On Tue, Nov 24, 2020 at 01:14:31AM +0100, Andrew Lunn wrote:
> On Mon, Nov 23, 2020 at 10:06:16PM +0000, Russell King wrote:
> > Add debugfs support to SFP so that the internal state of the SFP state
> > machines and hardware signal state can be viewed from userspace, rather
> > than having to compile a debug kernel to view state state transitions
> > in the kernel log.  The 'state' output looks like:
> > 
> > Module state: empty
> > Module probe attempts: 0 0
> > Device state: up
> > Main state: down
> > Fault recovery remaining retries: 5
> > PHY probe remaining retries: 12
> > moddef0: 0
> > rx_los: 1
> > tx_fault: 1
> > tx_disable: 1
> > 
> > Signed-off-by: Russell King <[email-masked]>
> 
> Hi Russell
> 
> This looks useful. I always seem to end up recompiling the kernel,
> which as you said, this should avoid.

FWIW, another option is to use drgn [1]. Especially when the state is
queried from the kernel and not hardware. We are using that in mlxsw
[2][3].

[1] https://github.com/osandov/drgn
[2] https://github.com/Mellanox/mlxsw/blob/master/Debugging/hdroom_dump.txt
[3] https://github.com/Mellanox/mlxsw/blob/master/Debugging/hdroom_dump.py