Re: [PATCH net-next 0/2] net: dsa: don't unmask port bitmaps

On 10/23/2017 02:26 PM, Vivien Didelot wrote:

Hi Andrew,

Andrew Lunn [off-list ref] writes:

quoted

On Mon, Oct 23, 2017 at 02:17:29PM -0400, Vivien Didelot wrote:

quoted

DSA has several bitmaps to store the type of ports: cpu_port_mask,
dsa_port_mask and enabled_port_mask. But the code is inconsistently
unmasking them.

The legacy code tries to unmask cpu_port_mask and dsa_port_mask but
skips enabled_port_mask.

The new bindings unmasks cpu_port_mask and enabled_port_mask but skips
dsa_port_mask.

In fact there is no need to unmask them because we are in the error
path, and they won't be used after. Instead of fixing the unmasking,
simply remove them.

I'm not looked at the code, travelling and don't have time.

heu, ok.

quoted

What happens if the failure is -PROBE_DEFERRED, and it tried again
later. Will these masks be set back to 0? Or will they retain the old
values? I think there is supposed to be symmetry here, so that we undo
what we did, and so the next time we try again, we start from a good
state.

In case of probe deferral, you get the full probe function to exit with
an error, and that usually involves freeing the recently allocated
dsa_switch instance, and then allocating a new one when probe is
re-entered, so that should not be a problem.

The type of a port is a static information parsed either from device
tree or from platform data. Thus there is no symmetry needed here.

The fact that the unmasking of these bitmaps is currently erroneous also
shows that it is unnecessary.

As much as I would like to see this being symmetrical here, as Vivien
points out, this does not appear to be the case because of missing code,
and it does not seem to solve a particular problem in being symmetrical.
-- 
Florian