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    SubjectRe: [PATCH 2/2] e1000e: Make WOL info in ethtool consistent with device wake up ability
    Hi Michal,
    Thanks for reviewing,
    and sorry for late reply.
    On Thu, May 21, 2020 at 09:23:42PM +0200, Michal Kubecek wrote:
    > On Fri, May 22, 2020 at 01:59:13AM +0800, Chen Yu wrote:
    > > Currently the ethtool shows that WOL(Wake On Lan) is enabled
    > > even if the device wakeup ability has been disabled via sysfs:
    > > cat /sys/devices/pci0000:00/0000:00:1f.6/power/wakeup
    > > disabled
    > >
    > > ethtool eno1
    > > ...
    > > Wake-on: g
    > >
    > > Fix this in ethtool to check if the user has explicitly disabled the
    > > wake up ability for this device.
    >
    > Wouldn't this lead to rather unexpected and inconsistent behaviour when
    > the wakeup is disabled? As you don't touch the set_wol handler, I assume
    > it will still allow setting enabled modes as usual so that you get e.g.
    >
    > ethtool -s eth0 wol g # no error or warning, returns 0
    > ethtool eth0 # reports no modes enabled
    >
    > The first command would set the enabled wol modes but that would be
    > hidden from user and even the netlink notification would claim something
    > different. Another exampe (with kernel and ethtool >= 5.6):
    >
    > ethtool -s eth0 wol g
    > ethtool -s eth0 wol +m
    >
    > resulting in "mg" if device wakeup is enabled but "m" when it's disabled
    > (but the latter would be hidden from user and only revealed when you
    > enable the device wakeup).
    >
    I've tested ethtool v5.6 on top of kernel v5.7-rc6, it looks like
    the scenario you described will not happen as it will not allow
    the user to enable the wol options with device wakeup disabled,
    not sure if I missed something:

    /sys/devices/pci0000:00/0000:00:1f.6/power# echo disabled > wakeup

    ethtool -s eno1 wol g
    netlink error: cannot enable unsupported WoL mode (offset 36)
    netlink error: Invalid argument

    I've not digged into the code too much, but according to
    ethhl_set_wol(), it will first get the current wol options
    via dev->ethtool_ops->get_wol(), and both the wolopts and
    wol.supported are 0 when device wake up are disabled. Then
    ethnl_update_bitset32 might manipulate on wolopts and
    make it non-zero each is controdict with the precondition that
    no opts should be enabled due to 0 wol.supported.
    > This is a general problem discussed recently for EEE and pause
    > autonegotiation: if setting A can be effectively used only when B is
    > enabled, should we hide actual setting of A from userspace when B is
    > disabled or even reset the value of A whenever B gets toggled or rather
    > allow setting A and B independently? AFAICS the consensus seemed to be
    > that A should be allowed to be set and queried independently of the
    > value of B.

    But then there would be an inconsistence between A and B. I was thinking
    if there's a way to align them in kernel space and maintain the difference in user space?

    Thanks,
    Chenyu
    >
    > Michal
    >
    > > Fixes: 6ff68026f475 ("e1000e: Use device_set_wakeup_enable")
    > > Reported-by: Len Brown <len.brown@intel.com>
    > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
    > > Cc: <Stable@vger.kernel.org>
    > > Signed-off-by: Chen Yu <yu.c.chen@intel.com>
    > > ---
    > > drivers/net/ethernet/intel/e1000e/ethtool.c | 2 +-
    > > 1 file changed, 1 insertion(+), 1 deletion(-)
    > >
    > > diff --git a/drivers/net/ethernet/intel/e1000e/ethtool.c b/drivers/net/ethernet/intel/e1000e/ethtool.c
    > > index 1d47e2503072..0cccd823ff24 100644
    > > --- a/drivers/net/ethernet/intel/e1000e/ethtool.c
    > > +++ b/drivers/net/ethernet/intel/e1000e/ethtool.c
    > > @@ -1891,7 +1891,7 @@ static void e1000_get_wol(struct net_device *netdev,
    > > wol->wolopts = 0;
    > >
    > > if (!(adapter->flags & FLAG_HAS_WOL) ||
    > > - !device_can_wakeup(&adapter->pdev->dev))
    > > + !device_may_wakeup(&adapter->pdev->dev))
    > > return;
    > >
    > > wol->supported = WAKE_UCAST | WAKE_MCAST |
    > > --
    > > 2.17.1
    > >

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