From: Andrew Lunn <andrew@lunn.ch>
To: "Allan W. Nielsen" <allan.nielsen@microsemi.com>
Cc: netdev@vger.kernel.org, f.fainelli@gmail.com,
raju.lakkaraju@microsemi.com, cphealy@gmail.com, robh@kernel.org
Subject: Re: [PATCH net-next 5/5] net: phy: Add downshift get/set support in Microsemi PHYs driver
Date: Fri, 4 Nov 2016 14:55:00 +0100 [thread overview]
Message-ID: <20161104135500.GB3600@lunn.ch> (raw)
In-Reply-To: <20161104134234.GC11277@microsemi.com>
On Fri, Nov 04, 2016 at 02:42:34PM +0100, Allan W. Nielsen wrote:
> On 04/11/16 13:27, Andrew Lunn wrote:
> > > + } else if (count) {
> > > + /* Downshift count is either 2,3,4 or 5 */
> > > + count = (((count - 2) << DOWNSHIFT_CNTL_POS) | DOWNSHIFT_EN);
> >
> > Ah, now i see why + 2. But this means it never does what you ask it to
> > do. It would be better to round up < 2 to 2, and leave all the others
> > as is.
> Not sure I understand what you mean...
>
> If the user configure "count == 1", then you want that to be rounded up to
> "count == 2", because the HW does not support a count of 1???
Yes. The other option would be to return ERANGE when 1 is asked
for. The real question is, which is better for the user? Returning
ERANGE and letting the user make a guessing game to figure out what is
valid, or magically turn 1 into 2. I will let you decide which is
best.
> If the user configure count to 6, 7, 8 etc. would you also like to round it down
> to 5?
No. ERANGE. The user has to expect some upper limit, and ERANGE is a
good indication they have reached it. But having a lowered limit of 2
is less obvious.
Andrew
prev parent reply other threads:[~2016-11-04 13:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-04 10:35 [PATCH net-next 0/5] Adding PHY-Tunables and downshift support Allan W. Nielsen
2016-11-04 10:35 ` [PATCH net-next 1/5] ethtool: (uapi) Add ETHTOOL_PHY_GTUNABLE and ETHTOOL_PHY_STUNABLE Allan W. Nielsen
2016-11-04 12:03 ` Andrew Lunn
2016-11-04 12:18 ` Allan W. Nielsen
2016-11-04 12:29 ` Andrew Lunn
2016-11-04 10:35 ` [PATCH net-next 2/5] ethtool: Implements ETHTOOL_PHY_GTUNABLE/ETHTOOL_PHY_STUNABLE Allan W. Nielsen
2016-11-04 12:13 ` Andrew Lunn
2016-11-04 13:31 ` Allan W. Nielsen
2016-11-04 10:35 ` [PATCH net-next 3/5] ethtool: (uapi) Add ETHTOOL_PHY_DOWNSHIFT to PHY tunables Allan W. Nielsen
2016-11-04 10:35 ` [PATCH net-next 4/5] ethtool: Core impl for ETHTOOL_PHY_DOWNSHIFT tunable Allan W. Nielsen
2016-11-04 10:35 ` [PATCH net-next 5/5] net: phy: Add downshift get/set support in Microsemi PHYs driver Allan W. Nielsen
2016-11-04 12:27 ` Andrew Lunn
2016-11-04 13:42 ` Allan W. Nielsen
2016-11-04 13:55 ` Andrew Lunn [this message]
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