From: Johannes Berg <johannes@sipsolutions.net>
To: Michal Kubecek <mkubecek@suse.cz>, netdev@vger.kernel.org
Cc: Jiri Pirko <jiri@resnulli.us>, David Miller <davem@davemloft.net>,
Jakub Kicinski <jakub.kicinski@netronome.com>,
Andrew Lunn <andrew@lunn.ch>,
Florian Fainelli <f.fainelli@gmail.com>,
John Linville <linville@tuxdriver.com>,
Stephen Hemminger <stephen@networkplumber.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next v6 06/15] ethtool: netlink bitset handling
Date: Thu, 04 Jul 2019 15:10:11 +0200 [thread overview]
Message-ID: <a6fbee05df0efd2528a06922bcb514d321b1a8bc.camel@sipsolutions.net> (raw)
In-Reply-To: <20190704125315.GT20101@unicorn.suse.cz>
On Thu, 2019-07-04 at 14:53 +0200, Michal Kubecek wrote:
>
> > value: 0b00000000'000000xx'xxxxxxxx'xxxxxxxx
> > mask: 0b00000000'00000011'11111111'11111111
>
> One scenario that I can see from the top of my head would be user
> running
>
> ethtool -s <dev> advertise 0x...
The "0x..." here would be the *value* in the NLA_BITFIELD32 parlance,
right?
What would the "selector" be? I assume the selector would be "whatever
ethtool knows about"?
> with hex value representing some subset of link modes. Now if ethtool
> version is behind kernel and recognizes fewer link modes than kernel
> but in a way that the number rounded up to bytes or words would be the
> same, kernel has no way to recognize of those zero bits on top of the
> mask are zero on purpose or just because userspace doesn't know about
> them. In general, I believe the absence of bit length information is
> something protocols would have to work around sometimes.
>
> The submitted implementation doesn't have this problem as it can tell
> kernel "this is a list" (i.e. I'm not sending a value/mask pair, I want
> exactly these bits to be set).
OK, here I guess I see what you mean. You're saying if ethtool were to
send a value/mask of "0..0100/0..0111" you wouldn't know what to do with
BIT(4) as long as the kernel knows about that bit?
I guess the difference now is depending on the operation. NLA_BITFIELD32
is sort of built on the assumption of having a "toggle" operation. If
you want to have a "set to" operation, then you don't really need the
selector/mask at all, just the value.
johannes
next prev parent reply other threads:[~2019-07-04 13:10 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-02 11:49 [PATCH net-next v6 00/15] ethtool netlink interface, part 1 Michal Kubecek
2019-07-02 11:49 ` [PATCH net-next v6 01/15] rtnetlink: provide permanent hardware address in RTM_NEWLINK Michal Kubecek
2019-07-02 11:57 ` Jiri Pirko
2019-07-02 14:55 ` Stephen Hemminger
2019-07-02 16:35 ` Michal Kubecek
2019-07-02 11:49 ` [PATCH net-next v6 02/15] netlink: rename nl80211_validate_nested() to nla_validate_nested() Michal Kubecek
2019-07-02 12:03 ` Jiri Pirko
2019-07-02 12:15 ` Johannes Berg
2019-07-02 12:15 ` Johannes Berg
2019-07-02 11:49 ` [PATCH net-next v6 03/15] ethtool: move to its own directory Michal Kubecek
2019-07-02 11:49 ` [PATCH net-next v6 04/15] ethtool: introduce ethtool netlink interface Michal Kubecek
2019-07-02 12:25 ` Jiri Pirko
2019-07-02 14:52 ` Michal Kubecek
2019-07-03 8:41 ` Jiri Pirko
2019-07-08 17:27 ` Michal Kubecek
2019-07-08 18:12 ` Johannes Berg
2019-07-08 19:26 ` Jiri Pirko
2019-07-08 19:28 ` Jiri Pirko
2019-07-08 20:22 ` Michal Kubecek
2019-07-09 13:42 ` Jiri Pirko
2019-07-10 12:12 ` Michal Kubecek
2019-07-03 1:29 ` Jakub Kicinski
2019-07-03 6:35 ` Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 05/15] ethtool: helper functions for " Michal Kubecek
2019-07-02 13:05 ` Jiri Pirko
2019-07-02 16:34 ` Michal Kubecek
2019-07-03 1:28 ` Jakub Kicinski
2019-07-03 10:04 ` Jiri Pirko
2019-07-03 11:13 ` Michal Kubecek
2019-07-08 12:22 ` Michal Kubecek
2019-07-08 14:40 ` Jiri Pirko
2019-07-03 1:37 ` Jakub Kicinski
2019-07-03 7:23 ` Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 06/15] ethtool: netlink bitset handling Michal Kubecek
2019-07-03 11:49 ` Jiri Pirko
2019-07-03 13:44 ` Johannes Berg
2019-07-03 14:37 ` Jiri Pirko
2019-07-04 12:07 ` Johannes Berg
2019-07-03 18:18 ` Michal Kubecek
2019-07-04 8:04 ` Jiri Pirko
2019-07-04 11:52 ` Michal Kubecek
2019-07-04 12:03 ` Johannes Berg
2019-07-04 12:17 ` Michal Kubecek
2019-07-04 12:21 ` Johannes Berg
2019-07-04 12:53 ` Michal Kubecek
2019-07-04 13:10 ` Johannes Berg [this message]
2019-07-04 14:31 ` Andrew Lunn
2019-07-09 14:18 ` Jiri Pirko
2019-07-10 12:38 ` Michal Kubecek
2019-07-10 12:59 ` Jiri Pirko
2019-07-10 14:37 ` Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 07/15] ethtool: support for netlink notifications Michal Kubecek
2019-07-03 13:33 ` Jiri Pirko
2019-07-03 14:16 ` Michal Kubecek
2019-07-04 8:06 ` Jiri Pirko
2019-07-03 13:39 ` Johannes Berg
2019-07-03 14:18 ` Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 08/15] ethtool: move string arrays into common file Michal Kubecek
2019-07-03 13:44 ` Jiri Pirko
2019-07-03 14:37 ` Michal Kubecek
2019-07-04 8:09 ` Jiri Pirko
2019-07-02 11:50 ` [PATCH net-next v6 09/15] ethtool: generic handlers for GET requests Michal Kubecek
2019-07-03 14:25 ` Jiri Pirko
2019-07-03 17:53 ` Michal Kubecek
2019-07-04 8:45 ` Jiri Pirko
2019-07-04 8:49 ` Jiri Pirko
2019-07-04 9:28 ` Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 10/15] ethtool: provide string sets with STRSET_GET request Michal Kubecek
2019-07-04 8:17 ` Jiri Pirko
2019-07-02 11:50 ` [PATCH net-next v6 11/15] ethtool: provide link mode names as a string set Michal Kubecek
2019-07-03 2:04 ` Jakub Kicinski
2019-07-03 2:11 ` Jakub Kicinski
2019-07-03 7:38 ` Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 12/15] ethtool: provide link settings and link modes in SETTINGS_GET request Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 13/15] ethtool: add standard notification handler Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 14/15] ethtool: set link settings and link modes with SETTINGS_SET request Michal Kubecek
2019-07-02 11:50 ` [PATCH net-next v6 15/15] ethtool: provide link state in SETTINGS_GET request Michal Kubecek
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