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Date:   Mon, 30 Jul 2018 15:21:07 +0200
From:   Jiri Pirko <jiri@resnulli.us>
To:     Michal Kubecek <mkubecek@suse.cz>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        David Miller <davem@davemloft.net>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Roopa Prabhu <roopa@cumulusnetworks.com>,
        Jakub Kicinski <kubakici@wp.pl>,
        "John W. Linville" <linville@tuxdriver.com>
Subject: Re: [RFC PATCH net-next v2 09/17] ethtool: implement GET_DRVINFO
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Message-ID: <20180730132107.GB10626@nanopsycho>
References: <cover.1532953989.git.mkubecek@suse.cz>
 <4dcd60f25efe368ada4e0c035dc1d7612ab59132.1532953989.git.mkubecek@suse.cz>
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Mon, Jul 30, 2018 at 02:53:27PM CEST, mkubecek@suse.cz wrote:

[...]

>+/* GET_DRVINFO / SET_DRVINFO */
>+
>+enum {
>+	ETHA_DRVINFO_UNSPEC,
>+	ETHA_DRVINFO_DEV,			/* nest - ETHA_DEV_* */
>+	ETHA_DRVINFO_DRIVER,			/* string */
>+	ETHA_DRVINFO_VERSION,			/* string */
>+	ETHA_DRVINFO_FWVERSION,			/* string */
>+	ETHA_DRVINFO_BUSINFO,			/* string */
>+	ETHA_DRVINFO_EROM_VER,			/* string */
>+	ETHA_DRVINFO_N_PRIV_FLAGS,		/* u32 */
>+	ETHA_DRVINFO_N_STATS,			/* u32 */
>+	ETHA_DRVINFO_TESTINFO_LEN,		/* u32 */
>+	ETHA_DRVINFO_EEDUMP_LEN,		/* u32 */
>+	ETHA_DRVINFO_REGDUMP_LEN,		/* u32 */

This is a nice example of why 1:1 ioctl->netlink conversion would be
a big mistake.

I understand that for ioclt, getting lengths of various things is
important. Userspace can prepare buffer for next ioctl which would
actually do dump transfer. However in netlink, this is totally pointless
as the dump goes into userspace in multiple netlink messages.

We need to figure out the netlink uapi from scratch.

[...]