linux-kernel - Re: [PATCH 2/5] nvme: register ns_id attributes as default sysfs groups

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Message-ID: <20180817070013.GD11170@lst.de>
Date:   Fri, 17 Aug 2018 09:00:13 +0200
From:   "hch@....de" <hch@....de>
To:     Bart Van Assche <Bart.VanAssche@....com>
Cc:     "hare@...e.de" <hare@...e.de>, "axboe@...nel.dk" <axboe@...nel.dk>,
        "hch@....de" <hch@....de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "keith.busch@...el.com" <keith.busch@...el.com>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "hare@...e.com" <hare@...e.com>,
        "sagi@...mberg.me" <sagi@...mberg.me>
Subject: Re: [PATCH 2/5] nvme: register ns_id attributes as default sysfs
        groups

On Tue, Aug 14, 2018 at 03:44:57PM +0000, Bart Van Assche wrote:
> On Tue, 2018-08-14 at 17:39 +0200, Hannes Reinecke wrote:
> > While I have considered having nvme_nvm_register_sysfs() returning a
> > pointer I would then have to remove the 'static' declaration from the
> > nvm_dev_attr_group_12/20.
> > Which I didn't really like, either.
> 
> Hmm ... I don't see why the static declaration would have to be removed from
> nvm_dev_attr_group_12/20 if nvme_nvm_register_sysfs() would return a pointer?
> Am I perhaps missing something?

No, I think that would be the preferable approach IFF patching the global
table of groups would be viable.  I don't think it is, though - we can
have both normal NVMe and LightNVM devices in the same system, so we
can't just patch it over.

So we'll need three different attribut group arrays:

const struct attribute_group *nvme_ns_id_attr_groups[] = {
	&nvme_ns_id_attr_group,
	NULL,
};

const struct attribute_group *lightnvm12_ns_id_attr_groups[] = {
	&nvme_ns_id_attr_group,
	&nvm_dev_attr_group_12,
	NULL,
};

const struct attribute_group *lightnvm20_ns_id_attr_groups[] = {
	&nvme_ns_id_attr_group,
	&nvm_dev_attr_group_20,
	NULL,
};

and a function to select which one to use.