linux-kernel - Re: [PATCH v2 08/11] block: sed-opal: ioctl for writing to shadow mbr

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Message-ID: <20180320093604.qge2sdnc5jrud6kg@studium.uni-erlangen.de>
Date:   Tue, 20 Mar 2018 10:36:04 +0100
From:   Jonas Rabenstein <jonas.rabenstein@...dium.uni-erlangen.de>
To:     Christoph Hellwig <hch@....de>
Cc:     Jonas Rabenstein <jonas.rabenstein@...dium.uni-erlangen.de>,
        Scott Bauer <scott.bauer@...el.com>,
        Jonathan Derrick <jonathan.derrick@...el.com>,
        Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 08/11] block: sed-opal: ioctl for writing to shadow mbr

On Mon, Mar 19, 2018 at 08:52:24PM +0100, Christoph Hellwig wrote:
> On Mon, Mar 19, 2018 at 07:36:50PM +0100, Jonas Rabenstein wrote:
> > Allow modification of the shadow mbr. If the shadow mbr is not marked as
> > done, this data will be presented read only as the device content. Only
> > after marking the shadow mbr as done and unlocking a locking range the
> > actual content is accessible.
> 
> I hate doing this as an ioctls.  Can we make this a sysfs binary file
> so that people can use dd or cat to write the shadow mbr?
I already thought about providing a sysfs interface for all that instead
of using ioctls. But as I am pretty new to kernel programming I do not
have all the required insight. Especially, as writing the mbr requires
the sed-opal password I am unsure how a clean sysfs interface to provide
the password together with a simple dd would look like.
Moreover I already have a patch that changes the 'void *data' argument
to setup_opal_dev to a kobject pointer. As far as I know, this is the
first step to get into the sysfs hierarchy. But as I do not have access
to an NVMe drive and have no idea about its implementation, this change
works only for the scsi side.
In other words, if someone could hint me in the right direction, I would
be glad to (re)implement the ioctl interface for sysfs. Moreover, this
would allow to export some additional information like the current state
of the device (is it looke, is sed-opal enabled, whats the current state
of mbr, etc.).

- Jonas