From: Boris Brezillon <boris.brezillon@collabora.com>
To: Vitor Soares <Vitor.Soares@synopsys.com>
Cc: Jose Abreu <Jose.Abreu@synopsys.com>,
Joao Pinto <Joao.Pinto@synopsys.com>,
"arnd@arndb.de" <arnd@arndb.de>,
"corbet@lwn.net" <corbet@lwn.net>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"wsa@the-dreams.de" <wsa@the-dreams.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"broonie@kernel.org" <broonie@kernel.org>,
"linux-i3c@lists.infradead.org" <linux-i3c@lists.infradead.org>,
"bbrezillon@kernel.org" <bbrezillon@kernel.org>
Subject: Re: [PATCH v3 4/5] i3c: add i3cdev module to expose i3c dev in /dev
Date: Mon, 24 Feb 2020 12:22:06 +0100 [thread overview]
Message-ID: <20200224122206.10984b3f@collabora.com> (raw)
In-Reply-To: <CH2PR12MB42163351853CCC029D28164BAEEC0@CH2PR12MB4216.namprd12.prod.outlook.com>
On Mon, 24 Feb 2020 11:04:50 +0000
Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> Hi Boris,
>
> From: Boris Brezillon <boris.brezillon@collabora.com>
> Date: Fri, Feb 21, 2020 at 22:32:16
>
> > On Wed, 19 Feb 2020 01:20:42 +0100
> > Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> >
> > > +static int i3cdev_detach(struct device *dev, void *dummy)
> > > +{
> > > + struct i3cdev_data *i3cdev;
> > > + struct i3c_device *i3c;
> > > +
> > > + if (dev->type == &i3c_masterdev_type)
> > > + return 0;
> > > +
> > > + i3c = dev_to_i3cdev(dev);
> > > +
> > > + i3cdev = i3cdev_get_drvdata(i3c);
> > > + if (!i3cdev)
> > > + return 0;
> > > +
> > > + /* Prevent transfers while cdev removal */
> > > + mutex_lock(&i3cdev->xfer_lock);
> > > + cdev_del(&i3cdev->cdev);
> >
> > When cdev_del() returns there might be opened FDs pointing to your
> > i3cdev [1] ...
>
> Yes, I know. I protected the driver part but I missed the
> file->private_data.
Not sure what you mean by protection, but if you meant locking, then
it's not enough: you need to refcnt the struct if you want to prevent
use-after-free situations.
BTW, I had a closer look at the usbdev implementation, and maybe you
should base yours on usb instead of i2c. They seem to register a cdev at
module init time, and add a dev_t per device at device registration
time. Not sure how they handle the userspace-driver vs kernel-driver
concurrency, but maybe returning EACCES (or EBUSY) instead of
detaching/attaching the i3cdev everytime a device is bound/unbound
would be simpler.
Also, I think Arnd was right, it'd be simpler if i3cdev support was
integrated to the core (still left as a option so it can be disabled,
but with a dedicated i3cdev field in i3c_device instead hijacking the
driver private field).
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next prev parent reply other threads:[~2020-02-24 11:22 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 0:20 [PATCH v3 0/5] Introduce i3c device userspace interface Vitor Soares
2020-02-19 0:20 ` [PATCH v3 1/5] i3c: master: export i3c_masterdev_type Vitor Soares
2020-02-19 0:20 ` [PATCH v3 2/5] i3c: master: export i3c_bus_type symbol Vitor Soares
2020-02-19 0:20 ` [PATCH v3 3/5] i3c: master: add i3c_for_each_dev helper Vitor Soares
2020-02-19 7:35 ` Greg KH
2020-02-21 11:47 ` Vitor Soares
2020-02-21 11:52 ` Greg KH
2020-02-21 12:59 ` Boris Brezillon
2020-02-21 16:44 ` Boris Brezillon
2020-02-21 16:45 ` Boris Brezillon
2020-02-21 17:19 ` Vitor Soares
2020-02-22 8:38 ` Boris Brezillon
2020-02-19 0:20 ` [PATCH v3 4/5] i3c: add i3cdev module to expose i3c dev in /dev Vitor Soares
2020-02-19 7:37 ` Greg KH
2020-02-19 8:45 ` Vitor Soares
2020-02-19 7:39 ` Greg KH
2020-02-21 11:50 ` Vitor Soares
2020-02-19 8:42 ` Greg KH
2020-02-21 22:32 ` Boris Brezillon
2020-02-24 11:04 ` Vitor Soares
2020-02-24 11:22 ` Boris Brezillon [this message]
2020-02-19 0:20 ` [PATCH v3 5/5] add i3cdev documentation Vitor Soares
2020-02-19 0:46 ` Vitor Soares
2020-02-19 4:34 ` Randy Dunlap
2020-02-21 10:31 ` Vitor Soares
2020-02-21 15:36 ` Randy Dunlap
2020-02-19 0:39 ` [PATCH v3 0/5] Introduce i3c device userspace interface Vitor Soares
2020-02-19 8:16 ` Boris Brezillon
2020-02-21 17:08 ` Vitor Soares
2020-02-21 17:41 ` Boris Brezillon
2020-02-24 10:53 ` Vitor Soares
2020-02-24 11:24 ` Boris Brezillon
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