linux-kernel - Re: [PATCH] virtio_bt: Fix alignment in configuration struct

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Date:   Thu, 11 Aug 2022 10:02:31 -0700
From:   Luiz Augusto von Dentz <luiz.dentz@...il.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Igor Skalkin <igor.skalkin@...nsynergy.com>,
        Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        mgo@...nsynergy.com
Subject: Re: [PATCH] virtio_bt: Fix alignment in configuration struct

Hi Michael,

On Thu, Aug 11, 2022 at 1:00 AM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> On Mon, Aug 08, 2022 at 08:16:11AM -0400, Michael S. Tsirkin wrote:
> > On Mon, Aug 08, 2022 at 02:04:43PM +0200, Igor Skalkin wrote:
> > > On 8/8/22 01:00, Michael S. Tsirkin wrote:
> > >
> > >     On Mon, Aug 08, 2022 at 12:11:52AM +0200, Igor Skalkin wrote:
> > >
> > >         According to specification [1], "For the device-specific configuration
> > >         space, the driver MUST use 8 bit wide accesses for 8 bit wide fields,
> > >         16 bit wide and aligned accesses for 16 bit wide fields and 32 bit wide
> > >         and aligned accesses for 32 and 64 bit wide fields.".
> > >
> > >         Current version of the configuration structure:
> > >
> > >             struct virtio_bt_config {
> > >                 __u8  type;
> > >                 __u16 vendor;
> > >                 __u16 msft_opcode;
> > >             } __attribute__((packed));
> > >
> > >         has both 16bit fields non-aligned.
> > >
> > >         This commit fixes it.
> > >
> > >         [1] https://ddec1-0-en-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=https%3a%2f%2fdocs.oasis%2dopen.org%2fvirtio%2fvirtio%2fv1.1%2fvirtio%2dv1.1.pdf&umid=d1786ace-e8ea-40e8-9665-96c0949174e5&auth=53c7c7de28b92dfd96e93d9dd61a23e634d2fbec-39b15885ceebe9fda9357320aec1ccbac416a470
> > >
> > >         Signed-off-by: Igor Skalkin <Igor.Skalkin@...nsynergy.com>
> > >
> > >     This is all true enough, but the problem is
> > >     1. changing uapi like this can't be done, will break userspace
> > >     2. the driver has more issues and no one seems to want to
> > >        maintain it.
> > >     I posted a patch "Bluetooth: virtio_bt: mark broken" and intend
> > >     to merge it for this release.
> > >
> > > This is very sad. We already use this driver in our projects.
> >
> > Really?  Can you step up to maintain it? Then we can fix the issues
> > and it won't be broken.
>
> Just a reminder that I'm waiting for a response on that.
> I just don't know enough about bluetooth.

Just a heads up that Marcel is on vacation, he did mention that he had
done some work to update virtio_bt thus why I didn't apply any of the
changes yet.

> --
> MST
>


-- 
Luiz Augusto von Dentz