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Tsirkin" To: Igor Skalkin Cc: Jason Wang , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , linux-bluetooth@vger.kernel.org, mgo@opensynergy.com Subject: Re: [PATCH] virtio_bt: Fix alignment in configuration struct Message-ID: <20221007090223-mutt-send-email-mst@kernel.org> References: <20220807221152.38948-1-Igor.Skalkin@opensynergy.com> <20220807185846-mutt-send-email-mst@kernel.org> <02222fcb-eaba-617a-c51c-f939678e3d74@opensynergy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <02222fcb-eaba-617a-c51c-f939678e3d74@opensynergy.com> Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org 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 > > 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. Ping. If we still have no maintainer I'm marking it broken, users should at least be warned. > Our virtio bluetooth device has two backends - HCI_USER socket backend for one > platform and uart backend for the other, and works well (after applying your > "[PATCH] Bluetooth: virtio_bt: fix device remove") patch, so this "device > removal" problem can probably be considered solved . > We could help with the rest of the problems you listed that can be solved > (specification, QEMU support). > And the only problem that is difficult to solve (because of the need to change > UAPI header files) is just this one with unaligned configuration fields. > At the moment, it does not reproduce, because without VIRTIO_BT_F_VND_HCI > (Indicates vendor command support) feature negotiated, the driver does not > read the non-aligned configuration fields. > > So, what would you advise us to do? Continuing to use the "marked broken" > driver, start writing a specification for a new from scratch, better one? > Or is there any way to bring this one back to life? > > > > --- > include/uapi/linux/virtio_bt.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/uapi/linux/virtio_bt.h b/include/uapi/linux/virtio_bt.h > index a7bd48daa9a9..adc03709cc4f 100644 > --- a/include/uapi/linux/virtio_bt.h > +++ b/include/uapi/linux/virtio_bt.h > @@ -23,9 +23,9 @@ enum virtio_bt_config_vendor { > }; > > struct virtio_bt_config { > - __u8 type; > __u16 vendor; > __u16 msft_opcode; > + __u8 type; > } __attribute__((packed)); > > #endif /* _UAPI_LINUX_VIRTIO_BT_H */ > -- > 2.34.1 > > -- > > Best regards, > > Igor Skalkin > Software Engineer > > OpenSynergy GmbH > Rotherstr. 20, 10245 Berlin > > igor.skalkin@opensynergy.com > www.opensynergy.com > > registered: Amtsgericht Charlottenburg, HRB 108616B > General Management: Rolf Morich, Stefaan Sonck Thiebaut > > > Please mind our privacy notice pursuant to Art. 13 GDPR. // Unsere Hinweise zum > Datenschutz gem. Art. 13 DSGVO finden Sie hier.