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Message-ID: <c18a2b359046a14250cafa5a619dbe53f2872b5a.camel@gmail.com>
Subject: Re: [PATCH  v2 0/4] rpmb subsystem, uapi and virtio-rpmb driver
From:   Bean Huo <huobean@gmail.com>
To:     Alex =?ISO-8859-1?Q?Benn=E9e?= <alex.bennee@linaro.org>
Cc:     linux-kernel@vger.kernel.org, maxim.uvarov@linaro.org,
        joakim.bech@linaro.org, ulf.hansson@linaro.org,
        ilias.apalodimas@linaro.org, arnd@linaro.org,
        ruchika.gupta@linaro.org, tomas.winkler@intel.com,
        yang.huang@intel.com, bing.zhu@intel.com,
        Matti.Moell@opensynergy.com, hmo@opensynergy.com,
        linux-mmc@vger.kernel.org, linux-scsi@vger.kernel.org,
        bvanassche@acm.org
Date:   Wed, 06 Apr 2022 19:19:24 +0200
In-Reply-To: <87ee2ajuky.fsf@linaro.org>
References: <20220405093759.1126835-1-alex.bennee@linaro.org>
         <8b3ce88f65fd11523a4d2daab3c617f7089eb1ce.camel@gmail.com>
         <87r16bk013.fsf@linaro.org>
         <aeb64d1c4bbddfd8463c07a40ab1fc78be0d158d.camel@gmail.com>
         <87ee2ajuky.fsf@linaro.org>
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On Wed, 2022-04-06 at 12:22 +0100, Alex Benn=C3=A9e wrote:
>=20
> Bean Huo <huobean@gmail.com> writes:
>=20
> > On Tue, 2022-04-05 at 16:43 +0100, Alex Benn=C3=A9e wrote:
> > >=20
> > > Bean Huo <huobean@gmail.com> writes:
> > >=20
> > > > Hi Alex,
> > > >=20
> > > > Thanks for this unified RPMB interface, I wanted to verify this
> > > > on
> > > > our
> > > > UFS, it seems you didn't add the UFS access interface in this
> > > > version=20
> > > > from your userspace tools, right?
> > >=20
> > > No I didn't but it should be easy enough to add some function
> > > pointer
> > > redirection everywhere one of the op_* functions calls a vrpmb_*
> > > function. Do you already have a UFS RPMB device driver?
> > >=20
> >=20
> > Hi Alex,
> > Thanks for your feedback.
> >=20
> > We now access UFS RPMB through the RPMB LUN BSG device, RPMB is a
> > well-
> > known LU and we have a userspace tool to access it.
> >=20
> > I see that if we're going to use your interface, "static struct
> > rpmb_ops" should be registered from a lower-level driver, for
> > example
> > in a UFS driver, yes there should be no problem with this
> > registration,
> > but I don't know with the current way Compared, what are the
> > advantages
> > to add a driver. maybe the main advantage is that we will have an
> > unified user space tool for RPMB. right?
>=20
> Pretty much. The main issue for virtio-rpmb is it doesn't really fit
> neatly into the block stack because all it does is the RPMB part so a
> non-block orientate API makes sense.
>=20
> Can you point be to where the UFS driver does it's current RPMB
> stuff?
>=20

It's the SCSI BSG driver, in fact, we don't have a dedicated UFS RPMB
driver in the kernel. RPMB is a well known LU, we are using userspace
tools to issue SCSI commands directly to the UFS RPMB LU via ioctl()
from the BSG device node in the /dev/sg/ folder.

Here is the BSG part of the code in the userspace tools:

        io_hdr_v4.guard =3D 'Q';                                       =20
        io_hdr_v4.protocol =3D BSG_PROTOCOL_SCSI;                      =20
        io_hdr_v4.subprotocol =3D BSG_SUB_PROTOCOL_SCSI_CMD;           =20
        io_hdr_v4.response =3D (__u64)sense_buffer;                    =20
        io_hdr_v4.max_response_len =3D SENSE_BUFF_LEN;                 =20
        io_hdr_v4.request_len =3D cmd_len;                             =20
        io_hdr_v4.request =3D (__u64)cdb;                              =20
                                                                           =
                                              =20
                                                                           =
     =20
        ioctl(fd, SG_IO, &io_hdr_v4))
...


> >=20
> > Kind regards,
> > Bean
>=20
>=20