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Fri, 1 Apr 2022 05:05:25 -0400 (EDT) Date: Fri, 1 Apr 2022 11:05:23 +0200 From: Klaus Jensen To: Damien Hedde Subject: Re: [RFC PATCH 0/4] hw/i2c: i2c slave mode support Message-ID: References: <20220331165737.1073520-1-its@irrelevant.dk> <20220331203205.GB29333@minyard.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="j9RmC5DLG7gVmW8w" Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=64.147.123.21; envelope-from=its@irrelevant.dk; helo=wout5-smtp.messagingengine.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Arun Kumar Kashinath Agasar , Corey Minyard , Corey Minyard , Andrew Jeffery , Klaus Jensen , qemu-devel@nongnu.org, Joel Stanley , qemu-arm@nongnu.org, Jeremy Kerr , Padmakar Kalghatgi , Matt Johnston , =?utf-8?Q?C=C3=A9dric?= Le Goater Errors-To: qemu-arm-bounces+alex.bennee=linaro.org@nongnu.org Sender: "Qemu-arm" X-TUID: 0cGvaNcaBSZu --j9RmC5DLG7gVmW8w Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Apr 1 10:58, Damien Hedde wrote: >=20 > On 4/1/22 08:29, Klaus Jensen wrote: > > On Mar 31 15:32, Corey Minyard wrote: > > > On Thu, Mar 31, 2022 at 06:57:33PM +0200, Klaus Jensen wrote: > > > > From: Klaus Jensen > > > >=20 > > > > Hi all, > > > >=20 > > > > This RFC series adds I2C "slave mode" support for the Aspeed I2C > > > > controller as well as the necessary infrastructure in the i2c core = to > > > > support this. > > >=20 > > > I've been wondering when this would happen :). I had put some thought > > > into how this would work, but hadn't come up with anything good. > > >=20 > > > The big disadvantage of this is you are adding an interface that is > > > incompatible with the current masters and slaves. So you are using t= he > > > same I2C bus, but slaves written this way cannot talk to existing > > > masters, and masters written this way cannot talk to existing slave. > > > You could adapt the masters to be able to work either way, and I supp= ose > > > some slaves that could do it could have both an async send and a norm= al > > > send. > >=20 > > Would it make sense to introduce a QOM Interface to differentiate > > between the slave/master types? > >=20 >=20 > Probably. >=20 > I expect a normal slave-only I2C device will be compatible with any master > (having or having not this feature) in real life ? >=20 Yeah, it's just that currently in the i2c core we cannot "suspend" the sending of the ACK. > It would be great if the compatibility between "a I2C slave requiring the > slave-mode from the bus" and the bus could be checked during the device > plug. >=20 Makes sense, I'll see what I can come up with for a v2 :) Thanks! --j9RmC5DLG7gVmW8w Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEUigzqnXi3OaiR2bATeGvMW1PDekFAmJGwFEACgkQTeGvMW1P DekjqQgApMtljS3U+Baho6XQdeB51S2mrxkgKuUgBlpTUwBY57kYQ5GIIZRXGHhC 3x8udxr4DS2NALEpw/NNh0kDpOVc+P11biGK6sRDGtIrGfC9/va0LziWmLtcTNtv TQIoMrz2Xs7+cTU7N1iU9TIDSOGxcYAzlX/buKurJLRFpxrOtX3kdn+r+o6AqZz3 dWy/ts52Ry5iRPt6UYxBFu2iAi7/aITXJeaEkTGwGSnPCrIkW3Ob6EnbBhS1tj0a WA+rS2fqREsAn3ZEn0SEfPsO0gJX3Q6F1idT6lUJ2NwGXnvRu54ShLpecF4qijK9 3UMLPf+9l8LbvpzSAiQeDlKfn4CyMA== =JNW2 -----END PGP SIGNATURE----- --j9RmC5DLG7gVmW8w--