From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: Problem with multiple i2c multiplexers on the same bus Date: Fri, 31 Oct 2014 22:03:02 +0100 Message-ID: <20141031210301.GA4169@katana> References: Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="qDbXVdCdHGoSgWSk" Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Martin Belanger Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jean Delvare , Guenter Roeck List-Id: linux-i2c@vger.kernel.org --qDbXVdCdHGoSgWSk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, On Mon, Oct 27, 2014 at 11:46:01AM -0700, Martin Belanger wrote: > This is regarding a series of emails between Guenter Roeck and Jean > Delvare titled "Problem with multiple i2c multiplexers on one bus, and > mux bus naming" sent in November 2013. Ref: > http://thread.gmane.org/gmane.linux.drivers.i2c/16980 Please CC those people then, too. That helps getting their attention. I've done this now. > I'm having the same problem with multiple PCA954x multiplexers on the > same bus and there is no way to tell them apart just by looking at the > "name" file. >=20 > There was a suggestion to change the name from "i2c-N-mux (chan_id M)" > to "i2c-N-mux-XX (chan_id M)" or even "i2c-N-mux-i2c-XX (chan_id M)", > where XX is the multiplexer's i2c address. That would solve my > problem, but unfortunately it looks like Guenter never submitted the > patch (or maybe it was rejected?). It just dropped off :( But you guys have my attention now, let's fix this issue for 3.19! I am just reading through the old mails and will think about it. Input is welcome. > I would like to submit a similar change, but I was thinking of adding > a module parameter so that the change is not the default behavior. > The idea is to preserve backward compatibility for applications that > don't require this fix. For example, modprobe i2c-dev > explicit_mux_id=3D1 would use i2c-N-mux-i2c-XX (chan_id M), whereas > modprobe i2c-dev would default to the current behavior: i.e. i2c-N-mux > (chan_id M). I don't like the need to set a module parameter to fix a flaw. I do consider changing the ABI to have better strings in "name". But as said, I need to think about it a little more... Thanks, Wolfram --qDbXVdCdHGoSgWSk Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJUU/kFAAoJEBQN5MwUoCm2WcUQAJWwKOi2RjR/vPoq6n23VWwh FDaJnlygy5yU1q+oKnbnRKHT8QoWqGUkWwRAKK/tKaWGese8tmbS9htQFruJnP4k mopaUOLdChqfowlToA152jtsyw4nPbsmtHUlDo20U8/iaIy0cwXD8JPaNm4KCjru j21XLAbdutN7XtiDx7K0SEQu0LqCcEoUs101DpgryBv7b0671f+DeeQs9q8r+kwA n9L2Tm9QL7vBNtrmS+fHVS8KP/b4ZgnjKml3T7sdvrPIeus1uz/e3BJgqWlORUke 7sNYTK9SD4d0sggITnKWfkZjOvTnT86fonI267DOwOllTLfxXUHYr6Me8mZF7X+h Bf6kNxNbM3u4wuHqQ1mDmRtz9kOk1Cvy0KTFjkHpU+Hkk9jdKNgaGnco1syjVGwb RAPeBHxNcR8etAuP1jgYdscfIuT0Lk3AtGPy5cnfMmFiVmf1LXa1TgcPN8RRyanS PSHgS9cy1o8UuZSmwDGbOiRlGCPDdSj4sCDP46UIpMY4MC2q28n9kRjxSEMZlPwB BpYKk/CBy0ChDamqcezS4yycaCFxcIXQ7Gboj+BXHT4k/F6MyXg+qoxw+ytSRef/ cJsbwrf0KnycTOSuM+K+fsQeZn5VRBJnBm8kCFS/MleMk5RsygWiAM76YpK1smNg Af/W1ZjV0VAQMU/wSvry =+T9m -----END PGP SIGNATURE----- --qDbXVdCdHGoSgWSk--