From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DED0C433F5 for ; Wed, 19 Jan 2022 08:28:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352461AbiASI2K (ORCPT ); Wed, 19 Jan 2022 03:28:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46492 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350447AbiASI2H (ORCPT ); Wed, 19 Jan 2022 03:28:07 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DAB62C061574 for ; Wed, 19 Jan 2022 00:28:06 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 77E3E61447 for ; Wed, 19 Jan 2022 08:28:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 45715C004E1; Wed, 19 Jan 2022 08:28:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1642580885; bh=vg0ymns1lhOX8VazK7xuSFllvE018HiEtIFtrwVk3pI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ajqYcA4mujEDsMt2WWy+ZZ8qNa60BZSmTVw/35HlqNNInT0qPcCYTapUFWM+P2kNl pwgTX64KAbo4sBZXkVpoymwu/WLRHEAnVAl8R0ARd+FEp00uhy4BjVvZc1/X31HWDj /UOlsfycgGLzE7e0ikLSudcXPViJxXYz1ySQzyiU= Date: Wed, 19 Jan 2022 09:28:03 +0100 From: Greg KH To: Benson Leung Cc: Rajaram Regupathy , linux-usb@vger.kernel.org, heikki.krogerus@linux.intel.com, Prashant Malani , jthies@google.com, saranya.gopal@intel.com Subject: Re: [ANNOUNCE] libtypec_0.1/lstypec_0.1 is released Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, Jan 18, 2022 at 11:16:28AM -0800, Benson Leung wrote: > Hi Greg, > > On Tue, Jan 18, 2022 at 07:33:39PM +0100, Greg KH wrote: > > On Tue, Jan 18, 2022 at 10:01:02PM +0530, Rajaram Regupathy wrote: > > > > Again, why does this have to be a library? > > > > > > > The aim of having a library is to abstract application(s) from OS, > > > platform, PD Controller or Embedded Controller protocols ambiguities > > > and provide common methods. The methods will be similar/closer to UCSI > > > standard. > > > > What methods are needed by an operating system that your library is > > going to provide? How will it be done in a unified way that the current > > user/kernel api isn't providing already today? > > > > A unified libtypec would be useful because the USB Type-C and USB PD > specifications are evolving, and continue to change. Spec changes affect the > decoding of the objects that are exposed by the connector class (the existing > API), and we are at a point where if we left it as-is, you'd have multiple > userspace implementations that would have to independently be updated and > fixed every time there's a new USB PD spec revision or version update. > > Just as a concrete example, Jameson (jthies@google.com), who works on my team, > recently put together a little helper utility to decode the typec connector > class in order to print it to our feedback report collector. This was all > done before libtypec: > > https://chromium.googlesource.com/chromiumos/platform2/+/749621a6288cc5e80b31a9e6050437a419209fb9/debugd/src/helpers/typec_connector_class_helper.cc > > A problem we ran into almost immediately was that the utility was based on > the most recent USB PD specification documents (USB PD R2.0 and USB PD R3.1), > and had definitions on how to decode PD 2.0 and PD 3.1 objects that it would > read from the typec connector class, however, it was missing definitions for > USB PD R3.0 (a spec revision which is not obvious how to find in USB-IF's > document archive). > > So, we added it: https://chromium.googlesource.com/chromiumos/platform2/+/eb1efefc187feab1182a7680f42fcec6bb14c618 > > Now, every other hypothetical type-c connector class user application or daemon > could potentially make this mistake, and would have to duplicate the work > to fix it. > > If we had libtypec, it would be the unified place to make such a change, and > we'd reduce the burden of new typec apps from having to do all this decode > in the future. Ok, that's fine, but please work to create a library that can handle such changes in non-breaking ways. The first version of this library does not look like it would do that at all as it is exporting way too many things in a "public" interface. thanks, greg k-h