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 F14B7C19F29 for ; Wed, 3 Aug 2022 23:44:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237197AbiHCXoS (ORCPT ); Wed, 3 Aug 2022 19:44:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39816 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237057AbiHCXoR (ORCPT ); Wed, 3 Aug 2022 19:44:17 -0400 Received: from mail-il1-x12b.google.com (mail-il1-x12b.google.com [IPv6:2607:f8b0:4864:20::12b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE4635D0E7 for ; Wed, 3 Aug 2022 16:44:16 -0700 (PDT) Received: by mail-il1-x12b.google.com with SMTP id l9so2642260ilq.1 for ; Wed, 03 Aug 2022 16:44:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=uWHGfg7aX7ICMwSXUYVKFKVf5d3ah58UuK5hBA1Tu+E=; b=ainz+naQb/cSkkTSbrlJkPnd61yZqk6iGas4K5mEyWSY5EZ/NpO7F2OXFEjwqeRqgE KaJXpR+8TV4dJEYWZvu7LR2Wtanl0geTl4Il1cBQX8m8a4G6HM6Jch4PmQI4P3orDNBr zZKPBR2QIpIsuyeyXVGBkPDzGQ9plXt8hgT8s= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=uWHGfg7aX7ICMwSXUYVKFKVf5d3ah58UuK5hBA1Tu+E=; b=jzBrkA+7OpsscN0DNesPzqpYPiI1c3I9m6IMZB+XcD0x9VVDpq7ZLlN1WpEznnGYV/ ofIs796odz4ICitGBYkV+BPggHgs/vlNjjG/rXuLCJKRuZsW+UZ4UJRNZwkR6FKXr6LN gKUaPwNJpOYG/vpCyhV5nL5i5KO17EffvFJmwPtLoVkTCXYKf21SwmTP5RzoIX/DhDN3 JqgvwGDTMxxtaiNXSv6exKt0mD4TTCKK4QJwdmpge3xk1XddL3fvmEHPa5dPWFhsXhNi A2gxzKLa+78LCLnip/aUfsiMbrMhhtgzRJL8CzQFef39i8w4PxmTDOBbP6UVtEoU9RJu R//A== X-Gm-Message-State: AJIora85zlCvVWJLfmsiJ/w4yg+RA5QgUcy2R1fetN/qm81qtamIlHNw iqxJiXWXe3WlrGNvrBLkOTu0FA== X-Google-Smtp-Source: AGRyM1t+7EEqzHBWaMIBsPUh09XoYMcFkX3khxV375085mRxvhaoFmGi/pmZv/uwZ95u6aJszT2p5A== X-Received: by 2002:a05:6e02:1d8e:b0:2dd:47eb:cd1e with SMTP id h14-20020a056e021d8e00b002dd47ebcd1emr11334660ila.221.1659570256210; Wed, 03 Aug 2022 16:44:16 -0700 (PDT) Received: from [192.168.1.128] ([38.15.45.1]) by smtp.gmail.com with ESMTPSA id c14-20020a92cf4e000000b002ddd861f578sm7474021ilr.72.2022.08.03.16.44.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Aug 2022 16:44:15 -0700 (PDT) Subject: Re: [PATCH v3 1/2] drivers: usb/core/urb: Add URB_FREE_COHERENT To: Vincent MAILHOL Cc: Alan Stern , Hongren Zenithal Zheng , Rhett Aultman , linux-usb@vger.kernel.org, linux-can , Oliver Neukum , Marc Kleine-Budde , Greg Kroah-Hartman , Shuah Khan , Shuah Khan References: <20220609204714.2715188-1-rhett.aultman@samsara.com> <20220610213335.3077375-1-rhett.aultman@samsara.com> <20220610213335.3077375-2-rhett.aultman@samsara.com> <143b863d-c86b-6678-44e6-38799391fa36@linuxfoundation.org> <07e82270-cc75-d346-72cf-0a60ffba06dc@linuxfoundation.org> From: Shuah Khan Message-ID: <2a9c8067-2ba8-644f-9362-9f2079e97e11@linuxfoundation.org> Date: Wed, 3 Aug 2022 17:44:15 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org On 8/1/22 12:28 PM, Vincent MAILHOL wrote: > On Tue. 2 Aug. 2022 at 02:48, Shuah Khan wrote: >> On 6/30/22 8:10 PM, Shuah Khan wrote: >>> On 6/27/22 7:35 PM, Alan Stern wrote: >>>> On Mon, Jun 27, 2022 at 04:54:17PM -0600, Shuah Khan wrote: >>>>> On 6/24/22 12:07 PM, Alan Stern wrote: >>>>>> In the future people will want to make other changes to >>>>>> include/linux/usb.h and they will not be aware that those changes will >>>>>> adversely affect usbip, because there is no documentation saying that >>>>>> the values defined in usb.h are part of a user API. That will be a >>>>>> problem, because those changes may be serious and important ones, not >>>>>> just decorative or stylistic as in this case. >>>>>> >>>>> >>>>> How often do these values change based on our past experience with these >>>>> fields? >>>> >>>> I don't know. You could check the git history to find out for certain. >>>> My guess would be every eight or ten years. >>>> >>>>>> I agree with Hongren that values defined in include/linux/ should not be >>>>>> part of a user API. There are two choices: >>>>>> >>>>> >>>>> I agree with this in general. I don't think this is an explicit decision >>>>> to make them part of API. It is a consequence of simply copying the >>>>> transfer_flags. I am with you both on not being able to recognize the >>>>> impact until as this is rather obscure usage hidden away in the packets. >>>>> These defines aren't directly referenced. >>>>> >>>>>> Move the definitions into include/uapi/linux/, or >>>>>> >>>>> >>>>> Wouldn't this be easier way to handle the change? With this option >>>>> the uapi will be well documented. >>>>> >>>>>> Add code to translate the values between the numbers used in >>>>>> userspace and the numbers used in the kernel. (This is what >>>>>> was done for urb->transfer_flags in devio.c:proc_do_submiturb() >>>>>> near line 1862.) >>>>>> >>>>> >>>>> I looked at the code and looks simple enough. I am okay going this route >>>>> if we see issues with the option 1. >>>> >>>> It's up to you; either approach is okay with me. However, I do think >>>> that the second option is a little better; I don't see any good reason >>>> why the kernel should be forced to use the same numeric values for these >>>> flags forever. Especially since the only user program that needs to >>>> know them is usbip, which is fairly closely tied to the kernel; if there >>>> were more programs using those values then they would constitute a good >>>> reason for choosing the first option. >>>> >>> >>> Thank you Alan and Hongren for your help with this problem. Since there >>> are no changes to the flags for the time being, I am comfortable going >>> with the second option. >>> >>> I will send a patch soon. >>> >> >> Patch is almost ready to be sent out. Changes aren't bad at all. Hoping to >> get this done sooner - summer vacations didn't cooperate. >> >> Just an update that I haven't forgotten and it will taken care of. >> thanks, > > Thanks for keeping this under your radar. I also have on my TODO list > to send a new version of my patch to add the `URB_FREE_COHERENT' flag > but this time adding an `allocated_length' field to struct urb. I will > wait for your patch to go first. By the way, I will be out for summer > holiday for the next couple of weeks so I wasn't planning to submit > anything soon regardless. > Sounds good. I now have the patch ready to be sent out. I will wait for the merge window to close before I send it out. thanks, -- Shuah