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 C3FB9C88CB4 for ; Mon, 12 Jun 2023 16:08:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232894AbjFLQID (ORCPT ); Mon, 12 Jun 2023 12:08:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231779AbjFLQH6 (ORCPT ); Mon, 12 Jun 2023 12:07:58 -0400 Received: from smtpcmd13147.aruba.it (smtpcmd13147.aruba.it [62.149.156.147]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8670A130 for ; Mon, 12 Jun 2023 09:07:55 -0700 (PDT) Received: from [192.168.1.56] ([79.0.204.227]) by Aruba Outgoing Smtp with ESMTPSA id 8k5AqyVHYzrnG8k5AqvqoC; Mon, 12 Jun 2023 18:07:53 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=aruba.it; s=a1; t=1686586073; bh=C9lVHEipiO2rrCzzjQikvmaiVgb86Ugo7xwo8BBwLEI=; h=Date:MIME-Version:Subject:To:From:Content-Type; b=dI9xtEsx7I/q9LipVhMy6AeyMKy9t2iBAgqNv2sUxFgbpW/3AYk2vQtS7lnzubwY5 h12p3zCn5000JWTMUIqviOv29aWdAjO/exAecYuUEOAaDA7YrzAKw9jOLoVWwEADfX G5jaFMwReCVppn7n+re2gsD/axYNJDFSZtw660gSlxOqgHZxLGvSyEXvRBN7lbAZii wWFSrbjDruGTttqbTZeqmiPjNZVqZRrNlqWJglXhgB6y5fiRULESCkY/buv1X0nI62 akdc2mrMa1F2ZMZXZFq20U4SRmtrrod5aPXAjuS7iySkSzd9fUNqs2UqdLPvuMt8ja 9c+SexGH/zszA== Message-ID: <5aff32cf-74ea-b632-9d4d-a01ca0d31821@enneenne.com> Date: Mon, 12 Jun 2023 18:07:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [RFC PATCH] pps: Increase PPS_MAX_SOURCES value. Content-Language: en-US To: Charlie Johnston Cc: linux-kernel@vger.kernel.org, brenda.streiff@ni.com References: <20230605203147.694716-1-charlie.johnston@ni.com> <70ce864c-ca13-4fc4-fcb5-9b7f91579a90@enneenne.com> <38f38f66-0fd5-4e6c-4839-8272cef77046@ni.com> From: Rodolfo Giometti In-Reply-To: <38f38f66-0fd5-4e6c-4839-8272cef77046@ni.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CMAE-Envelope: MS4xfNHoWjjsDpVkUmd/TjHXIrjmHcri4vNat0TGanoRsRoOMzkR5nrRHbQGIHBudJwgES0nT2Rnxgqcr2dPao7ZocMFC3jp7JzSO/wJNwtMI0emnN1GUHC6 Vquc8MCzBQ9WoP5vhtdyDxB2ii3AuWzu6VhRV2Yy6lGORcGejJsHYuf54YhTeEaYzgvQt19webGzA7F+5XhBt4hYTyx591gwvJQP+408o/Hva2KBVGSjH4Tu 4U6l0H58wBhejizaqu/Fxc2DAKFpjOpAFplm2anCLGk= Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/06/23 23:00, Charlie Johnston wrote: > On 6/9/23 02:30, Rodolfo Giometti wrote: >> On 08/06/23 00:07, Charlie Johnston wrote: >>> On 6/7/23 02:33, Rodolfo Giometti wrote: >>>> On 05/06/23 22:31, Charlie Johnston wrote: >>>>> For consistency with what ptp uses for minors, this >>>>> change sets PPS_MAX_SOURCES to MINORMASK + 1. >>>>> >>>>> The PPS_MAX_SOURCES value is currently set to 16. In >>>>> some cases this was not sufficient for a system. For >>>>> example, a system with multiple (4+) PCIe cards each >>>>> with 4 PTP-capable ethernet interfaces could run out >>>>> of the available PPS major:minors if each interface >>>>> registers a PPS source. >>>>> >>>>> Signed-off-by: Charlie Johnston >>>>> --- >>>>>    include/uapi/linux/pps.h | 2 +- >>>>>    1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/include/uapi/linux/pps.h b/include/uapi/linux/pps.h >>>>> index 009ebcd8ced5..85f472330da8 100644 >>>>> --- a/include/uapi/linux/pps.h >>>>> +++ b/include/uapi/linux/pps.h >>>>> @@ -26,7 +26,7 @@ >>>>>    #include >>>>>      #define PPS_VERSION        "5.3.6" >>>>> -#define PPS_MAX_SOURCES        16        /* should be enough... */ >>>>> +#define PPS_MAX_SOURCES        (MINORMASK + 1) >>>>>      /* Implementation note: the logical states ``assert'' and ``clear'' >>>>>     * are implemented in terms of the chip register, i.e. ``assert'' >>>> >>>> I have just one question: are you sure that it's safe to call idr_alloc(..., 0, (MINORMASK + 1), ...)? >>>> >>>> Ciao, >>>> >>>> Rodolfo >>>> >>> >>> Thanks for taking a look! >>> >>> My understanding is that idr_alloc(..., start, end, ...) can take any end value up to INT_MAX. It also handles any values <= 0 by treating them as equal to INT_MAX + 1 since the end value is non-inclusive. I can't think of any reason using MINORMASK + 1 here would be an issue since it's much less than the maximum value idr_alloc() allows. >>> >>> A number of drivers (e.g. ptp) just explicitly use a start and end value of 0, but I don't think that change would fit here. >> >> I see and maybe I should replace the usage of idr_*() with ida_*() as PTP does... >> >> However the right-thing(TM) to do here should be dropping PPS_MAX_SOURCES at all! >> >> Let me go deeper in this issue. I'm going to produce a patch set in next days. Have you any chances to test it? >> >> Ciao, >> >> Rodolfo >> > MINORMASK > I'll have to check when the system we used for testing is available again (not easy to find a system with 20+ Ethernet ports) but I'd be happy to test a patch! Great! Please, let me know. > I know an increase to PPS_MAX_SOURCES was tested on that system. I see and it seems that it's safer to set PPS_MAX_SOURCES to MINORMASK... so please reproduce your patch with this simple modification, then I'm going to produce a patch to drop the PPS_MAX_SOURCES define since it's not needed anymore. After that you should test all these modifications in order to safely add them to Linux. Ciao, Rodolfo -- GNU/Linux Solutions e-mail: giometti@enneenne.com Linux Device Driver giometti@linux.it Embedded Systems phone: +39 349 2432127 UNIX programming skype: rodolfo.giometti