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 X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9A4DC43381 for ; Thu, 21 Feb 2019 17:18:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 934582083B for ; Thu, 21 Feb 2019 17:18:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728583AbfBURS3 (ORCPT ); Thu, 21 Feb 2019 12:18:29 -0500 Received: from mx-ginzinger.sigmacloud.services ([185.154.235.147]:55528 "EHLO mx-ginzinger.sigmacloud.services" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726232AbfBURS3 (ORCPT ); Thu, 21 Feb 2019 12:18:29 -0500 Received: from [31.193.165.228] (port=9228 helo=mx-ginzinger.sigmacloud.services) by mx-ginzinger.sigmacloud.services with esmtps (TLSv1.2:AES256-GCM-SHA384:256) (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1gwrzH-00028o-2Y; Thu, 21 Feb 2019 18:18:19 +0100 Received: from martin-laptop.buero.ginzinger.com (10.10.1.120) by exc1.buero.ginzinger.com (10.1.1.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1466.3; Thu, 21 Feb 2019 18:18:19 +0100 X-CTCH-RefID: str=0001.0A0B020F.5C6EDD5B.0066,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 From: Martin Kepplinger To: , , , , , , , , , , , , , , CC: , Martin Kepplinger Subject: [PATCH v2 1/9] serial: uapi: add SER_RS485_DELAY_IN_USEC flag to struct serial_rs485 Date: Thu, 21 Feb 2019 18:17:50 +0100 Message-ID: <20190221171758.10322-1-martin.kepplinger@ginzinger.com> X-Mailer: git-send-email 2.20.1 X-Originating-IP: [10.10.1.120] X-ClientProxiedBy: exc1.buero.ginzinger.com (10.1.1.204) To exc1.buero.ginzinger.com (10.1.1.204) X-EXCLAIMER-MD-ORIGINAL-SUBJECT: [NOSIG][NODISC][PATCH v2 1/9] serial: uapi: add SER_RS485_DELAY_IN_USEC flag to struct serial_rs485 X-EXCLAIMER-MD-CONFIG: 9dd172f7-de2e-4231-b886-ec11f46e03b3 MIME-Version: 1.0 Content-Type: multipart/signed; protocol="application/x-pkcs7-signature"; micalg="sha-256"; boundary="----9F773A4BFF92DF307DDF747586A784E5" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an S/MIME signed message ------9F773A4BFF92DF307DDF747586A784E5 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain This extends the user interface for rs485 communication: We add a new flag, SER_RS485_DELAY_IN_USEC, to struct serial_rs485 that indicates that delay_rts_before_send and delay_rts_after_send values are interpreted in microsecond units. Up until now, the code comment defined these values to hold the delays in millisecond units. Especially with fast data rates (1Mbaut or more) that are not too uncommon for RS485, 1ms become quite long. Users need to be able to set shorter delays than 1 ms in order not to slow down the channel unnecessarily. So when delays are needed, but not as long as 1ms, this enables faster communication channels without changing the baudrate. Signed-off-by: Martin Kepplinger --- revision history ---------------- v2: re-send as a proper series after fixing my mailserver v1: initial implementation idea So have this totally quirky patch that uses udelay() in our tree for a looong time now because of the above reasons - and because we are lazy. This is an attempt to get rid of said patch on our side and fix this properly. What do you thing about adding a flag in general? The following patches should integrate this idea in devicetree and drivers. These changes are NOT tested on hardware but should behave predictably enough. I use the delays in a driver that doesn't implement them yet at all. I'll do that after this (or something similar) is merged - it's a 2-liner then. Also, a patch to the rs485conf tool, that is sometimes used instead of ioctl() directly, will be prepared as well. thanks martin include/uapi/linux/serial.h | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h index 93eb3c496ff1..c16c950ebca2 100644 --- a/include/uapi/linux/serial.h +++ b/include/uapi/linux/serial.h @@ -126,8 +126,15 @@ struct serial_rs485 { #define SER_RS485_TERMINATE_BUS (1 << 5) /* Enable bus termination (if supported) */ - __u32 delay_rts_before_send; /* Delay before send (milliseconds) */ - __u32 delay_rts_after_send; /* Delay after send (milliseconds) */ +#define SER_RS485_DELAY_IN_USEC (1 << 6) /* delay_rts_*_send + values are given in + microseconds */ + __u32 delay_rts_before_send; /* Delay before send (milliseconds + by default. microseconds if flag + is set) */ + __u32 delay_rts_after_send; /* Delay after send (milliseconds + by default. microseconds if flag + is set) */ __u32 padding[5]; /* Memory is cheap, new structs are a royal PITA .. */ }; -- 2.20.1 ------9F773A4BFF92DF307DDF747586A784E5 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" MIIOHAYJKoZIhvcNAQcCoIIODTCCDgkCAQExDzANBglghkgBZQMEAgEFADALBgkq hkiG9w0BBwGgggshMIIF5jCCA86gAwIBAgIQapvhODv/K2ufAdXZuKdSVjANBgkq hkiG9w0BAQwFADCBhTELMAkGA1UEBhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFu Y2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgGA1UEChMRQ09NT0RPIENBIExp bWl0ZWQxKzApBgNVBAMTIkNPTU9ETyBSU0EgQ2VydGlmaWNhdGlvbiBBdXRob3Jp dHkwHhcNMTMwMTEwMDAwMDAwWhcNMjgwMTA5MjM1OTU5WjCBlzELMAkGA1UEBhMC R0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9y ZDEaMBgGA1UEChMRQ09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBS U0EgQ2xpZW50IEF1dGhlbnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0EwggEi MA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQC+s55XrCh2dUAWxzgDmNPGGHYh UPMleQtMtaDRfTpYPpynMS6n9jR22YRq2tA9NEjk6vW7rN/5sYFLIP1of3l0NKZ6 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