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=-15.2 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 CBE67C48BE8 for ; Wed, 16 Jun 2021 12:38:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9E5560249 for ; Wed, 16 Jun 2021 12:38:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232421AbhFPMks (ORCPT ); Wed, 16 Jun 2021 08:40:48 -0400 Received: from mx08-00178001.pphosted.com ([91.207.212.93]:13224 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229456AbhFPMkm (ORCPT ); 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Wed, 16 Jun 2021 14:38:28 +0200 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id D73B510002A; Wed, 16 Jun 2021 14:38:27 +0200 (CEST) Received: from Webmail-eu.st.com (sfhdag2node3.st.com [10.75.127.6]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id BE41D226FC4; Wed, 16 Jun 2021 14:38:27 +0200 (CEST) Received: from lmecxl0889.lme.st.com (10.75.127.51) by SFHDAG2NODE3.st.com (10.75.127.6) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 16 Jun 2021 14:38:27 +0200 Subject: Re: [PATCH 3/4] rpmsg: char: Introduce the "rpmsg-raw" channel To: Mathieu Poirier CC: Bjorn Andersson , Ohad Ben-Cohen , , , , References: <20210607173032.30133-1-arnaud.pouliquen@foss.st.com> <20210607173032.30133-4-arnaud.pouliquen@foss.st.com> <20210615200102.GE604521@p14s> From: Arnaud POULIQUEN Message-ID: Date: Wed, 16 Jun 2021 14:38:26 +0200 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: <20210615200102.GE604521@p14s> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.51] X-ClientProxiedBy: SFHDAG1NODE2.st.com (10.75.127.2) To SFHDAG2NODE3.st.com (10.75.127.6) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-16_07:2021-06-15,2021-06-16 signatures=0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mathieu, On 6/15/21 10:01 PM, Mathieu Poirier wrote: > On Mon, Jun 07, 2021 at 07:30:31PM +0200, Arnaud Pouliquen wrote: >> Allows to probe the endpoint device on a remote name service announcement, >> by registering a rpmsg_driverfor the "rpmsg-raw" channel. >> >> With this patch the /dev/rpmsgX interface can be instantiated by the remote >> firmware. >> >> Signed-off-by: Arnaud Pouliquen >> --- >> drivers/rpmsg/rpmsg_char.c | 54 ++++++++++++++++++++++++++++++++++++-- >> 1 file changed, 52 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c >> index 4199ac1bee10..3b850b218eb0 100644 >> --- a/drivers/rpmsg/rpmsg_char.c >> +++ b/drivers/rpmsg/rpmsg_char.c >> @@ -25,6 +25,8 @@ >> >> #include "rpmsg_char.h" >> >> +#define RPMSG_CHAR_DEVNAME "rpmsg-raw" >> + >> static dev_t rpmsg_major; >> static struct class *rpmsg_class; >> >> @@ -416,6 +418,40 @@ int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct device *parent >> } >> EXPORT_SYMBOL(rpmsg_chrdev_eptdev_create); >> >> +static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev) >> +{ >> + struct rpmsg_channel_info chinfo; >> + >> + memcpy(chinfo.name, RPMSG_CHAR_DEVNAME, sizeof(RPMSG_CHAR_DEVNAME)); >> + chinfo.src = rpdev->src; >> + chinfo.dst = rpdev->dst; >> + >> + return __rpmsg_chrdev_eptdev_create(rpdev, &rpdev->dev, chinfo, true); > > I am a little puzzled here as to why we need different modes... Why can't we > simply call rpmsg_chrdev_eptdev_create() and let the endpoint be created on > open() and destroyed on release() as per the current implementation? The main reason is the support of the NS announcement a NS announcement is received from the remote processor: channel name: "rpmsg-raw" remote address (dst address): 0x400 local address (scr address) : RPMSG_ADDR_ANY => no default endpoint, and not local address. case 1) if we use legacy implementation ( no default endpoint) => create/destroy endpoint on open/stop - on first open: created endpoint is bound to scr address 0x406 - a first message is sent to the remote side, the address 0x406 is stored as default channel dst address on remote side. - on close: endpoint is closed and associated address 0x406 is free. - another driver create an enpoint the address 0x406 is reserved for this new endpoint. - on new open: scr address is set to next value 0x407 => how to inform remote processor that the address has changed? => no reservation mechanism that ensure that you can reuse the same address case 2) relying on use_default_ept => Ensure that both side have always the same addresses to communicate. > > I'd rather keep things simple for the refactoring and introduce new features > later if need be. Yes I agree with you, but here it could become a nightmare for the remote processor if the Linux endpoint address is not stable. Anyway we can consider this as a workaround waiting the extension of the NS announcement to have a better management of the address exchange on channel initialization. Thanks Arnaud > > As I said, it may be that I don't understand the usecase. > > Thanks, > Mathieu > >> +} >> + >> +static void rpmsg_chrdev_remove(struct rpmsg_device *rpdev) >> +{ >> + int ret; >> + >> + ret = device_for_each_child(&rpdev->dev, NULL, rpmsg_chrdev_eptdev_destroy); >> + if (ret) >> + dev_warn(&rpdev->dev, "failed to destroy endpoints: %d\n", ret); >> +} >> + >> +static struct rpmsg_device_id rpmsg_chrdev_id_table[] = { >> + { .name = RPMSG_CHAR_DEVNAME }, >> + { }, >> +}; >> + >> +static struct rpmsg_driver rpmsg_chrdev_driver = { >> + .probe = rpmsg_chrdev_probe, >> + .remove = rpmsg_chrdev_remove, >> + .id_table = rpmsg_chrdev_id_table, >> + .drv = { >> + .name = "rpmsg_chrdev", >> + }, >> +}; >> + >> static int rpmsg_chrdev_init(void) >> { >> int ret; >> @@ -429,16 +465,30 @@ static int rpmsg_chrdev_init(void) >> rpmsg_class = class_create(THIS_MODULE, "rpmsg"); >> if (IS_ERR(rpmsg_class)) { >> pr_err("failed to create rpmsg class\n"); >> - unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX); >> - return PTR_ERR(rpmsg_class); >> + ret = PTR_ERR(rpmsg_class); >> + goto free_region; >> + } >> + >> + ret = register_rpmsg_driver(&rpmsg_chrdev_driver); >> + if (ret < 0) { >> + pr_err("rpmsg: failed to register rpmsg raw driver\n"); >> + goto free_class; >> } >> >> return 0; >> + >> +free_class: >> + class_destroy(rpmsg_class); >> +free_region: >> + unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX); >> + >> + return ret; >> } >> postcore_initcall(rpmsg_chrdev_init); >> >> static void rpmsg_chrdev_exit(void) >> { >> + unregister_rpmsg_driver(&rpmsg_chrdev_driver); >> class_destroy(rpmsg_class); >> unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX); >> } >> -- >> 2.17.1 >>