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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC530C433F5 for ; Tue, 5 Oct 2021 16:22:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7B9361381 for ; Tue, 5 Oct 2021 16:22:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236482AbhJEQYf (ORCPT ); Tue, 5 Oct 2021 12:24:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44564 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236107AbhJEQYe (ORCPT ); Tue, 5 Oct 2021 12:24:34 -0400 Received: from mail-ot1-x336.google.com (mail-ot1-x336.google.com [IPv6:2607:f8b0:4864:20::336]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F69AC061749 for ; Tue, 5 Oct 2021 09:22:43 -0700 (PDT) Received: by mail-ot1-x336.google.com with SMTP id j11-20020a9d190b000000b00546fac94456so26556283ota.6 for ; Tue, 05 Oct 2021 09:22:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=0iDxCDUbJZEtsInCF0VI19qSw9EILeIM3q4Rb38pchY=; b=KnVGpJA6MNPtFCXwf0kBZTz96mduFZVvNvXpZfVohdcldJ7O1xlDVYEHYC4wrQfn/5 ApCIB3b/I1swSE2sQe2vl4CMl4OmOitNBE/pG1MlgPuQfR5vQO/yszMbmkpBgf228os9 eLh4gL/ZubXxV7jnuIvBL8F99rtjSwNbLrEnnZCKm/IiuwXF/ZcMGMOzkg1h9WMDeISI NmGuLmObZJqApXR/0H11SOt9ygQaehi06OD0nNmzkAzPQDrgrkygLwamz8eR1ifBfw3e /1xwuRXYT6r48pgCYHOg47nbHOSkN3OSkqlSnXLGprupaDaxhaLrbh+zzmf+rlKsTcvv KV3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=0iDxCDUbJZEtsInCF0VI19qSw9EILeIM3q4Rb38pchY=; b=rRxzEENGBE8WZFJXPRqT4ogaeNyH1dfovBEHIFBdgjtxF6I773DnXuRDRuKdBA2mxu 9hy1s2l1JEt6ybjx/9D1SCwrN+Zz+B6VE3eHIsXgpSfpwu8GCczWseqw5cj3jvnBKLRW IfxKsaRJK6zVlQtSAf4w3q8ZEcX2dtUcnu64IiqKrhXjAskIiPo9Xr/QbdOjw102oc2c rTrOSmEcHkEt+grqgix6baqCSgIn+DHsmyLAMzIuDCKwIXuzB++2GfbG0RtxjComuXe9 i7JCWH+EHNmwKSDDjyFvzsn2d1Wq6A4yHqurHw3IBJqmZMs4owogmZ8G2mvg0jbTltE4 Rr/Q== X-Gm-Message-State: AOAM533VIz9ccgkfdc+ftIcmiGNuS7yAzvMOENzBscz9stvB/gXFA9Ql 59gV+rNnzFuT5XYj/N2Y65/yAQ== X-Google-Smtp-Source: ABdhPJyZ718hxVqtaUzE40mz8eqAfaT/bHp4zD0AuXZRWu/Vb3gXElvYwkWZ//QuEF2LaWFpOQST/g== X-Received: by 2002:a9d:3ae:: with SMTP id f43mr14671393otf.320.1633450961314; Tue, 05 Oct 2021 09:22:41 -0700 (PDT) Received: from ripper ([2600:1700:a0:3dc8:205:1bff:fec0:b9b3]) by smtp.gmail.com with ESMTPSA id i25sm3649241oto.26.2021.10.05.09.22.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Oct 2021 09:22:40 -0700 (PDT) Date: Tue, 5 Oct 2021 09:24:23 -0700 From: Bjorn Andersson To: Arnaud POULIQUEN Cc: Ohad Ben-Cohen , Jonathan Corbet , Mathieu Poirier , Greg Kroah-Hartman , Jiri Slaby , Suman Anna , linux-stm32@st-md-mailman.stormreply.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-remoteproc@vger.kernel.org Subject: Re: [PATCH v8 2/2] tty: add rpmsg driver Message-ID: References: <20210930160520.19678-1-arnaud.pouliquen@foss.st.com> <20210930160520.19678-3-arnaud.pouliquen@foss.st.com> <04f62e46-74ca-b7b5-a229-fdf6651343be@foss.st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04f62e46-74ca-b7b5-a229-fdf6651343be@foss.st.com> Precedence: bulk List-ID: X-Mailing-List: linux-remoteproc@vger.kernel.org On Tue 05 Oct 09:00 PDT 2021, Arnaud POULIQUEN wrote: > Hello Bjorn, > > On 10/4/21 10:12 PM, Bjorn Andersson wrote: > > On Thu 30 Sep 09:05 PDT 2021, Arnaud Pouliquen wrote: > > > >> This driver exposes a standard TTY interface on top of the rpmsg > >> framework through a rpmsg service. > >> > >> This driver supports multi-instances, offering a /dev/ttyRPMSGx entry > >> per rpmsg endpoint. > >> > > > > I think this looks pretty good, but it's a while since we discussed > > this, reading your patches again makes me wonder: > > That's fair, the last discussion on the topic was over a year ago. > > > > > 1) With all the efforts related to virtualization and adding things such > > as I2C support there, what are the merits of putting a tty driver ontop > > of rpmsg in comparison with directly on virtio - which would be used for > > virtualization as well. > > As mentionned in the cover letter, the main advantage of the RPMsg vs virtio is > that RPMsg is able to mix the services on an unique virtio instance. Using > Virtio console implies to add a new virtio instance for each service (or > instance of a service) with associated mailbox channels. > Taking advantage of the RPMsg service mixing is important for platform (such as > stm32MP1) on which coprocessor is limited in term of memory mapping. > The limitations related to mapping additional virtio pipes does seem like a reasonable one. I just hope we don't end up duplicating much of the virtualization effort, with the recently concluded I2C client support coming to mind. > I also expect that this service would be available for some other backend than > the virtio one. > Last time we discussed this I believe I mentioned the AT command channels found in Qualcomm modems. Since then that got pushed into drivers/net/wwan, for the few other cases rpmsg_char works fine. > > > > 2) What prevents you from pointing your userspace tool at an rpmsg_char > > endpoint? > > You are right rpmsg_char could be an alternative. But advantage of the TTY is: > > - It possible to reuse existing applications/tools relying on TTY devices. > An example is a TTY RPMSG device dedicated for coprocessor traces that can be > simply redirect to a log file or mixed to the kernel logs by scripts. > Another exemple is the ability to ease migration from a 2-processors system > solution (with UART-based IPC) to a system solution with an internal > coprocessor. We received such requirement from some ST customers. > I presume the transport itself provided by rpmsg_char would work just fine for this, but that these applications expects something from the tty framework, with its known ioctls etc? > - For rpmsg_char you have to share device between TX and RX (only one fopen > allowed per device), while TTY allows you to manage one device in 2 independent > threads/appliaction. > At least in the Qualcomm case, where the channels have a state and clients opening and closing the rpmsg_char will affect that state it simplifies things a lot not to support a multi-client model. So I think there's merit to this difference. > - TTY framework manages intermediate buffer that allow to free Rx RPMsg buffers. > rpmsg_char does the same thing, by putting incoming messages on epddev->queue. > So rpmsg_char and rpmsg_tty don't seem to me to cover exactly the same requierement. > No, you're right there's some differences here. Regards, Bjorn > Thanks, > Arnaud > > > > > Thanks, > > Bjorn > > > >> Signed-off-by: Arnaud Pouliquen > >> --- > >> Documentation/serial/tty_rpmsg.rst | 15 ++ > >> drivers/tty/Kconfig | 9 + > >> drivers/tty/Makefile | 1 + > >> drivers/tty/rpmsg_tty.c | 275 +++++++++++++++++++++++++++++ > >> 4 files changed, 300 insertions(+) > >> create mode 100644 Documentation/serial/tty_rpmsg.rst > >> create mode 100644 drivers/tty/rpmsg_tty.c > >> > >> diff --git a/Documentation/serial/tty_rpmsg.rst b/Documentation/serial/tty_rpmsg.rst > >> new file mode 100644 > >> index 000000000000..b055107866c9 > >> --- /dev/null > >> +++ b/Documentation/serial/tty_rpmsg.rst > >> @@ -0,0 +1,15 @@ > >> +.. SPDX-License-Identifier: GPL-2.0 > >> + > >> +========= > >> +RPMsg TTY > >> +========= > >> + > >> +The rpmsg tty driver implements serial communication on the RPMsg bus to makes possible for > >> +user-space programs to send and receive rpmsg messages as a standard tty protocol. > >> + > >> +The remote processor can instantiate a new tty by requesting a "rpmsg-tty" RPMsg service. > >> + > >> +The "rpmsg-tty" service is directly used for data exchange. No flow control is implemented. > >> + > >> +Information related to the RPMsg and associated tty device is available in > >> +/sys/bus/rpmsg/devices/. > >> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig > >> index 23cc988c68a4..5095513029d7 100644 > >> --- a/drivers/tty/Kconfig > >> +++ b/drivers/tty/Kconfig > >> @@ -368,6 +368,15 @@ config VCC > >> > >> source "drivers/tty/hvc/Kconfig" > >> > >> +config RPMSG_TTY > >> + tristate "RPMSG tty driver" > >> + depends on RPMSG > >> + help > >> + Say y here to export rpmsg endpoints as tty devices, usually found > >> + in /dev/ttyRPMSGx. > >> + This makes it possible for user-space programs to send and receive > >> + rpmsg messages as a standard tty protocol. > >> + > >> endif # TTY > >> > >> source "drivers/tty/serdev/Kconfig" > >> diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile > >> index a2bd75fbaaa4..07aca5184a55 100644 > >> --- a/drivers/tty/Makefile > >> +++ b/drivers/tty/Makefile > >> @@ -26,5 +26,6 @@ obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o > >> obj-$(CONFIG_GOLDFISH_TTY) += goldfish.o > >> obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o > >> obj-$(CONFIG_VCC) += vcc.o > >> +obj-$(CONFIG_RPMSG_TTY) += rpmsg_tty.o > >> > >> obj-y += ipwireless/ > >> diff --git a/drivers/tty/rpmsg_tty.c b/drivers/tty/rpmsg_tty.c > >> new file mode 100644 > >> index 000000000000..0c99f54c2911 > >> --- /dev/null > >> +++ b/drivers/tty/rpmsg_tty.c > >> @@ -0,0 +1,275 @@ > >> +// SPDX-License-Identifier: GPL-2.0 > >> +/* > >> + * Copyright (C) STMicroelectronics 2021 - All Rights Reserved > >> + */ > >> + > >> +#include > >> +#include > >> +#include > >> +#include > >> +#include > >> + > >> +#define MAX_TTY_RPMSG 32 > >> + > >> +static DEFINE_IDR(tty_idr); /* tty instance id */ > >> +static DEFINE_MUTEX(idr_lock); /* protects tty_idr */ > >> + > >> +static struct tty_driver *rpmsg_tty_driver; > >> + > >> +struct rpmsg_tty_port { > >> + struct tty_port port; /* TTY port data */ > >> + int id; /* TTY rpmsg index */ > >> + struct rpmsg_device *rpdev; /* rpmsg device */ > >> +}; > >> + > >> +static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src) > >> +{ > >> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev); > >> + int copied; > >> + > >> + if (!len) > >> + return -EINVAL; > >> + copied = tty_insert_flip_string(&cport->port, data, len); > >> + if (copied != len) > >> + dev_dbg(&rpdev->dev, "Trunc buffer: available space is %d\n", > >> + copied); > >> + tty_flip_buffer_push(&cport->port); > >> + > >> + return 0; > >> +} > >> + > >> +static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty) > >> +{ > >> + struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index); > >> + > >> + if (!cport) { > >> + dev_err(tty->dev, "Cannot get cport\n"); > >> + return -ENODEV; > >> + } > >> + > >> + tty->driver_data = cport; > >> + > >> + return tty_port_install(&cport->port, driver, tty); > >> +} > >> + > >> +static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp) > >> +{ > >> + return tty_port_open(tty->port, tty, filp); > >> +} > >> + > >> +static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp) > >> +{ > >> + return tty_port_close(tty->port, tty, filp); > >> +} > >> + > >> +static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len) > >> +{ > >> + struct rpmsg_tty_port *cport = tty->driver_data; > >> + struct rpmsg_device *rpdev; > >> + int msg_max_size, msg_size; > >> + int ret; > >> + > >> + rpdev = cport->rpdev; > >> + > >> + dev_dbg(&rpdev->dev, "Send msg from tty->index = %d, len = %d\n", tty->index, len); > >> + > >> + msg_max_size = rpmsg_get_mtu(rpdev->ept); > >> + if (msg_max_size < 0) > >> + return msg_max_size; > >> + > >> + msg_size = min(len, msg_max_size); > >> + > >> + /* > >> + * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not > >> + * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM. > >> + */ > >> + ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size); > >> + if (ret) { > >> + dev_dbg(&rpdev->dev, "rpmsg_send failed: %d\n", ret); > >> + return ret; > >> + } > >> + > >> + return msg_size; > >> +} > >> + > >> +static unsigned int rpmsg_tty_write_room(struct tty_struct *tty) > >> +{ > >> + struct rpmsg_tty_port *cport = tty->driver_data; > >> + int size; > >> + > >> + size = rpmsg_get_mtu(cport->rpdev->ept); > >> + if (size < 0) > >> + return 0; > >> + > >> + return size; > >> +} > >> + > >> +static const struct tty_operations rpmsg_tty_ops = { > >> + .install = rpmsg_tty_install, > >> + .open = rpmsg_tty_open, > >> + .close = rpmsg_tty_close, > >> + .write = rpmsg_tty_write, > >> + .write_room = rpmsg_tty_write_room, > >> +}; > >> + > >> +static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void) > >> +{ > >> + struct rpmsg_tty_port *cport; > >> + int err; > >> + > >> + cport = kzalloc(sizeof(*cport), GFP_KERNEL); > >> + if (!cport) > >> + return ERR_PTR(-ENOMEM); > >> + > >> + mutex_lock(&idr_lock); > >> + cport->id = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL); > >> + mutex_unlock(&idr_lock); > >> + > >> + if (cport->id < 0) { > >> + err = cport->id; > >> + kfree(cport); > >> + return ERR_PTR(err); > >> + } > >> + > >> + return cport; > >> +} > >> + > >> +static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport) > >> +{ > >> + mutex_lock(&idr_lock); > >> + idr_remove(&tty_idr, cport->id); > >> + mutex_unlock(&idr_lock); > >> + > >> + kfree(cport); > >> +} > >> + > >> +static const struct tty_port_operations rpmsg_tty_port_ops = { }; > >> + > >> +static int rpmsg_tty_probe(struct rpmsg_device *rpdev) > >> +{ > >> + struct rpmsg_tty_port *cport; > >> + struct device *dev = &rpdev->dev; > >> + struct device *tty_dev; > >> + int ret; > >> + > >> + cport = rpmsg_tty_alloc_cport(); > >> + if (IS_ERR(cport)) { > >> + dev_err(dev, "Failed to alloc tty port\n"); > >> + return PTR_ERR(cport); > >> + } > >> + > >> + tty_port_init(&cport->port); > >> + cport->port.ops = &rpmsg_tty_port_ops; > >> + > >> + tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver, > >> + cport->id, dev); > >> + if (IS_ERR(tty_dev)) { > >> + dev_err(dev, "Failed to register tty port\n"); > >> + ret = PTR_ERR(tty_dev); > >> + goto err_destroy; > >> + } > >> + > >> + cport->rpdev = rpdev; > >> + > >> + dev_set_drvdata(dev, cport); > >> + > >> + dev_dbg(dev, "New channel: 0x%x -> 0x%x : ttyRPMSG%d\n", > >> + rpdev->src, rpdev->dst, cport->id); > >> + > >> + return 0; > >> + > >> +err_destroy: > >> + tty_port_destroy(&cport->port); > >> + rpmsg_tty_release_cport(cport); > >> + > >> + return ret; > >> +} > >> + > >> +static void rpmsg_tty_remove(struct rpmsg_device *rpdev) > >> +{ > >> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev); > >> + > >> + dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id); > >> + > >> + /* User hang up to release the tty */ > >> + if (tty_port_initialized(&cport->port)) > >> + tty_port_tty_hangup(&cport->port, false); > >> + > >> + tty_unregister_device(rpmsg_tty_driver, cport->id); > >> + > >> + tty_port_destroy(&cport->port); > >> + rpmsg_tty_release_cport(cport); > >> +} > >> + > >> +static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = { > >> + { .name = "rpmsg-tty" }, > >> + { }, > >> +}; > >> +MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table); > >> + > >> +static struct rpmsg_driver rpmsg_tty_rpmsg_drv = { > >> + .drv.name = KBUILD_MODNAME, > >> + .id_table = rpmsg_driver_tty_id_table, > >> + .probe = rpmsg_tty_probe, > >> + .callback = rpmsg_tty_cb, > >> + .remove = rpmsg_tty_remove, > >> +}; > >> + > >> +static int __init rpmsg_tty_init(void) > >> +{ > >> + int err; > >> + > >> + rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW | > >> + TTY_DRIVER_DYNAMIC_DEV); > >> + if (IS_ERR(rpmsg_tty_driver)) > >> + return PTR_ERR(rpmsg_tty_driver); > >> + > >> + rpmsg_tty_driver->driver_name = "rpmsg_tty"; > >> + rpmsg_tty_driver->name = "ttyRPMSG"; > >> + rpmsg_tty_driver->major = 0; > >> + rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE; > >> + > >> + /* Disable unused mode by default */ > >> + rpmsg_tty_driver->init_termios = tty_std_termios; > >> + rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON); > >> + rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR); > >> + > >> + tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops); > >> + > >> + err = tty_register_driver(rpmsg_tty_driver); > >> + if (err < 0) { > >> + pr_err("Couldn't install rpmsg tty driver: err %d\n", err); > >> + goto error_put; > >> + } > >> + > >> + err = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv); > >> + if (err < 0) { > >> + pr_err("Couldn't register rpmsg tty driver: err %d\n", err); > >> + goto error_unregister; > >> + } > >> + > >> + return 0; > >> + > >> +error_unregister: > >> + tty_unregister_driver(rpmsg_tty_driver); > >> + > >> +error_put: > >> + tty_driver_kref_put(rpmsg_tty_driver); > >> + > >> + return err; > >> +} > >> + > >> +static void __exit rpmsg_tty_exit(void) > >> +{ > >> + unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv); > >> + tty_unregister_driver(rpmsg_tty_driver); > >> + tty_driver_kref_put(rpmsg_tty_driver); > >> + idr_destroy(&tty_idr); > >> +} > >> + > >> +module_init(rpmsg_tty_init); > >> +module_exit(rpmsg_tty_exit); > >> + > >> +MODULE_AUTHOR("Arnaud Pouliquen "); > >> +MODULE_DESCRIPTION("remote processor messaging tty driver"); > >> +MODULE_LICENSE("GPL v2"); > >> -- > >> 2.17.1 > >>