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Mon, 21 Jun 2021 11:35:57 +0200 (CEST) Received: from Webmail-eu.st.com (sfhdag2node3.st.com [10.75.127.6]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 3035321CA90; Mon, 21 Jun 2021 11:35:57 +0200 (CEST) Received: from lmecxl0889.lme.st.com (10.75.127.48) by SFHDAG2NODE3.st.com (10.75.127.6) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 21 Jun 2021 11:35:56 +0200 Subject: Re: [PATCH 1/4] rpmsg: ctrl: Introduce RPMSG_CREATE_DEV_IOCTL From: Arnaud POULIQUEN To: Mathieu Poirier CC: Bjorn Andersson , Ohad Ben-Cohen , , , References: <20210604091406.15901-1-arnaud.pouliquen@foss.st.com> <20210604091406.15901-2-arnaud.pouliquen@foss.st.com> <20210615175334.GD604521@p14s> <1645a516-1d83-27bd-e9ed-c78a18bf4c52@foss.st.com> Message-ID: Date: Mon, 21 Jun 2021 11:35:56 +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: <1645a516-1d83-27bd-e9ed-c78a18bf4c52@foss.st.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.48] X-ClientProxiedBy: SFHDAG2NODE1.st.com (10.75.127.4) To SFHDAG2NODE3.st.com (10.75.127.6) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-06-21_03:2021-06-20,2021-06-21 signatures=0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/16/21 10:12 AM, Arnaud POULIQUEN wrote: > Hello Mathieu, > > On 6/15/21 7:53 PM, Mathieu Poirier wrote: >> On Fri, Jun 04, 2021 at 11:14:03AM +0200, Arnaud Pouliquen wrote: >>> Implement the RPMSG_CREATE_DEV_IOCTL to allow the user application to >>> initiate a communication through a new rpmsg channel. >>> This Ioctl can be used to instantiate a local rpmsg device. >>> Depending on the back-end implementation, the associated rpmsg driver is >>> probed and a NS announcement can be sent to the remote processor. >>> >>> Suggested-by: Mathieu Poirier >>> Signed-off-by: Arnaud Pouliquen >>> --- >>> drivers/rpmsg/rpmsg_ctrl.c | 30 ++++++++++++++++++++++++++---- >>> include/uapi/linux/rpmsg.h | 5 +++++ >>> 2 files changed, 31 insertions(+), 4 deletions(-) >>> >>> diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c >>> index eeb1708548c1..4aa962df3661 100644 >>> --- a/drivers/rpmsg/rpmsg_ctrl.c >>> +++ b/drivers/rpmsg/rpmsg_ctrl.c >>> @@ -23,6 +23,7 @@ >>> #include >>> >>> #include "rpmsg_char.h" >>> +#include "rpmsg_internal.h" >>> >>> static dev_t rpmsg_major; >>> >>> @@ -37,11 +38,13 @@ static DEFINE_IDA(rpmsg_minor_ida); >>> * @rpdev: underlaying rpmsg device >>> * @cdev: cdev for the ctrl device >>> * @dev: device for the ctrl device >>> + * @ctrl_lock: serialize the ioctrls. >>> */ >>> struct rpmsg_ctrldev { >>> struct rpmsg_device *rpdev; >>> struct cdev cdev; >>> struct device dev; >>> + struct mutex ctrl_lock; >>> }; >>> >>> static int rpmsg_ctrldev_open(struct inode *inode, struct file *filp) >>> @@ -70,9 +73,8 @@ static long rpmsg_ctrldev_ioctl(struct file *fp, unsigned int cmd, >>> void __user *argp = (void __user *)arg; >>> struct rpmsg_endpoint_info eptinfo; >>> struct rpmsg_channel_info chinfo; >>> - >>> - if (cmd != RPMSG_CREATE_EPT_IOCTL) >>> - return -EINVAL; >>> + struct rpmsg_device *rpdev; >>> + int ret = 0; >>> >>> if (copy_from_user(&eptinfo, argp, sizeof(eptinfo))) >>> return -EFAULT; >>> @@ -82,7 +84,26 @@ static long rpmsg_ctrldev_ioctl(struct file *fp, unsigned int cmd, >>> chinfo.src = eptinfo.src; >>> chinfo.dst = eptinfo.dst; >>> >>> - return rpmsg_chrdev_eptdev_create(ctrldev->rpdev, &ctrldev->dev, chinfo); >>> + mutex_lock(&ctrldev->ctrl_lock); >> >> Do we need a lock here? I thought the character device layer would guarantee >> accesses on a file handler would be atomic... Am I wrong? >> > > It is a good point! from my understanding, using "unlocked_ioctl" ops, the > driver has to handle is own atomic protection. > I will try to hack the code to verify this. I confirm without lock there is no atomic access, re-entrance is possible in rpmsg_ctrldev_ioctl. Keeping lock to serialize the controls seems safer to me to avoid race condition. Regards Arnaud > > Thanks, > Arnaud > >>> + switch (cmd) { >>> + case RPMSG_CREATE_EPT_IOCTL: >>> + ret = rpmsg_chrdev_eptdev_create(ctrldev->rpdev, &ctrldev->dev, chinfo); >>> + break; >>> + >>> + case RPMSG_CREATE_DEV_IOCTL: >>> + rpdev = rpmsg_create_channel(ctrldev->rpdev, &chinfo); >>> + if (!rpdev) { >>> + dev_err(&ctrldev->dev, "failed to create %s channel\n", chinfo.name); >>> + ret = -ENXIO; >>> + } >>> + break; >>> + >>> + default: >>> + ret = -EINVAL; >>> + } >>> + mutex_unlock(&ctrldev->ctrl_lock); >>> + >>> + return ret; >>> }; >>> >>> static const struct file_operations rpmsg_ctrldev_fops = { >>> @@ -119,6 +140,7 @@ static int rpmsg_ctrldev_probe(struct rpmsg_device *rpdev) >>> device_initialize(dev); >>> dev->parent = &rpdev->dev; >>> >>> + mutex_init(&ctrldev->ctrl_lock); >>> cdev_init(&ctrldev->cdev, &rpmsg_ctrldev_fops); >>> ctrldev->cdev.owner = THIS_MODULE; >>> >>> diff --git a/include/uapi/linux/rpmsg.h b/include/uapi/linux/rpmsg.h >>> index f5ca8740f3fb..f9d5a74e7801 100644 >>> --- a/include/uapi/linux/rpmsg.h >>> +++ b/include/uapi/linux/rpmsg.h >>> @@ -33,4 +33,9 @@ struct rpmsg_endpoint_info { >>> */ >>> #define RPMSG_DESTROY_EPT_IOCTL _IO(0xb5, 0x2) >>> >>> +/** >>> + * Instantiate a rpmsg service device. >>> + */ >>> +#define RPMSG_CREATE_DEV_IOCTL _IOW(0xb5, 0x3, struct rpmsg_endpoint_info) >>> + >>> #endif >>> -- >>> 2.17.1 >>>