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[68.147.0.187]) by smtp.gmail.com with ESMTPSA id s12sm1376462pjz.37.2021.06.22.13.30.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Jun 2021 13:30:21 -0700 (PDT) Date: Tue, 22 Jun 2021 14:30:19 -0600 From: Mathieu Poirier To: Arnaud POULIQUEN Cc: Bjorn Andersson , Ohad Ben-Cohen , linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, julien.massot@iot.bzh Subject: Re: [PATCH 3/4] rpmsg: char: Introduce the "rpmsg-raw" channel Message-ID: <20210622203019.GB1006507@p14s> References: <20210607173032.30133-1-arnaud.pouliquen@foss.st.com> <20210607173032.30133-4-arnaud.pouliquen@foss.st.com> <20210615200102.GE604521@p14s> <20210617213154.GA790564@p14s> <20210621223852.GA980846@p14s> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 22, 2021 at 10:21:02AM +0200, Arnaud POULIQUEN wrote: > > > On 6/22/21 12:38 AM, Mathieu Poirier wrote: > > On Fri, Jun 18, 2021 at 01:35:43PM +0200, Arnaud POULIQUEN wrote: > >> Hi Mathieu, > >> > >> On 6/17/21 11:31 PM, Mathieu Poirier wrote: > >>> On Wed, Jun 16, 2021 at 02:38:26PM +0200, Arnaud POULIQUEN wrote: > >>>> 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 see the problem and your solution is adequate - I think the code simply needs > >>> to be moved around a little. Here is what I suggest: > >>> > >>> 1) Create the endpoint in rpmsg_chrdev_probe(), just before calling > >>> rpmsg_chrdev_eptdev_create(). That way changes to rpmsg_eptdev_open() can be > >>> kept to a minimum. I don't think we'll be needing > >>> __rpmsg_chrdev_eptdev_create() anymore. > >> > >> Yes i could, but this will break a concept of the rpmsg_char that creates the > >> endpoint on open, meaning that application is ready to communicate. > > > > In my opinion creating and destorying an endpoint on open/close is something we > > want to move away from. > > Not simple to answer... As discussed a mechanism is requested by some developer > to be able on a ns announcement to inform the remote side that the user > application or the client driver is ready to communicate, the endpoint creation > could be the trigger. > > That said, let's go by steps. For this patchset I will try to come back to my > first implementation where i created the endpoint on probe. Going back to that conversation I realise the directions I gave out on that front was not optimal. As you mention above please go back to creating the endpoint on probe(). > > > > >> > >> I would rather preserve this behavior. > >> > >>> > >>> 2) We can get rid of use_default_ept by taking advantage of the fact that the > >>> rpmsg_char driver does not use rpmsg_device::ept. If we create the endpoint in > >>> rpmsg_chrdev_probe() we know that if rpdev->ept exists, we must not create > >>> or destroy the endpoint in rpmsg_eptdev_open() and rpmsg_eptdev_release(). > >>> > >>> 3) Function rpmsg_eptdev_open() doesn't change much. If rpdev->ept is NULL > >>> than > >>> an endpoint is created as the current implementation. Otherwise we simply do: > >>> > >>> eptdev->ept = rpdev->ept; > >>> > >> > >> In qcom_glink_create_chrdev, a rpmsg_ctrl rpdev with a default endpoint is > >> created and used as parameter of the pmsg_ctrldev_register_device [1] > >> => rpdev->ept is not NULL. > >> > >> So the rpmsg_char has to differentiate 2 cases on rpmsg_eptdev_open: > >> - A enpdoint has to be created as requested by RPMSG_CREATE_EPT_IOCTL > >> (regardless of the rpdev->ept value) > >> - for a rpmsg device created by an NS announcement: A default endpoint has to be > >> reused (or created if rpdev->ept is null). > >> > >> so the rpdev->ept test is not relevant for decision, the use_default_ept ( or > >> another flag) is mandatory. > > > > Yes, we need a flag. May I suggest "fixed_ept" rather than "used_default_ept"? > > "fixed_ept" could be miss-understood . It can be interpreted as an endpoint with > a fixed address (not set to RPMSG_ADDR_ANY). > What about "default_ept" or "static_ept"? I'll take static_ept. > > Thanks > Arnaud > > > > >> > >> > >>> 4) Make sure the teardown path works as well. From what I can see, it should. > >>> > >>> 5) Add a __lot__ of comments. > >>> > >>> If the above all works this entire patchset should become really small. > >> > >> Thanks, > >> Arnaud > >> > >>> > >>>> > >>>>> > >>>>> 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 > >>>>>>