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 <arnaud.pouliquen@xxxxxxxxxxx> >> --- >> 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 >>