From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 References: <20200310155058.1607-1-mathieu.poirier@linaro.org> <591bd727-32af-9ea2-8c46-98f46ee3711e@ti.com> <34d1277f-c35e-5df8-7d0c-ea1e961a127f@st.com> <20200327193602.GA22939@xps15> <77cba22f-5911-e88a-ec25-50cbe9b8fbbe@ti.com> In-Reply-To: <77cba22f-5911-e88a-ec25-50cbe9b8fbbe@ti.com> From: Mathieu Poirier Date: Wed, 8 Apr 2020 09:59:57 -0600 Message-ID: Subject: Re: [PATCH v2] rpmsg: core: Add wildcard match for name service Content-Type: text/plain; charset="UTF-8" To: Suman Anna Cc: Arnaud POULIQUEN , Ohad Ben-Cohen , Bjorn Andersson , linux-remoteproc , Linux Kernel Mailing List List-ID: On Tue, 7 Apr 2020 at 17:07, Suman Anna wrote: > > Hi Mathieu, Arnaud, > > On 3/27/20 2:36 PM, Mathieu Poirier wrote: > > On Fri, Mar 27, 2020 at 10:35:34AM +0100, Arnaud POULIQUEN wrote: > >> Hi > >> > >> On 3/26/20 11:01 PM, Mathieu Poirier wrote: > >>> On Thu, 26 Mar 2020 at 14:42, Suman Anna wrote: > >>>> > >>>> On 3/26/20 3:21 PM, Mathieu Poirier wrote: > >>>>> On Thu, 26 Mar 2020 at 09:06, Suman Anna wrote: > >>>>>> > >>>>>> Hi Mathieu, > >>>>>> > >>>>>> On 3/10/20 10:50 AM, Mathieu Poirier wrote: > >>>>>>> Adding the capability to supplement the base definition published > >>>>>>> by an rpmsg_driver with a postfix description so that it is possible > >>>>>>> for several entity to use the same service. > >>>>>>> > >>>>>>> Signed-off-by: Mathieu Poirier > >>>>>>> Acked-by: Arnaud Pouliquen > >>>>>> > >>>>>> So, the concern I have here is that we are retrofitting this into the > >>>>>> existing 32-byte name field, and the question is if it is going to be > >>>>>> enough in general. That's the reason I went with the additional 32-byte > >>>>>> field with the "rpmsg: add a description field" patch. > >>>>>> > >>>>> > >>>>> That's a valid concern. > >>>>> > >>>>> Did you consider increasing the size of RPMSG_NAME_SIZE to 64? Have > >>>>> you found cases where that wouldn't work? I did a survey of all the > >>>>> places the #define is used and all destination buffers are also using > >>>>> the same #define in their definition. It would also be backward > >>>>> compatible with firmware implementations that use 32 byte. > >>>> > >>>> You can't directly bump the size without breaking the compatibility on > >>>> the existing rpmsg_ns_msg in firmwares right? All the Linux-side drivers > >>>> will be ok since they use the same macro but rpmsg_ns_msg has presence > >>>> on both kernel and firmware-sides. > >>> > >>> Ah yes yes... The amount of bytes coming out of the pipe won't match. > >>> Let me think a little... > >> > >> +1 for Suman's concern. > >> > >> Anyway i would like to challenge the need of more than 32 bytes to > >> differentiate service instances. > >> "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA", seems to me enough if we only need > >> to differentiate the instances. > > Remember that the rpmsg_device_id name takes some space within here. So, > the shorter the rpmsg_device_id table name, the more room you have. > > >> > >> But perhaps the need is also to provide a short description of the service? > > I am mostly using it to provide a unique instantiation name. In anycase, > I have cross-checked against my current firmwares, and so far all of > them happen to have the name + desc < 31 bytes. > > > >> > >> Suman, could you share some examples of your need? > > > > Looking at things further it is possible to extend the name of the service to > > 64 byte while keeping backward compatibility by looking up the size of @len > > in function rpmsg_ns_cb(). From there work with an rpmsg_ns_msg or a new > > rpmsg_ns_msg64, pretty much the way you did in your patch[1]. In fact the > > approach is the same except you are using 2 arrays of 32 byte and I'm using one > > of 64. > > > > As Arnaud mentioned, is there an immediate need to support a 64-byte name? If > > not than I suggest to move forward with this patch and address the issue when we > > get there - at least we know there is room for extention. Otherwise I'll spin > > off another revision but it will be bigger and more complex. > > Yeah ok. I have managed to get my downstream drivers that use the desc > field working with this patch after modifying the firmwares to publish > using combined name, and adding logic in probe to get the trailing > portion of the name. Perfect > > So, the only thing that is missing or content for another patch is if we > need to add some tooling/helper stuff for giving the trailing stuff to > rpmsg drivers? So that all rpmsg drivers don't come up with their own parsing that ends up doing the same thing. Let me think about that - I may have to get back to you... > > regards > Suman > > > > > Thanks, > > Mathieu > > > > [1]. https://patchwork.kernel.org/patch/11096599/ > > > >>>>>> > >>>>>>> --- > >>>>>>> Changes for V2: > >>>>>>> - Added Arnaud's Acked-by. > >>>>>>> - Rebased to latest rproc-next. > >>>>>>> > >>>>>>> drivers/rpmsg/rpmsg_core.c | 20 +++++++++++++++++++- > >>>>>>> 1 file changed, 19 insertions(+), 1 deletion(-) > >>>>>>> > >>>>>>> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c > >>>>>>> index e330ec4dfc33..bfd25978fa35 100644 > >>>>>>> --- a/drivers/rpmsg/rpmsg_core.c > >>>>>>> +++ b/drivers/rpmsg/rpmsg_core.c > >>>>>>> @@ -399,7 +399,25 @@ ATTRIBUTE_GROUPS(rpmsg_dev); > >>>>>>> static inline int rpmsg_id_match(const struct rpmsg_device *rpdev, > >>>>>>> const struct rpmsg_device_id *id) > >>>>>>> { > >>>>>>> - return strncmp(id->name, rpdev->id.name, RPMSG_NAME_SIZE) == 0; > >>>>>>> + size_t len = min_t(size_t, strlen(id->name), RPMSG_NAME_SIZE); > >>>>>>> + > >>>>>>> + /* > >>>>>>> + * Allow for wildcard matches. For example if rpmsg_driver::id_table > >>>>>>> + * is: > >>>>>>> + * > >>>>>>> + * static struct rpmsg_device_id rpmsg_driver_sample_id_table[] = { > >>>>>>> + * { .name = "rpmsg-client-sample" }, > >>>>>>> + * { }, > >>>>>>> + * } > >>>>>>> + * > >>>>>>> + * Then it is possible to support "rpmsg-client-sample*", i.e: > >>>>>>> + * rpmsg-client-sample > >>>>>>> + * rpmsg-client-sample_instance0 > >>>>>>> + * rpmsg-client-sample_instance1 > >>>>>>> + * ... > >>>>>>> + * rpmsg-client-sample_instanceX > >>>>>>> + */ > >>>>>>> + return strncmp(id->name, rpdev->id.name, len) == 0; > >>>>>>> } > >>>>>>> > >>>>>>> /* match rpmsg channel and rpmsg driver */ > >>>>>>> > >>>>>> > >>>> >