linux-kernel - Re: [PATCH v2] rpmsg: core: Add wildcard match for name service

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Date:   Thu, 26 Mar 2020 16:01:28 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suman Anna <s-anna@...com>
Cc:     Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-remoteproc <linux-remoteproc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] rpmsg: core: Add wildcard match for name service

On Thu, 26 Mar 2020 at 14:42, Suman Anna <s-anna@...com> wrote:
>
> On 3/26/20 3:21 PM, Mathieu Poirier wrote:
> > On Thu, 26 Mar 2020 at 09:06, Suman Anna <s-anna@...com> 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 <mathieu.poirier@...aro.org>
> >>> Acked-by: Arnaud Pouliquen <arnaud.pouliquen@...com>
> >>
> >> 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...

>
> regards
> Suman
>
> >
> > Thanks,
> > Mathieu
> >
> >> regards
> >> Suman
> >>
> >>> ---
> >>> 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 */
> >>>
> >>
>