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

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Date:   Thu, 26 Mar 2020 15:42:44 -0500
From:   Suman Anna <s-anna@...com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
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 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.

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 */
>>>
>>