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Subject: Re: [PATCH v5 1/2] rpmsg: core: add API to get message length
To:     Arnaud Pouliquen <arnaud.pouliquen@st.com>,
        Ohad Ben-Cohen <ohad@wizery.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>,
        xiang xiao <xiaoxiang781216@gmail.com>,
        <linux-kernel@vger.kernel.org>, <linux-remoteproc@vger.kernel.org>
CC:     Fabien DESSENNE <fabien.dessenne@st.com>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        Alan Cox <gnomes@lxorguk.ukuu.org.uk>
References: <1567005566-10986-1-git-send-email-arnaud.pouliquen@st.com>
 <1567005566-10986-2-git-send-email-arnaud.pouliquen@st.com>
 <7dc4d1cf-4f15-19ab-b8dd-424175f2a11a@ti.com>
 <f6f2ad3e-123a-268b-2586-544752c54db7@st.com>
From:   Suman Anna <s-anna@ti.com>
Message-ID: <2a81a04d-e4f9-b9c8-57ec-47f8e140235a@ti.com>
Date:   Tue, 3 Sep 2019 11:06:06 -0500
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Hi Arnaud,

On 9/3/19 4:49 AM, Arnaud Pouliquen wrote:
> hi Suman
> 
> On 8/29/19 12:34 AM, Suman Anna wrote:
>> Hi Arnaud,
>>
>> On 8/28/19 10:19 AM, Arnaud Pouliquen wrote:
>>> Return the rpmsg buffer size for sending message, so rpmsg users
>>> can split a long message in several sub rpmsg buffers.
>>
>> Thanks for the patch, I also have a need for the same to be able to
>> compute permissible payload size. Minor comments below.
> 
> Thanks for your review. i will update it ASAP. Then if you need it and
> ack it, i suppose that we could request Bjorn to integrate it in a first
> step, if the rpmsg tty driver has not a level of quality sufficient to
> be accepted...

Yeah, this patch can always be merged independently ahead of the rpmsg
tty driver. Anyways, the tty patch will have to be picked up by a
separate maintainer right. So, it would be nice to get the revised
version get into 5.4

regards
Suman

> 
> Regards
> Arnaud
>>
>>>
>>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
>>> ---
>>> V4 to V5 :
>>>    - rename rpmsg_get_buf_payload_size to rpmsg_get_mtu
>>>
>>>   drivers/rpmsg/rpmsg_core.c       | 21 +++++++++++++++++++++
>>>   drivers/rpmsg/rpmsg_internal.h   |  2 ++
>>>   drivers/rpmsg/virtio_rpmsg_bus.c | 10 ++++++++++
>>>   include/linux/rpmsg.h            | 10 ++++++++++
>>>   4 files changed, 43 insertions(+)
>>>
>>> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
>>> index 8122807db380..daca2e24fc71 100644
>>> --- a/drivers/rpmsg/rpmsg_core.c
>>> +++ b/drivers/rpmsg/rpmsg_core.c
>>> @@ -283,6 +283,27 @@ int rpmsg_trysend_offchannel(struct
>>> rpmsg_endpoint *ept, u32 src, u32 dst,
>>>   }
>>>   EXPORT_SYMBOL(rpmsg_trysend_offchannel);
>>>   +/**
>>> + * rpmsg_get_mtu() - get maximum transmission buffer size for
>>> sending message.
>>> + * @ept: the rpmsg endpoint
>>> + *
>>> + * This function returns maximum buffer size available for a single
>>> message.
>>> + *
>>> + * Return: the maximum transmission size on success and an
>>> appropriate error
>>> + * value on failure.
>>> + */
>>> +
>>> +ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept)
>>> +{
>>> +    if (WARN_ON(!ept))
>>> +        return -EINVAL;
>>> +    if (!ept->ops->get_buf_mtu)
>>
>> How about calling the ops just get_mtu or rename the function to follow
>> the ops name, like all the others.
>>
>>> +        return -ENXIO;
>>
>> Perhaps ENOTSUPP or EOPNOTSUPP.
>>
>>> +
>>> +    return ept->ops->get_buf_mtu(ept);
>>> +}
>>> +EXPORT_SYMBOL(rpmsg_get_mtu);
>>> +
>>>   /*
>>>    * match an rpmsg channel with a channel info struct.
>>>    * this is used to make sure we're not creating rpmsg devices for
>>> channels
>>> diff --git a/drivers/rpmsg/rpmsg_internal.h
>>> b/drivers/rpmsg/rpmsg_internal.h
>>> index 0d791c30b7ea..645c402569ac 100644
>>> --- a/drivers/rpmsg/rpmsg_internal.h
>>> +++ b/drivers/rpmsg/rpmsg_internal.h
>>> @@ -46,6 +46,7 @@ struct rpmsg_device_ops {
>>>    * @trysend:        see @rpmsg_trysend(), required
>>>    * @trysendto:        see @rpmsg_trysendto(), optional
>>>    * @trysend_offchannel:    see @rpmsg_trysend_offchannel(), optional
>>> + * @get_buf_payload_size: see @rpmsg_get_buf_payload_size(), optional
>>
>> Missed updating the kerneldoc to the new name.
>>
>>>    *
>>>    * Indirection table for the operations that a rpmsg backend should
>>> implement.
>>>    * In addition to @destroy_ept, the backend must at least implement
>>> @send and
>>> @@ -65,6 +66,7 @@ struct rpmsg_endpoint_ops {
>>>                    void *data, int len);
>>>       __poll_t (*poll)(struct rpmsg_endpoint *ept, struct file *filp,
>>>                    poll_table *wait);
>>> +    ssize_t (*get_buf_mtu)(struct rpmsg_endpoint *ept);
>>>   };
>>>     int rpmsg_register_device(struct rpmsg_device *rpdev);
>>> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c
>>> b/drivers/rpmsg/virtio_rpmsg_bus.c
>>> index e757f0038a1c..f80b1ad23e7e 100644
>>> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
>>> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
>>> @@ -178,6 +178,7 @@ static int virtio_rpmsg_trysendto(struct
>>> rpmsg_endpoint *ept, void *data,
>>>                     int len, u32 dst);
>>>   static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint
>>> *ept, u32 src,
>>>                          u32 dst, void *data, int len);
>>> +static ssize_t virtio_get_buf_mtu(struct rpmsg_endpoint *ept);
>>
>> Minor nit, virtio_rpmsg_ prefix similar to all the other ops.
>>
>> regards
>> Suman
>>
>>>     static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
>>>       .destroy_ept = virtio_rpmsg_destroy_ept,
>>> @@ -187,6 +188,7 @@ static const struct rpmsg_endpoint_ops
>>> virtio_endpoint_ops = {
>>>       .trysend = virtio_rpmsg_trysend,
>>>       .trysendto = virtio_rpmsg_trysendto,
>>>       .trysend_offchannel = virtio_rpmsg_trysend_offchannel,
>>> +    .get_buf_mtu = virtio_get_buf_mtu,
>>>   };
>>>     /**
>>> @@ -702,6 +704,14 @@ static int
>>> virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
>>>       return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len,
>>> false);
>>>   }
>>>   +static ssize_t virtio_get_buf_mtu(struct rpmsg_endpoint *ept)
>>> +{
>>> +    struct rpmsg_device *rpdev = ept->rpdev;
>>> +    struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
>>> +
>>> +    return vch->vrp->buf_size - sizeof(struct rpmsg_hdr);
>>> +}
>>> +
>>>   static int rpmsg_recv_single(struct virtproc_info *vrp, struct
>>> device *dev,
>>>                    struct rpmsg_hdr *msg, unsigned int len)
>>>   {
>>> diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
>>> index 9fe156d1c018..9d638bf2bdce 100644
>>> --- a/include/linux/rpmsg.h
>>> +++ b/include/linux/rpmsg.h
>>> @@ -135,6 +135,8 @@ int rpmsg_trysend_offchannel(struct
>>> rpmsg_endpoint *ept, u32 src, u32 dst,
>>>   __poll_t rpmsg_poll(struct rpmsg_endpoint *ept, struct file *filp,
>>>               poll_table *wait);
>>>   +ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept);
>>> +
>>>   #else
>>>     static inline int register_rpmsg_device(struct rpmsg_device *dev)
>>> @@ -242,6 +244,14 @@ static inline __poll_t rpmsg_poll(struct
>>> rpmsg_endpoint *ept,
>>>       return 0;
>>>   }
>>>   +static ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept)
>>> +{
>>> +    /* This shouldn't be possible */
>>> +    WARN_ON(1);
>>> +
>>> +    return -ENXIO;
>>> +}
>>> +
>>>   #endif /* IS_ENABLED(CONFIG_RPMSG) */
>>>     /* use a macro to avoid include chaining to get THIS_MODULE */
>>>
>>