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SubjectRe: [PATCH v2] rpmsg: core: add API to get MTU
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Hi Suman,

On 1/15/20 12:40 AM, Suman Anna wrote:
> Hi Arnaud,
>
> On 1/13/20 7:19 AM, Arnaud POULIQUEN wrote:
>> Hi Bjorn, Suman,
>>
>> Gentleman reminder :)
>
> Thanks for the revised version, and very sorry about the delay. Only
> one minor nit that you missed from my comments the v6 rpmsg-tty series
> [1], otherwise I am good with the changes. See below.
>
> FWIW, I have already been using this patch on our downstream 2020 LTS
> based kernel and eliminate the the need to expose the virtio_rpmsg's
> rpmsg_hdr to rpmsg client drivers :).
Right without this API the client needs also to know the RPMSG buffer size to
compute the MTU.
>
>>
>> Thank in advance,
>>
>> Arnaud
>>
>> On 11/13/19 6:22 PM, Arnaud Pouliquen wrote:
>>> Return the rpmsg buffer MTU for sending message, so rpmsg users
>>> can split a long message in several sub rpmsg buffers.
>>>
>>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
>>> ---
>>> V1 to V2
>>>
>>> V1 patch:https://lore.kernel.org/patchwork/patch/1124684/
>>> - Change patch title,
>>> - as not solution today to support MTU on GLINK make ops optional,
>>> RPMsg client API returns -ENOTSUPP in this case,
>>> - suppress smd and glink patches.
>>> ---
>>> 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 e330ec4dfc33..a6ef54c4779a 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_mtu)
>>> + return -ENOTSUPP;
>>> +
>>> + return ept->ops->get_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 3fc83cd50e98..0e56e046f5c6 100644
>>> --- a/drivers/rpmsg/rpmsg_internal.h
>>> +++ b/drivers/rpmsg/rpmsg_internal.h
>>> @@ -47,6 +47,7 @@ struct rpmsg_device_ops {
>>> * @trysendto: see @rpmsg_trysendto(), optional
>>> * @trysend_offchannel: see @rpmsg_trysend_offchannel(), optional
>>> * @poll: see @rpmsg_poll(), optional
>>> + * @get_mtu: see @get_mpu(), optional
>
> In the description for the ops, 'mpu' is a typo. My earlier comment was
> essentially,
> %s/see @get_mpu()/see @rpmsg_get_mtu()/
Sorry, completly missed it i sent a v3

Thanks,
Arnaud

>
> regards
> Suman
>
> [1] https://patchwork.kernel.org/patch/11130209/
>
>>> *
>>> * Indirection table for the operations that a rpmsg backend should implement.
>>> * In addition to @destroy_ept, the backend must at least implement @send and
>>> @@ -66,6 +67,7 @@ struct rpmsg_endpoint_ops {
>>> void *data, int len);
>>> __poll_t (*poll)(struct rpmsg_endpoint *ept, struct file *filp,
>>> poll_table *wait);
>>> + ssize_t (*get_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 376ebbf880d6..6e48fdf24555 100644
>>> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
>>> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
>>> @@ -175,6 +175,7 @@ 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_rpmsg_get_mtu(struct rpmsg_endpoint *ept);
>>>
>>> static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
>>> .destroy_ept = virtio_rpmsg_destroy_ept,
>>> @@ -184,6 +185,7 @@ static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
>>> .trysend = virtio_rpmsg_trysend,
>>> .trysendto = virtio_rpmsg_trysendto,
>>> .trysend_offchannel = virtio_rpmsg_trysend_offchannel,
>>> + .get_mtu = virtio_rpmsg_get_mtu,
>>> };
>>>
>>> /**
>>> @@ -699,6 +701,14 @@ 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_rpmsg_get_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..88d7892ca93d 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 inline 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 */
>>>
>

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