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SubjectRe: [PATCH v2] rpmsg: core: add API to get MTU
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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 :).

>
> 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()/

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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