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SubjectRe: [PATCH v7 1/2] rpmsg: core: add API to get MTU
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On 24. 03. 20, 18:04, 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>
> Acked-by: Suman Anna <s-anna@ti.com>
> ---
> 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;

Hmm, I don't think all callers of tty_write_room() handle negative values...

But some drivers also return negative values. There is some work to be
done, adding to TODO.

For the time being, I suggest returning 0 instead.

thanks,
--
js
suse labs

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