rpmsg: core: add API to get MTU

Return the rpmsg buffer MTU for sending message, so rpmsg users
can split a long message in several sub rpmsg buffers.

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20211015094701.5732-2-arnaud.pouliquen@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
index 9151836190ce39f17b4e060a2092e7aa80669708..d3eb60059ef16c39dcd083007e62cc9384827ec4 100644 (file)
--- a/drivers/rpmsg/rpmsg_core.c
+++ b/drivers/rpmsg/rpmsg_core.c
@@ -327,6 +327,27 @@ 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 outgoing 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 a 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 a76c344253bf58d2f3c9c5e99277ef55e3f1f4f3..b1245d3ed7c668b90e17e2b857a729286d9ca07d 100644 (file)
--- a/drivers/rpmsg/rpmsg_internal.h
+++ b/drivers/rpmsg/rpmsg_internal.h
@@ -53,6 +53,7 @@ struct rpmsg_device_ops {
  * @trysendto:         see @rpmsg_trysendto(), optional
  * @trysend_offchannel:        see @rpmsg_trysend_offchannel(), optional
  * @poll:              see @rpmsg_poll(), optional
+ * @get_mtu:           see @rpmsg_get_mtu(), optional
  *
  * Indirection table for the operations that a rpmsg backend should implement.
  * In addition to @destroy_ept, the backend must at least implement @send and
@@ -72,6 +73,7 @@ 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);
 };
 
 struct device *rpmsg_find_device(struct device *parent,

diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 8e49a3bacfc784ae6e058d36eb6acf188cc702aa..05fd06fc67e918c320bb51d17b5ce5d71f5ea8a4 100644 (file)
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -149,6 +149,7 @@ 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 struct rpmsg_device *__rpmsg_create_channel(struct virtproc_info *vrp,
                                                   struct rpmsg_channel_info *chinfo);
 
@@ -160,6 +161,7 @@ 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,
 };
 
 /**
@@ -696,6 +698,14 @@ 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 d97dcd049f18f8630c52a00c8856bbf822a72ca6..990b80fb49ad1b84f783e764ccf411c151afcbb5 100644 (file)
--- a/include/linux/rpmsg.h
+++ b/include/linux/rpmsg.h
@@ -186,6 +186,8 @@ 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 rpmsg_register_device(struct rpmsg_device *rpdev)
@@ -296,6 +298,14 @@ 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 */