diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst
index 29072c166d236a25e175df3f1677b607a4449013..8cd62c466d20aac597fa5aa15ecfb2930c15c252 100644
--- a/Documentation/usb/gadget-testing.rst
+++ b/Documentation/usb/gadget-testing.rst
@@ -448,15 +448,17 @@ Function-specific configfs interface
The function name to use when creating the function directory is "ncm".
The NCM function provides these attributes in its function directory:
- =============== ==================================================
- ifname network device interface name associated with this
- function instance
- qmult queue length multiplier for high and super speed
- host_addr MAC address of host's end of this
- Ethernet over USB link
- dev_addr MAC address of device's end of this
- Ethernet over USB link
- =============== ==================================================
+ =============== ==================================================
+ ifname network device interface name associated with this
+ function instance
+ qmult queue length multiplier for high and super speed
+ host_addr MAC address of host's end of this
+ Ethernet over USB link
+ dev_addr MAC address of device's end of this
+ Ethernet over USB link
+ max_segment_size Segment size required for P2P connections. This
+ will set MTU to (max_segment_size - 14 bytes)
+ =============== ==================================================
and after creating the functions/ncm.<instance name> they contain default
values: qmult is 5, dev_addr and host_addr are randomly selected.
diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c
index cc0ed29a4adc07b62fa412802c2b42495e5c22d8..a1575a0ca568d7c46bc23bd605404096db14e6e5 100644
--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -103,6 +103,16 @@ static inline struct f_ncm *func_to_ncm(struct usb_function *f)
/* Delay for the transmit to wait before sending an unfilled NTB frame. */
#define TX_TIMEOUT_NSECS 300000
+/*
+ * Although max mtu as dictated by u_ether is 15412 bytes, setting
+ * max_segment_sizeto 15426 would not be efficient. If user chooses segment
+ * size to be (>= 8192), then we can't aggregate more than one buffer in each
+ * NTB (assuming each packet coming from network layer is >= 8192 bytes) as ep
+ * maxpacket limit is 16384. So let max_segment_size be limited to 8000 to allow
+ * at least 2 packets to be aggregated reducing wastage of NTB buffer space
+ */
+#define MAX_DATAGRAM_SIZE 8000
+
#define FORMATS_SUPPORTED (USB_CDC_NCM_NTB16_SUPPORTED | \
USB_CDC_NCM_NTB32_SUPPORTED)
@@ -179,7 +189,6 @@ static struct usb_cdc_ether_desc ecm_desc = {
/* this descriptor actually adds value, surprise! */
/* .iMACAddress = DYNAMIC */
.bmEthernetStatistics = cpu_to_le32(0), /* no statistics */
- .wMaxSegmentSize = cpu_to_le16(ETH_FRAME_LEN),
.wNumberMCFilters = cpu_to_le16(0),
.bNumberPowerFilters = 0,
};
@@ -1166,11 +1175,15 @@ static int ncm_unwrap_ntb(struct gether *port,
struct sk_buff *skb2;
int ret = -EINVAL;
unsigned ntb_max = le32_to_cpu(ntb_parameters.dwNtbOutMaxSize);
- unsigned frame_max = le16_to_cpu(ecm_desc.wMaxSegmentSize);
+ unsigned frame_max;
const struct ndp_parser_opts *opts = ncm->parser_opts;
unsigned crc_len = ncm->is_crc ? sizeof(uint32_t) : 0;
int dgram_counter;
int to_process = skb->len;
+ struct f_ncm_opts *ncm_opts;
+
+ ncm_opts = container_of(port->func.fi, struct f_ncm_opts, func_inst);
+ frame_max = ncm_opts->max_segment_size;
parse_ntb:
tmp = (__le16 *)ntb_ptr;
@@ -1430,8 +1443,10 @@ static int ncm_bind(struct usb_configuration *c, struct usb_function *f)
mutex_lock(&ncm_opts->lock);
gether_set_gadget(ncm_opts->net, cdev->gadget);
- if (!ncm_opts->bound)
+ if (!ncm_opts->bound) {
+ ncm_opts->net->mtu = (ncm_opts->max_segment_size - ETH_HLEN);
status = gether_register_netdev(ncm_opts->net);
+ }
mutex_unlock(&ncm_opts->lock);
if (status)
@@ -1474,6 +1489,8 @@ static int ncm_bind(struct usb_configuration *c, struct usb_function *f)
ncm_data_intf.bInterfaceNumber = status;
ncm_union_desc.bSlaveInterface0 = status;
+ ecm_desc.wMaxSegmentSize = ncm_opts->max_segment_size;
+
status = -ENODEV;
/* allocate instance-specific endpoints */
@@ -1576,11 +1593,56 @@ USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(ncm);
/* f_ncm_opts_ifname */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(ncm);
+static ssize_t ncm_opts_max_segment_size_show(struct config_item *item,
+ char *page)
+{
+ struct f_ncm_opts *opts = to_f_ncm_opts(item);
+ u16 segment_size;
+
+ mutex_lock(&opts->lock);
+ segment_size = opts->max_segment_size;
+ mutex_unlock(&opts->lock);
+
+ return sysfs_emit(page, "%u\n", segment_size);
+}
+
+static ssize_t ncm_opts_max_segment_size_store(struct config_item *item,
+ const char *page, size_t len)
+{
+ struct f_ncm_opts *opts = to_f_ncm_opts(item);
+ u16 segment_size;
+ int ret;
+
+ mutex_lock(&opts->lock);
+ if (opts->refcnt) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ ret = kstrtou16(page, 0, &segment_size);
+ if (ret)
+ goto out;
+
+ if (segment_size > MAX_DATAGRAM_SIZE) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ opts->max_segment_size = segment_size;
+ ret = len;
+out:
+ mutex_unlock(&opts->lock);
+ return ret;
+}
+
+CONFIGFS_ATTR(ncm_opts_, max_segment_size);
+
static struct configfs_attribute *ncm_attrs[] = {
&ncm_opts_attr_dev_addr,
&ncm_opts_attr_host_addr,
&ncm_opts_attr_qmult,
&ncm_opts_attr_ifname,
+ &ncm_opts_attr_max_segment_size,
NULL,
};
@@ -1623,6 +1685,7 @@ static struct usb_function_instance *ncm_alloc_inst(void)
kfree(opts);
return ERR_CAST(net);
}
+ opts->max_segment_size = cpu_to_le16(ETH_FRAME_LEN);
INIT_LIST_HEAD(&opts->ncm_os_desc.ext_prop);
descs[0] = &opts->ncm_os_desc;
diff --git a/drivers/usb/gadget/function/u_ncm.h b/drivers/usb/gadget/function/u_ncm.h
index 5408854d84072dc7e35646ee978fb09cdeaa7f19..49ec095cdb4b6dcb330fd3149b502840312f78ec 100644
--- a/drivers/usb/gadget/function/u_ncm.h
+++ b/drivers/usb/gadget/function/u_ncm.h
@@ -31,6 +31,8 @@ struct f_ncm_opts {
*/
struct mutex lock;
int refcnt;
+
+ u16 max_segment_size;
};
#endif /* U_NCM_H */