net: cdc_ncm: use true max dgram count for header estimates
Many newer NCM and MBIM devices will request a maximum tx
datagram count which is much smaller than our hard-coded
absolute max. We can reduce the overhead without sacrificing
any of the simplicity for these devices, by simply using the
true negotiated count in when calculated the maximum NTH and
NDP header sizes.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 141dbec..b9b562b 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -174,7 +174,7 @@
}
/* clamp new_tx to sane values */
- min = CDC_NCM_MIN_HDR_SIZE + ctx->max_datagram_size;
+ min = ctx->max_datagram_size + ctx->max_ndp_size + sizeof(struct usb_cdc_ncm_nth16);
max = min_t(u32, CDC_NCM_NTB_MAX_SIZE_TX, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));
/* some devices set dwNtbOutMaxSize too low for the above default */
@@ -318,6 +318,9 @@
(ctx->tx_max_datagrams > CDC_NCM_DPT_DATAGRAMS_MAX))
ctx->tx_max_datagrams = CDC_NCM_DPT_DATAGRAMS_MAX;
+ /* set up maximum NDP size */
+ ctx->max_ndp_size = sizeof(struct usb_cdc_ncm_ndp16) + (ctx->tx_max_datagrams + 1) * sizeof(struct usb_cdc_ncm_dpe16);
+
/* initial coalescing timer interval */
ctx->timer_interval = CDC_NCM_TIMER_INTERVAL_USEC * NSEC_PER_USEC;
@@ -800,7 +803,7 @@
cdc_ncm_align_tail(skb, ctx->tx_ndp_modulus, 0, ctx->tx_max);
/* verify that there is room for the NDP and the datagram (reserve) */
- if ((ctx->tx_max - skb->len - reserve) < CDC_NCM_NDP_SIZE)
+ if ((ctx->tx_max - skb->len - reserve) < ctx->max_ndp_size)
return NULL;
/* link to it */
@@ -810,7 +813,7 @@
nth16->wNdpIndex = cpu_to_le16(skb->len);
/* push a new empty NDP */
- ndp16 = (struct usb_cdc_ncm_ndp16 *)memset(skb_put(skb, CDC_NCM_NDP_SIZE), 0, CDC_NCM_NDP_SIZE);
+ ndp16 = (struct usb_cdc_ncm_ndp16 *)memset(skb_put(skb, ctx->max_ndp_size), 0, ctx->max_ndp_size);
ndp16->dwSignature = sign;
ndp16->wLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_ndp16) + sizeof(struct usb_cdc_ncm_dpe16));
return ndp16;