usb: gadget: u_ether: add a flag to avoid skb_reserve() calling

This patch adds a flag "no_skb_reserve" in struct eth_dev.
So, if a peripheral driver sets the quirk_avoids_skb_reserve flag,
upper network gadget drivers (e.g. f_ncm.c) can avoid skb_reserve()
calling using the flag as well.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

2 files changed, 5 insertions, 1 deletions

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 5f562c1ec795..3be4b93fd415 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -82,6 +82,7 @@ struct eth_dev {
 #define WORK_RX_MEMORY          0
 
         bool                    zlp;
+        bool                    no_skb_reserve;
         u8                      host_mac[ETH_ALEN];
         u8                      dev_mac[ETH_ALEN];
 };
@@ -233,7 +234,8 @@ rx_submit(struct eth_dev *dev, struct usb_request *req, gfp_t gfp_flags)
          * but on at least one, checksumming fails otherwise.  Note:
          * RNDIS headers involve variable numbers of LE32 values.
          */
-        skb_reserve(skb, NET_IP_ALIGN);
+        if (likely(!dev->no_skb_reserve))
+                skb_reserve(skb, NET_IP_ALIGN);
 
         req->buf = skb->data;
         req->length = size;
@@ -1063,6 +1065,7 @@ struct net_device *gether_connect(struct gether *link)
 
         if (result == 0) {
                 dev->zlp = link->is_zlp_ok;
+                dev->no_skb_reserve = link->no_skb_reserve;
                 DBG(dev, "qlen %d\n", qlen(dev->gadget, dev->qmult));
 
                 dev->header_len = link->header_len;
diff --git a/drivers/usb/gadget/function/u_ether.h b/drivers/usb/gadget/function/u_ether.h
index c77145bd6b5b..81d94a7ae4b4 100644
--- a/drivers/usb/gadget/function/u_ether.h
+++ b/drivers/usb/gadget/function/u_ether.h
@@ -64,6 +64,7 @@ struct gether {
         struct usb_ep                   *out_ep;
 
         bool                            is_zlp_ok;
+        bool                            no_skb_reserve;
 
         u16                             cdc_filter;