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SubjectRe: [PATCH v3 2/3] net/usb/r8152: replace USB buffer from stack to DMA-able
On Tue, Jul 30, 2013 at 04:28:55PM +0800, Hayes Wang wrote:
> Allocate the required transfer buffer for usb_control_msg.
>
> Signed-off-by: Hayes Wang <hayeswang@realtek.com>
> ---
> drivers/net/usb/r8152.c | 91 +++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 66 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index ee13f9e..93a7baa 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -282,6 +282,8 @@ enum rtl_register_content {
> #define RTL8152_RMS (VLAN_ETH_FRAME_LEN + VLAN_HLEN)
> #define RTL8152_TX_TIMEOUT (HZ)
>
> +#define RTL8152_MAX_TRANSFER_SIZE 8
> +
> /* rtl8152 flags */
> enum rtl8152_flags {
> RTL8152_UNPLUG = 0,
> @@ -324,8 +326,10 @@ struct r8152 {
> struct sk_buff *tx_skb, *rx_skb;
> struct delayed_work schedule;
> struct mii_if_info mii;
> + struct mutex transfer_mutex;
> u32 msg_enable;
> u16 ocp_base;
> + u8 *transfer_buf;
> u8 version;
> u8 speed;
> };
> @@ -344,17 +348,59 @@ static const int multicast_filter_limit = 32;
> static
> int get_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
> {
> - return usb_control_msg(tp->udev, usb_rcvctrlpipe(tp->udev, 0),
> + int ret;
> + void *tmp;
> +
> + if (size > RTL8152_MAX_TRANSFER_SIZE || !tp->transfer_buf) {
> + tmp = kmalloc(size, GFP_KERNEL);
> + if (!tmp)
> + return -ENOMEM;
> + } else {
> + mutex_lock(&tp->transfer_mutex);
> + tmp = tp->transfer_buf;
> + }
> +
> + ret = usb_control_msg(tp->udev, usb_rcvctrlpipe(tp->udev, 0),
> RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
> - value, index, data, size, 500);
> + value, index, tmp, size, 500);

Same here, no need for your "transfer buf" structure, just always
kmalloc the data, copy it in, and make the call. It's _really_ slow
anyway, you will never notice any speed overhead by doing this.

thanks,

greg k-h


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