Re: [Qemu-devel] [PATCH 12/18] usb-linux: split large xfers

[David Ahern <daahern@cisco.com>]

On 05/16/11 13:56, Gerd Hoffmann wrote:
> Add support for splitting large transfers into multiple smaller ones.
> This is needed for the upcoming EHCI emulation which allows guests
> to submit requests up to 20k in size.  The linux kernel allows 16k
> max size though.
> 
> Roughly based on a patch from git://git.kiszka.org/qemu.git ehci

More specifically:
http://www.mail-archive.com/qemu-devel@nongnu.org/msg30337.html

And "roughly based" is a bit of a stretch. The logic for handling 20k
requests in a 16k limit (the focus of this patch) came from the patch
above. This patch is a forward port based on changes made to the USB
code and some code movement.

David


> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  usb-linux.c |   68 +++++++++++++++++++++++++++++++++++++---------------------
>  1 files changed, 43 insertions(+), 25 deletions(-)
> 
> diff --git a/usb-linux.c b/usb-linux.c
> index b8f7705..b95c119 100644
> --- a/usb-linux.c
> +++ b/usb-linux.c
> @@ -89,6 +89,9 @@ static int usb_fs_type;
>  #define ISO_URB_COUNT 3
>  #define INVALID_EP_TYPE 255
>  
> +/* devio.c limits single requests to 16k */
> +#define MAX_USBFS_BUFFER_SIZE 16384
> +
>  typedef struct AsyncURB AsyncURB;
>  
>  struct endp_data {
> @@ -229,6 +232,7 @@ struct AsyncURB
>  
>      /* For regular async urbs */
>      USBPacket     *packet;
> +    int more; /* large transfer, more urbs follow */
>  
>      /* For buffered iso handling */
>      int iso_frame_idx; /* -1 means in flight */
> @@ -291,7 +295,7 @@ static void async_complete(void *opaque)
>          if (p) {
>              switch (aurb->urb.status) {
>              case 0:
> -                p->len = aurb->urb.actual_length;
> +                p->len += aurb->urb.actual_length;
>                  break;
>  
>              case -EPIPE:
> @@ -306,7 +310,7 @@ static void async_complete(void *opaque)
>  
>              if (aurb->urb.type == USBDEVFS_URB_TYPE_CONTROL) {
>                  usb_generic_async_ctrl_complete(&s->dev, p);
> -            } else {
> +            } else if (!aurb->more) {
>                  usb_packet_complete(&s->dev, p);
>              }
>          }
> @@ -646,7 +650,8 @@ static int usb_host_handle_data(USBDevice *dev, USBPacket *p)
>      USBHostDevice *s = DO_UPCAST(USBHostDevice, dev, dev);
>      struct usbdevfs_urb *urb;
>      AsyncURB *aurb;
> -    int ret;
> +    int ret, rem;
> +    uint8_t *pbuf;
>      uint8_t ep;
>  
>      if (!is_valid(s, p->devep)) {
> @@ -673,32 +678,45 @@ static int usb_host_handle_data(USBDevice *dev, USBPacket *p)
>          return usb_host_handle_iso_data(s, p, p->pid == USB_TOKEN_IN);
>      }
>  
> -    aurb = async_alloc(s);
> -    aurb->packet = p;
> +    rem = p->len;
> +    pbuf = p->data;
> +    p->len = 0;
> +    while (rem) {
> +        aurb = async_alloc(s);
> +        aurb->packet = p;
>  
> -    urb = &aurb->urb;
> +        urb = &aurb->urb;
> +        urb->endpoint      = ep;
> +        urb->type          = USBDEVFS_URB_TYPE_BULK;
> +        urb->usercontext   = s;
> +        urb->buffer        = pbuf;
>  
> -    urb->endpoint      = ep;
> -    urb->buffer        = p->data;
> -    urb->buffer_length = p->len;
> -    urb->type          = USBDEVFS_URB_TYPE_BULK;
> -    urb->usercontext   = s;
> +        if (rem > MAX_USBFS_BUFFER_SIZE) {
> +            urb->buffer_length = MAX_USBFS_BUFFER_SIZE;
> +            aurb->more         = 1;
> +        } else {
> +            urb->buffer_length = rem;
> +            aurb->more         = 0;
> +        }
> +        pbuf += urb->buffer_length;
> +        rem  -= urb->buffer_length;
>  
> -    ret = ioctl(s->fd, USBDEVFS_SUBMITURB, urb);
> +        ret = ioctl(s->fd, USBDEVFS_SUBMITURB, urb);
>  
> -    DPRINTF("husb: data submit. ep 0x%x len %u aurb %p\n",
> -            urb->endpoint, p->len, aurb);
> +        DPRINTF("husb: data submit: ep 0x%x, len %u, more %d, packet %p, aurb %p\n",
> +                urb->endpoint, urb->buffer_length, aurb->more, p, aurb);
>  
> -    if (ret < 0) {
> -        DPRINTF("husb: submit failed. errno %d\n", errno);
> -        async_free(aurb);
> +        if (ret < 0) {
> +            DPRINTF("husb: submit failed. errno %d\n", errno);
> +            async_free(aurb);
>  
> -        switch(errno) {
> -        case ETIMEDOUT:
> -            return USB_RET_NAK;
> -        case EPIPE:
> -        default:
> -            return USB_RET_STALL;
> +            switch(errno) {
> +            case ETIMEDOUT:
> +                return USB_RET_NAK;
> +            case EPIPE:
> +            default:
> +                return USB_RET_STALL;
> +            }
>          }
>      }
>