Re: [PATCH v4 1/4] usb: gadget: Support already-mapped DMA SGs

Frank Li
2024-01-19T21:49:17Z

On Wed, Jan 17, 2024 at 01:26:43PM +0100, Paul Cercueil wrote:
> Add a new 'sg_was_mapped' field to the struct usb_request. This field
> can be used to indicate that the scatterlist associated to the USB
> transfer has already been mapped into the DMA space, and it does not
> have to be done internally.
>
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
> drivers/usb/gadget/udc/core.c | 7 ++++++-
> include/linux/usb/gadget.h | 2 ++
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index d59f94464b87..9d4150124fdb 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -903,6 +903,11 @@ int usb_gadget_map_request_by_dev(struct device *dev,
> if (req->length == 0)
> return 0;
>
> + if (req->sg_was_mapped) {
> + req->num_mapped_sgs = req->num_sgs;
> + return 0;
> + }
> +
> if (req->num_sgs) {
> int mapped;
>
> @@ -948,7 +953,7 @@ EXPORT_SYMBOL_GPL(usb_gadget_map_request);
> void usb_gadget_unmap_request_by_dev(struct device *dev,
> struct usb_request *req, int is_in)
> {
> - if (req->length == 0)
> + if (req->length == 0 || req->sg_was_mapped)
> return;
>
> if (req->num_mapped_sgs) {
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index a771ccc038ac..c529e4e06997 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -52,6 +52,7 @@ struct usb_ep;
> * @short_not_ok: When reading data, makes short packets be
> * treated as errors (queue stops advancing till cleanup).
> * @dma_mapped: Indicates if request has been mapped to DMA (internal)
> + * @sg_was_mapped: Set if the scatterlist has been mapped before the request
> * @complete: Function called when request completes, so this request and
> * its buffer may be re-used. The function will always be called with
> * interrupts disabled, and it must not sleep.
> @@ -111,6 +112,7 @@ struct usb_request {
> unsigned zero:1;
> unsigned short_not_ok:1;
> unsigned dma_mapped:1;
> + unsigned sg_was_mapped:1;

why not use dma_mapped direclty?

Frank

>
> void (*complete)(struct usb_ep *ep,
> struct usb_request *req);
> --
> 2.43.0
>