LinuxLists.cc - [PATCH] usb: gadget: Support transfers from device memory

2023-10-31 03:54:41

Subject: [PATCH] usb: gadget: Support transfers from device memory

USB gadget stack only supports usb_request objects that point to buffers
located in memory. Support use cases where data is transferred from
physical addresses in device mmio regions

Added a bit "pre_mapped" to usb_request to bypass dma_map_single and
dma_map_sg for such requests

The caller must determine the dma address for the request before queuing
it

Signed-off-by: Manan Aurora <[email protected]>
---
drivers/usb/gadget/udc/core.c | 4 ++--
include/linux/usb/gadget.h | 1 +
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index ded9531f141b..236165ba08f4 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -900,7 +900,7 @@ EXPORT_SYMBOL_GPL(usb_gadget_activate);
int usb_gadget_map_request_by_dev(struct device *dev,
struct usb_request *req, int is_in)
{
- if (req->length == 0)
+ if (req->pre_mapped || req->length == 0)
return 0;

if (req->num_sgs) {
@@ -948,7 +948,7 @@ 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->pre_mapped || req->length == 0)
return;

if (req->num_mapped_sgs) {
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index a771ccc038ac..6bc035439098 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -111,6 +111,7 @@ struct usb_request {
unsigned zero:1;
unsigned short_not_ok:1;
unsigned dma_mapped:1;
+ unsigned pre_mapped:1;

void (*complete)(struct usb_ep *ep,
struct usb_request *req);
--
2.42.0.820.g83a721a137-goog

2023-10-31 06:17:30

by Greg Kroah-Hartman

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Subject: Re: [PATCH] usb: gadget: Support transfers from device memory

On Tue, Oct 31, 2023 at 03:54:02AM +0000, Manan Aurora wrote:
> USB gadget stack only supports usb_request objects that point to buffers
> located in memory. Support use cases where data is transferred from
> physical addresses in device mmio regions
>
> Added a bit "pre_mapped" to usb_request to bypass dma_map_single and
> dma_map_sg for such requests
>
> The caller must determine the dma address for the request before queuing
> it
>
> Signed-off-by: Manan Aurora <[email protected]>
> ---
> drivers/usb/gadget/udc/core.c | 4 ++--
> include/linux/usb/gadget.h | 1 +
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index ded9531f141b..236165ba08f4 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -900,7 +900,7 @@ EXPORT_SYMBOL_GPL(usb_gadget_activate);
> int usb_gadget_map_request_by_dev(struct device *dev,
> struct usb_request *req, int is_in)
> {
> - if (req->length == 0)
> + if (req->pre_mapped || req->length == 0)
> return 0;
>
> if (req->num_sgs) {
> @@ -948,7 +948,7 @@ 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->pre_mapped || req->length == 0)
> return;
>
> if (req->num_mapped_sgs) {
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index a771ccc038ac..6bc035439098 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -111,6 +111,7 @@ struct usb_request {
> unsigned zero:1;
> unsigned short_not_ok:1;
> unsigned dma_mapped:1;
> + unsigned pre_mapped:1;
>
> void (*complete)(struct usb_ep *ep,
> struct usb_request *req);
> --
> 2.42.0.820.g83a721a137-goog
>
>

You can not add features/functionality that no in-kernel driver uses, so
this can not be accepted as-is, sorry. Please submit it as part of a
patch series where it is actually used, otherwise we have no idea if
this is even something that we should do or not.

thanks,

greg k-h

2023-10-31 14:27:40

by Alan Stern

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