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USB: core: add helpers to retrieve endpoints

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Many USB drivers iterate over the available endpoints to find required
endpoints of a specific type and direction. Typically the endpoints are
required for proper function and a missing endpoint should abort probe.

To facilitate code reuse, add a helper to retrieve common endpoints
(bulk or interrupt, in or out) and four wrappers to find a single
endpoint.

Note that the helpers are marked as __must_check to serve as a reminder
to always verify that all expected endpoints are indeed present. This
also means that any optional endpoints, typically need to be looked up
through separate calls.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2017-03-17 11:35:30 +01:00 committed by Greg Kroah-Hartman
parent 96cfcc9c46
commit 66a359390e
2 changed files with 118 additions and 0 deletions
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83
drivers/usb/core/usb.c
View File

@ -75,6 +75,89 @@ MODULE_PARM_DESC(autosuspend, "default autosuspend delay");
#endif
/**
* usb_find_common_endpoints() -- look up common endpoint descriptors
* @alt: alternate setting to search
* @bulk_in: pointer to descriptor pointer, or NULL
* @bulk_out: pointer to descriptor pointer, or NULL
* @int_in: pointer to descriptor pointer, or NULL
* @int_out: pointer to descriptor pointer, or NULL
*
* Search the alternate setting's endpoint descriptors for the first bulk-in,
* bulk-out, interrupt-in and interrupt-out endpoints and return them in the
* provided pointers (unless they are NULL).
*
* If a requested endpoint is not found, the corresponding pointer is set to
* NULL.
*
* Return: Zero if all requested descriptors were found, or -ENXIO otherwise.
*/
int usb_find_common_endpoints(struct usb_host_interface *alt,
struct usb_endpoint_descriptor **bulk_in,
struct usb_endpoint_descriptor **bulk_out,
struct usb_endpoint_descriptor **int_in,
struct usb_endpoint_descriptor **int_out)
{
struct usb_endpoint_descriptor *epd;
int i;
if (bulk_in)
*bulk_in = NULL;
if (bulk_out)
*bulk_out = NULL;
if (int_in)
*int_in = NULL;
if (int_out)
*int_out = NULL;
for (i = 0; i < alt->desc.bNumEndpoints; ++i) {
epd = &alt->endpoint[i].desc;
switch (usb_endpoint_type(epd)) {
case USB_ENDPOINT_XFER_BULK:
if (usb_endpoint_dir_in(epd)) {
if (bulk_in && !*bulk_in) {
*bulk_in = epd;
break;
}
} else {
if (bulk_out && !*bulk_out) {
*bulk_out = epd;
break;
}
}
continue;
case USB_ENDPOINT_XFER_INT:
if (usb_endpoint_dir_in(epd)) {
if (int_in && !*int_in) {
*int_in = epd;
break;
}
} else {
if (int_out && !*int_out) {
*int_out = epd;
break;
}
}
continue;
default:
continue;
}
if ((!bulk_in || *bulk_in) &&
(!bulk_out || *bulk_out) &&
(!int_in || *int_in) &&
(!int_out || *int_out)) {
return 0;
}
}
return -ENXIO;
}
EXPORT_SYMBOL_GPL(usb_find_common_endpoints);
/**
* usb_find_alt_setting() - Given a configuration, find the alternate setting
* for the given interface.

35
include/linux/usb.h
View File

@ -99,6 +99,41 @@ enum usb_interface_condition {
USB_INTERFACE_UNBINDING,
};
int __must_check
usb_find_common_endpoints(struct usb_host_interface *alt,
struct usb_endpoint_descriptor **bulk_in,
struct usb_endpoint_descriptor **bulk_out,
struct usb_endpoint_descriptor **int_in,
struct usb_endpoint_descriptor **int_out);
static inline int __must_check
usb_find_bulk_in_endpoint(struct usb_host_interface *alt,
struct usb_endpoint_descriptor **bulk_in)
{
return usb_find_common_endpoints(alt, bulk_in, NULL, NULL, NULL);
}
static inline int __must_check
usb_find_bulk_out_endpoint(struct usb_host_interface *alt,
struct usb_endpoint_descriptor **bulk_out)
{
return usb_find_common_endpoints(alt, NULL, bulk_out, NULL, NULL);
}
static inline int __must_check
usb_find_int_in_endpoint(struct usb_host_interface *alt,
struct usb_endpoint_descriptor **int_in)
{
return usb_find_common_endpoints(alt, NULL, NULL, int_in, NULL);
}
static inline int __must_check
usb_find_int_out_endpoint(struct usb_host_interface *alt,
struct usb_endpoint_descriptor **int_out)
{
return usb_find_common_endpoints(alt, NULL, NULL, NULL, int_out);
}
/**
* struct usb_interface - what usb device drivers talk to
* @altsetting: array of interface structures, one for each alternate