1#include <linux/usb.h>
 2#include <linux/usb/hcd.h>
 3#include "usb.h"
 4
 5static int uas_is_interface(struct usb_host_interface *intf)
 6{
 7	return (intf->desc.bInterfaceClass == USB_CLASS_MASS_STORAGE &&
 8		intf->desc.bInterfaceSubClass == USB_SC_SCSI &&
 9		intf->desc.bInterfaceProtocol == USB_PR_UAS);
10}
11
12static int uas_isnt_supported(struct usb_device *udev)
13{
14	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
15
16	dev_warn(&udev->dev, "The driver for the USB controller %s does not "
17			"support scatter-gather which is\n",
18			hcd->driver->description);
19	dev_warn(&udev->dev, "required by the UAS driver. Please try an"
20			"alternative USB controller if you wish to use UAS.\n");
21	return -ENODEV;
22}
23
24static int uas_find_uas_alt_setting(struct usb_interface *intf)
25{
26	int i;
27	struct usb_device *udev = interface_to_usbdev(intf);
28	int sg_supported = udev->bus->sg_tablesize != 0;
29
30	for (i = 0; i < intf->num_altsetting; i++) {
31		struct usb_host_interface *alt = &intf->altsetting[i];
32
33		if (uas_is_interface(alt)) {
34			if (!sg_supported)
35				return uas_isnt_supported(udev);
36			return alt->desc.bAlternateSetting;
37		}
38	}
39
40	return -ENODEV;
41}
42
43static int uas_find_endpoints(struct usb_host_interface *alt,
44			      struct usb_host_endpoint *eps[])
45{
46	struct usb_host_endpoint *endpoint = alt->endpoint;
47	unsigned i, n_endpoints = alt->desc.bNumEndpoints;
48
49	for (i = 0; i < n_endpoints; i++) {
50		unsigned char *extra = endpoint[i].extra;
51		int len = endpoint[i].extralen;
52		while (len >= 3) {
53			if (extra[1] == USB_DT_PIPE_USAGE) {
54				unsigned pipe_id = extra[2];
55				if (pipe_id > 0 && pipe_id < 5)
56					eps[pipe_id - 1] = &endpoint[i];
57				break;
58			}
59			len -= extra[0];
60			extra += extra[0];
61		}
62	}
63
64	if (!eps[0] || !eps[1] || !eps[2] || !eps[3])
65		return -ENODEV;
66
67	return 0;
68}
69
70static int uas_use_uas_driver(struct usb_interface *intf,
71			      const struct usb_device_id *id)
72{
73	struct usb_host_endpoint *eps[4] = { };
74	struct usb_device *udev = interface_to_usbdev(intf);
75	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
76	unsigned long flags = id->driver_info;
77	int r, alt;
78
79	usb_stor_adjust_quirks(udev, &flags);
80
81	if (flags & US_FL_IGNORE_UAS)
82		return 0;
83
84	if (udev->speed >= USB_SPEED_SUPER && !hcd->can_do_streams)
85		return 0;
86
87	alt = uas_find_uas_alt_setting(intf);
88	if (alt < 0)
89		return 0;
90
91	r = uas_find_endpoints(&intf->altsetting[alt], eps);
92	if (r < 0)
93		return 0;
94
95	return 1;
96}