sound/usb/helper.c

Source file repositories/reference/linux-study-clean/sound/usb/helper.c

File Facts

System
Linux kernel
Corpus path
sound/usb/helper.c
Extension
.c
Size
3770 bytes
Lines
168
Domain
Driver Families
Bucket
sound/usb
Inferred role
Driver Families: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

if (p[1] == dtype && (!after || (void *)p > after)) {
			return p;
		}
		p = next;
	}
	return NULL;
}

/*
 * find a class-specified interface descriptor with the given subtype.
 */
void *snd_usb_find_csint_desc(void *buffer, int buflen, void *after, u8 dsubtype)
{
	unsigned char *p = after;

	while ((p = snd_usb_find_desc(buffer, buflen, p,
				      USB_DT_CS_INTERFACE)) != NULL) {
		if (p[0] >= 3 && p[2] == dsubtype)
			return p;
	}
	return NULL;
}
EXPORT_SYMBOL_GPL(snd_usb_find_csint_desc);

/*
 * Wrapper for usb_control_msg().
 * Allocates a temp buffer to prevent dmaing from/to the stack.
 */
int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
		    __u8 requesttype, __u16 value, __u16 index, void *data,
		    __u16 size)
{
	int err;
	void *buf = NULL;
	int timeout;

	if (usb_pipe_type_check(dev, pipe))
		return -EINVAL;

	if (size > 0) {
		buf = kmemdup(data, size, GFP_KERNEL);
		if (!buf)
			return -ENOMEM;
	}

	if (requesttype & USB_DIR_IN)
		timeout = USB_CTRL_GET_TIMEOUT;
	else
		timeout = USB_CTRL_SET_TIMEOUT;

	err = usb_control_msg(dev, pipe, request, requesttype,
			      value, index, buf, size, timeout);

	if (size > 0) {
		memcpy(data, buf, size);
		kfree(buf);
	}

	snd_usb_ctl_msg_quirk(dev, pipe, request, requesttype,
			      value, index, data, size);

	return err;
}

unsigned char snd_usb_parse_datainterval(struct snd_usb_audio *chip,
					 struct usb_host_interface *alts)
{
	switch (snd_usb_get_speed(chip->dev)) {
	case USB_SPEED_HIGH:
	case USB_SPEED_SUPER:
	case USB_SPEED_SUPER_PLUS:
		if (get_endpoint(alts, 0)->bInterval >= 1 &&
		    get_endpoint(alts, 0)->bInterval <= 4)
			return get_endpoint(alts, 0)->bInterval - 1;
		break;
	default:
		break;
	}
	return 0;
}

struct usb_host_interface *
snd_usb_get_host_interface(struct snd_usb_audio *chip, int ifnum, int altsetting)
{
	struct usb_interface *iface;

	iface = usb_ifnum_to_if(chip->dev, ifnum);
	if (!iface)
		return NULL;
	return usb_altnum_to_altsetting(iface, altsetting);

Annotation

Implementation Notes