usb_get_max_pkts_per_isocKernelsFunctionsusb_get_max_pkts_per_isoc_request(9F)NAMEusb_get_max_pkts_per_isoc_request - Get maximum number of packets
allowed per isochronous request
SYNOPSIS
#include <sys/usb/usba.h>
uint_t usb_get_max_pkts_per_isoc_request(dev_info_t *dip);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI)
PARAMETERS
dip
Pointer to the device's dev_info structure.
DESCRIPTION
The usb_get_max_pkts_per_isoc_request() function returns the maximum
number of isochronous packets per request that the host control driver
can support. This number can be used to determine the maximum amount of
data which can be handled by a single isochronous request. That
length is found by:
max = usb_get_max_pkts_per_isoc_request(dip) * endpoint_max_packet_size;
where endpoint_max_packet_size is the wMaxPacketSize field of the
isochronous endpoint over which the transfer will take place.
RETURN VALUES
On success, the usb_get_current_frame_number() function returns the
maximum number of isochronous pkts per request. On failure it returns
0. The function fails if dip is NULL.
CONTEXT
May be called from user, kernel or interrupt context.
EXAMPLES
/*
* Set up to receive periodic isochronous data, requesting
* the maximum amount for each transfer.
*/
int pkt;
/* Get max packet size from endpoint descriptor. */
uint_t ep_max_pkt_size = ep_descr.wMaxPacketSize;
uint_t isoc_pkts_count = usb_get_max_pkts_per_isoc_request(dip);
/*
* Allocate an isoc request, specifying the max number of packets
* and the greatest size transfer possible.
*/
usb_isoc_req_t *isoc_req = usb_alloc_isoc_req(dip,
isoc_pkts_count,
isoc_pkts_count * ep_max_pkt_size,
USB_FLAGS_SLEEP);
/* Init each packet descriptor for maximum size. */
for (pkt = 0; pkt < isoc_pkts_count; pkt++) {
isoc_req->isoc_pkt_descr[pkt].isoc_pkt_length = ep_max_pkt_size;
}
/* Set the length of a packet in the request too. */
isoc_req->isoc_pkts_length = ep_max_pkt_size;
/* Other isoc request initialization. */
...
...
if (usb_pipe_isoc_xfer(pipe, isoc_req, USB_FLAGS_NOSLEEP) != USB_SUCCESS) {
...
}
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Architecture │PCI-based systems │
├─────────────────────────────┼─────────────────────────────┤
│Interface stability │Evolving │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWusb │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOattributes(5), usb_pipe_isoc_xfer(9F), usb_alloc_request(9F),
usb_get_current_frame_number(9F). usb_ep_descr(9S),
usb_isoc_request(9S)SunOS 5.10 5 Jan 2usb_get_max_pkts_per_isoc_request(9F)
