文件描述符
在linux的眼裏，everything is file！每一個設備也是一個文件。打開一個文件，這個文件對應一個唯一的正整數，直至文件關閉，內核回收文件描述符。內核（kernel）利用文件描述符（file descriptor）來訪問文件。 文件描述符是非負整數。 打開現存文件或新建文件時，內核會返回一個文件描述符。 讀寫文件也需要使用文件描述符來指定待讀寫的文件。
標準設備描述符
每個設備對應一個設備描述符，設備有多個配置（對應多個配置描述符），配置中有多個接口，接口下面又有多個端點。
USB視頻描述符層次結構
首先，闡明一個觀點，一個USB視頻設備只會暴露一個VC（video control）interface，而VS （Video control）interface是屬於VC interface或者說可以從VC（video control）interface找到VS interface。
ps：
IAD:Interface Association Descriptor 接口聯合描述符。這個描述符告訴使用者有一個VC、多少個VS、第一個是誰！
途中白框表示標準設備描述符所提供的的信息，灰色的框表示UVC自定義的特殊描述符信息（類似一些亮度，白平衡，銳化等信息都在灰色框中定義）
描述符的提取以及分析
#include <linux/atomic.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/videodev2.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/version.h>
#include <asm/unaligned.h>
#include <media/v4l2-common.h>
static const char *get_guid(const unsigned char *buf)
{
static char guid[39];
/* NOTE: see RFC 4122 for more information about GUID/UUID
* structure. The first fields fields are historically big
* endian numbers, dating from Apollo mc68000 workstations.
*/
sprintf(guid, "{%02x%02x%02x%02x"
"-%02x%02x"
"-%02x%02x"
"-%02x%02x"
"-%02x%02x%02x%02x%02x%02x}",
buf[0], buf[1], buf[2], buf[3],
buf[4], buf[5],
buf[6], buf[7],
buf[8], buf[9],
buf[10], buf[11], buf[12], buf[13], buf[14], buf[15]);
return guid;
}
static void parse_videocontrol_interface(struct usb_interface *intf, unsigned char *buf, int buflen)
{
static const char * const ctrlnames[] = {
"Brightness", "Contrast", "Hue", "Saturation", "Sharpness", "Gamma",
"White Balance Temperature", "White Balance Component", "Backlight Compensation",
"Gain", "Power Line Frequency", "Hue, Auto", "White Balance Temperature, Auto",
"White Balance Component, Auto", "Digital Multiplier", "Digital Multiplier Limit",
"Analog Video Standard", "Analog Video Lock Status"
};
static const char * const camctrlnames[] = {
"Scanning Mode", "Auto-Exposure Mode", "Auto-Exposure Priority",
"Exposure Time (Absolute)", "Exposure Time (Relative)", "Focus (Absolute)",
"Focus (Relative)", "Iris (Absolute)", "Iris (Relative)", "Zoom (Absolute)",
"Zoom (Relative)", "PanTilt (Absolute)", "PanTilt (Relative)",
"Roll (Absolute)", "Roll (Relative)", "Reserved", "Reserved", "Focus, Auto",
"Privacy"
};
static const char * const stdnames[] = {
"None", "NTSC - 525/60", "PAL - 625/50", "SECAM - 625/50",
"NTSC - 625/50", "PAL - 525/60" };
unsigned int i, ctrls, stds, n, p, termt, freq;
while (buflen > 0)
{
if (buf[1] != USB_DT_CS_INTERFACE)
printk(" Warning: Invalid descriptor\n");
else if (buf[0] < 3)
printk(" Warning: Descriptor too short\n");
printk(" VideoControl Interface Descriptor:\n"
" bLength %5u\n"
" bDescriptorType %5u\n"
" bDescriptorSubtype %5u ",
buf[0], buf[1], buf[2]);
switch (buf[2]) {
case 0x01: /* HEADER */
printk("(HEADER)\n");
n = buf[11];
if (buf[0] < 12+n)
printk(" Warning: Descriptor too short\n");
freq = buf[7] | (buf[8] << 8) | (buf[9] << 16) | (buf[10] << 24);
printk(" bcdUVC %2x.%02x\n"
" wTotalLength %5u\n"
" dwClockFrequency %5u.%06uMHz\n"
" bInCollection %5u\n",
buf[4], buf[3], buf[5] | (buf[6] << 8), freq / 1000000,
freq % 1000000, n);
for (i = 0; i < n; i++)
printk(" baInterfaceNr(%2u) %5u\n", i, buf[12+i]);
break;
case 0x02: /* INPUT_TERMINAL */
printk("(INPUT_TERMINAL)\n");
termt = buf[4] | (buf[5] << 8);
n = termt == 0x0201 ? 7 : 0;
if (buf[0] < 8 + n)
printk(" Warning: Descriptor too short\n");
printk(" bTerminalID %5u\n"
" wTerminalType 0x%04x\n"
" bAssocTerminal %5u\n",
buf[3], termt, buf[6]);
printk(" iTerminal %5u\n",
buf[7]);
if (termt == 0x0201) {
n += buf[14];
printk(" wObjectiveFocalLengthMin %5u\n"
" wObjectiveFocalLengthMax %5u\n"
" wOcularFocalLength %5u\n"
" bControlSize %5u\n",
buf[8] | (buf[9] << 8), buf[10] | (buf[11] << 8),
buf[12] | (buf[13] << 8), buf[14]);
ctrls = 0;
for (i = 0; i < 3 && i < buf[14]; i++)
ctrls = (ctrls << 8) | buf[8+n-i-1];
printk(" bmControls 0x%08x\n", ctrls);
for (i = 0; i < 19; i++)
if ((ctrls >> i) & 1)
printk(" %s\n", camctrlnames[i]);
}
break;
case 0x03: /* OUTPUT_TERMINAL */
printk("(OUTPUT_TERMINAL)\n");
termt = buf[4] | (buf[5] << 8);
if (buf[0] < 9)
printk(" Warning: Descriptor too short\n");
printk(" bTerminalID %5u\n"
" wTerminalType 0x%04x\n"
" bAssocTerminal %5u\n"
" bSourceID %5u\n"
" iTerminal %5u\n",
buf[3], termt, buf[6], buf[7], buf[8]);
break;
case 0x04: /* SELECTOR_UNIT */
printk("(SELECTOR_UNIT)\n");
p = buf[4];
if (buf[0] < 6+p)
printk(" Warning: Descriptor too short\n");
printk(" bUnitID %5u\n"
" bNrInPins %5u\n",
buf[3], p);
for (i = 0; i < p; i++)
printk(" baSource(%2u) %5u\n", i, buf[5+i]);
printk(" iSelector %5u\n",
buf[5+p]);
break;
case 0x05: /* PROCESSING_UNIT */
printk("(PROCESSING_UNIT)\n");
n = buf[7];
if (buf[0] < 10+n)
printk(" Warning: Descriptor too short\n");
printk(" bUnitID %5u\n"
" bSourceID %5u\n"
" wMaxMultiplier %5u\n"
" bControlSize %5u\n",
buf[3], buf[4], buf[5] | (buf[6] << 8), n);
ctrls = 0;
for (i = 0; i < 3 && i < n; i++)
ctrls = (ctrls << 8) | buf[8+n-i-1];
printk(" bmControls 0x%08x\n", ctrls);
for (i = 0; i < 18; i++)
if ((ctrls >> i) & 1)
printk(" %s\n", ctrlnames[i]);
stds = buf[9+n];
printk(" iProcessing %5u\n"
" bmVideoStandards 0x%2x\n", buf[8+n], stds);
for (i = 0; i < 6; i++)
if ((stds >> i) & 1)
printk(" %s\n", stdnames[i]);
break;
case 0x06: /* EXTENSION_UNIT */
printk("(EXTENSION_UNIT)\n");
p = buf[21];
n = buf[22+p];
if (buf[0] < 24+p+n)
printk(" Warning: Descriptor too short\n");
printk(" bUnitID %5u\n"
" guidExtensionCode %s\n"
" bNumControl %5u\n"
" bNrPins %5u\n",
buf[3], get_guid(&buf[4]), buf[20], buf[21]);
for (i = 0; i < p; i++)
printk(" baSourceID(%2u) %5u\n", i, buf[22+i]);
printk(" bControlSize %5u\n", buf[22+p]);
for (i = 0; i < n; i++)
printk(" bmControls(%2u) 0x%02x\n", i, buf[23+p+i]);
printk(" iExtension %5u\n",
buf[23+p+n]);
break;
default:
printk("(unknown)\n"
" Invalid desc subtype:");
break;
}
buflen -= buf[0];
buf += buf[0];
}
}
static void parse_videostreaming_interface(struct usb_interface *intf, unsigned char *buf, int buflen)
{
static const char * const colorPrims[] = { "Unspecified", "BT.709,sRGB",
"BT.470-2 (M)", "BT.470-2 (B,G)", "SMPTE 170M", "SMPTE 240M" };
static const char * const transferChars[] = { "Unspecified", "BT.709",
"BT.470-2 (M)", "BT.470-2 (B,G)", "SMPTE 170M", "SMPTE 240M",
"Linear", "sRGB"};
static const char * const matrixCoeffs[] = { "Unspecified", "BT.709",
"FCC", "BT.470-2 (B,G)", "SMPTE 170M (BT.601)", "SMPTE 240M" };
unsigned int i, m, n, p, flags, len;
while (buflen > 0)
{
if (buf[1] != USB_DT_CS_INTERFACE)
printk(" Warning: Invalid descriptor\n");
else if (buf[0] < 3)
printk(" Warning: Descriptor too short\n");
printk(" VideoStreaming Interface Descriptor:\n"
" bLength %5u\n"
" bDescriptorType %5u\n"
" bDescriptorSubtype %5u ",
buf[0], buf[1], buf[2]);
switch (buf[2]) {
case 0x01: /* INPUT_HEADER */
printk("(INPUT_HEADER)\n");
p = buf[3];
n = buf[12];
if (buf[0] < 13+p*n)
printk(" Warning: Descriptor too short\n");
printk(" bNumFormats %5u\n"
" wTotalLength %5u\n"
" bEndPointAddress %5u\n"
" bmInfo %5u\n"
" bTerminalLink %5u\n"
" bStillCaptureMethod %5u\n"
" bTriggerSupport %5u\n"
" bTriggerUsage %5u\n"
" bControlSize %5u\n",
p, buf[4] | (buf[5] << 8), buf[6], buf[7], buf[8],
buf[9], buf[10], buf[11], n);
for (i = 0; i < p; i++)
printk(
" bmaControls(%2u) %5u\n",
i, buf[13+p*n]);
break;
case 0x02: /* OUTPUT_HEADER */
printk("(OUTPUT_HEADER)\n");
p = buf[3];
n = buf[8];
if (buf[0] < 9+p*n)
printk(" Warning: Descriptor too short\n");
printk(" bNumFormats %5u\n"
" wTotalLength %5u\n"
" bEndpointAddress %5u\n"
" bTerminalLink %5u\n"
" bControlSize %5u\n",
p, buf[4] | (buf[5] << 8), buf[6], buf[7], n);
for (i = 0; i < p; i++)
printk(
" bmaControls(%2u) %5u\n",
i, buf[9+p*n]);
break;
case 0x03: /* STILL_IMAGE_FRAME */
printk("(STILL_IMAGE_FRAME)\n");
n = buf[4];
m = buf[5+4*n];
if (buf[0] < 6+4*n+m)
printk(" Warning: Descriptor too short\n");
printk(" bEndpointAddress %5u\n"
" bNumImageSizePatterns %3u\n",
buf[3], n);
for (i = 0; i < n; i++)
printk(" wWidth(%2u) %5u\n"
" wHeight(%2u) %5u\n",
i, buf[5+4*i] | (buf[6+4*i] << 8),
i, buf[7+4*i] | (buf[8+4*i] << 8));
printk(" bNumCompressionPatterns %3u\n", n);
for (i = 0; i < m; i++)
printk(" bCompression(%2u) %5u\n",
i, buf[6+4*n+i]);
break;
case 0x04: /* FORMAT_UNCOMPRESSED */
case 0x10: /* FORMAT_FRAME_BASED */
if (buf[2] == 0x04) {
printk("(FORMAT_UNCOMPRESSED)\n");
len = 27;
} else {
printk("(FORMAT_FRAME_BASED)\n");
len = 28;
}
if (buf[0] < len)
printk(" Warning: Descriptor too short\n");
flags = buf[25];
printk(" bFormatIndex %5u\n"
" bNumFrameDescriptors %5u\n"
" guidFormat %s\n"
" bBitsPerPixel %5u\n"
" bDefaultFrameIndex %5u\n"
" bAspectRatioX %5u\n"
" bAspectRatioY %5u\n"
" bmInterlaceFlags 0x%02x\n",
buf[3], buf[4], get_guid(&buf[5]), buf[21], buf[22],
buf[23], buf[24], flags);
printk(" Interlaced stream or variable: %s\n",
(flags & (1 << 0)) ? "Yes" : "No");
printk(" Fields per frame: %u fields\n",
(flags & (1 << 1)) ? 1 : 2);
printk(" Field 1 first: %s\n",
(flags & (1 << 2)) ? "Yes" : "No");
printk(" Field pattern: ");
switch ((flags >> 4) & 0x03) {
case 0:
printk("Field 1 only\n");
break;
case 1:
printk("Field 2 only\n");
break;
case 2:
printk("Regular pattern of fields 1 and 2\n");
break;
case 3:
printk("Random pattern of fields 1 and 2\n");
break;
}
printk(" bCopyProtect %5u\n", buf[26]);
if (buf[2] == 0x10)
printk(" bVariableSize %5u\n", buf[27]);
break;
case 0x05: /* FRAME UNCOMPRESSED */
case 0x07: /* FRAME_MJPEG */
case 0x11: /* FRAME_FRAME_BASED */
if (buf[2] == 0x05) {
printk("(FRAME_UNCOMPRESSED)\n");
n = 25;
} else if (buf[2] == 0x07) {
printk("(FRAME_MJPEG)\n");
n = 25;
} else {
printk("(FRAME_FRAME_BASED)\n");
n = 21;
}
len = (buf[n] != 0) ? (26+buf[n]*4) : 38;
if (buf[0] < len)
printk(" Warning: Descriptor too short\n");
flags = buf[4];
printk(" bFrameIndex %5u\n"
" bmCapabilities 0x%02x\n",
buf[3], flags);
printk(" Still image %ssupported\n",
(flags & (1 << 0)) ? "" : "un");
if (flags & (1 << 1))
printk(" Fixed frame-rate\n");
printk(" wWidth %5u\n"
" wHeight %5u\n"
" dwMinBitRate %9u\n"
" dwMaxBitRate %9u\n",
buf[5] | (buf[6] << 8), buf[7] | (buf[8] << 8),
buf[9] | (buf[10] << 8) | (buf[11] << 16) | (buf[12] << 24),
buf[13] | (buf[14] << 8) | (buf[15] << 16) | (buf[16] << 24));
if (buf[2] == 0x11)
printk(" dwDefaultFrameInterval %9u\n"
" bFrameIntervalType %5u\n"
" dwBytesPerLine %9u\n",
buf[17] | (buf[18] << 8) | (buf[19] << 16) | (buf[20] << 24),
buf[21],
buf[22] | (buf[23] << 8) | (buf[24] << 16) | (buf[25] << 24));
else
printk(" dwMaxVideoFrameBufferSize %9u\n"
" dwDefaultFrameInterval %9u\n"
" bFrameIntervalType %5u\n",
buf[17] | (buf[18] << 8) | (buf[19] << 16) | (buf[20] << 24),
buf[21] | (buf[22] << 8) | (buf[23] << 16) | (buf[24] << 24),
buf[25]);
if (buf[n] == 0)
printk(" dwMinFrameInterval %9u\n"
" dwMaxFrameInterval %9u\n"
" dwFrameIntervalStep %9u\n",
buf[26] | (buf[27] << 8) | (buf[28] << 16) | (buf[29] << 24),
buf[30] | (buf[31] << 8) | (buf[32] << 16) | (buf[33] << 24),
buf[34] | (buf[35] << 8) | (buf[36] << 16) | (buf[37] << 24));
else
for (i = 0; i < buf[n]; i++)
printk(" dwFrameInterval(%2u) %9u\n",
i, buf[26+4*i] | (buf[27+4*i] << 8) |
(buf[28+4*i] << 16) | (buf[29+4*i] << 24));
break;
case 0x06: /* FORMAT_MJPEG */
printk("(FORMAT_MJPEG)\n");
if (buf[0] < 11)
printk(" Warning: Descriptor too short\n");
flags = buf[5];
printk(" bFormatIndex %5u\n"
" bNumFrameDescriptors %5u\n"
" bFlags %5u\n",
buf[3], buf[4], flags);
printk(" Fixed-size samples: %s\n",
(flags & (1 << 0)) ? "Yes" : "No");
flags = buf[9];
printk(" bDefaultFrameIndex %5u\n"
" bAspectRatioX %5u\n"
" bAspectRatioY %5u\n"
" bmInterlaceFlags 0x%02x\n",
buf[6], buf[7], buf[8], flags);
printk(" Interlaced stream or variable: %s\n",
(flags & (1 << 0)) ? "Yes" : "No");
printk(" Fields per frame: %u fields\n",
(flags & (1 << 1)) ? 2 : 1);
printk(" Field 1 first: %s\n",
(flags & (1 << 2)) ? "Yes" : "No");
printk(" Field pattern: ");
switch ((flags >> 4) & 0x03) {
case 0:
printk("Field 1 only\n");
break;
case 1:
printk("Field 2 only\n");
break;
case 2:
printk("Regular pattern of fields 1 and 2\n");
break;
case 3:
printk("Random pattern of fields 1 and 2\n");
break;
}
printk(" bCopyProtect %5u\n", buf[10]);
break;
case 0x0a: /* FORMAT_MPEG2TS */
printk("(FORMAT_MPEG2TS)\n");
len = buf[0] < 23 ? 7 : 23;
if (buf[0] < len)
printk(" Warning: Descriptor too short\n");
printk(" bFormatIndex %5u\n"
" bDataOffset %5u\n"
" bPacketLength %5u\n"
" bStrideLength %5u\n",
buf[3], buf[4], buf[5], buf[6]);
if (len > 7)
printk(" guidStrideFormat %s\n",
get_guid(&buf[7]));
break;
case 0x0d: /* COLORFORMAT */
printk("(COLORFORMAT)\n");
if (buf[0] < 6)
printk(" Warning: Descriptor too short\n");
printk(" bColorPrimaries %5u (%s)\n",
buf[3], (buf[3] <= 5) ? colorPrims[buf[3]] : "Unknown");
printk(" bTransferCharacteristics %5u (%s)\n",
buf[4], (buf[4] <= 7) ? transferChars[buf[4]] : "Unknown");
printk(" bMatrixCoefficients %5u (%s)\n",
buf[5], (buf[5] <= 5) ? matrixCoeffs[buf[5]] : "Unknown");
break;
default:
printk(" Invalid desc subtype:");
break;
}
buflen -= buf[0];
buf += buf[0];
}
}
static void dump_endpoint(const struct usb_endpoint_descriptor *endpoint)
{
static const char * const typeattr[] = {
"Control",
"Isochronous",
"Bulk",
"Interrupt"
};
static const char * const syncattr[] = {
"None",
"Asynchronous",
"Adaptive",
"Synchronous"
};
static const char * const usage[] = {
"Data",
"Feedback",
"Implicit feedback Data",
"(reserved)"
};
static const char * const hb[] = { "1x", "2x", "3x", "(?\?)" };
unsigned wmax = __le16_to_cpu(endpoint->wMaxPacketSize);
printk(" Endpoint Descriptor:\n"
" bLength %5u\n"
" bDescriptorType %5u\n"
" bEndpointAddress 0x%02x EP %u %s\n"
" bmAttributes %5u\n"
" Transfer Type %s\n"
" Synch Type %s\n"
" Usage Type %s\n"
" wMaxPacketSize 0x%04x %s %d bytes\n"
" bInterval %5u\n",
endpoint->bLength,
endpoint->bDescriptorType,
endpoint->bEndpointAddress,
endpoint->bEndpointAddress & 0x0f,
(endpoint->bEndpointAddress & 0x80) ? "IN" : "OUT",
endpoint->bmAttributes,
typeattr[endpoint->bmAttributes & 3],
syncattr[(endpoint->bmAttributes >> 2) & 3],
usage[(endpoint->bmAttributes >> 4) & 3],
wmax, hb[(wmax >> 11) & 3], wmax & 0x7ff,
endpoint->bInterval);
/* only for audio endpoints */
if (endpoint->bLength == 9)
printk(" bRefresh %5u\n"
" bSynchAddress %5u\n",
endpoint->bRefresh, endpoint->bSynchAddress);
}
static int myuvc_probe(struct usb_interface *intf,
const struct usb_device_id *id)
{
static int cnt;
struct usb_device *dev = interface_to_usbdev(intf);
struct usb_device_descriptor *descriptor = &dev->descriptor;
struct usb_host_config *hostconfig;
struct usb_config_descriptor *config;
struct usb_interface_assoc_descriptor *assoc_desc;
struct usb_interface_descriptor *interface;
struct usb_endpoint_descriptor *endpoint;
int i,j,k,l,m;
unsigned char *buffer;
int buflen;
int desc_len;
int desc_cnt;
printk("myuvc_probe : cnt = %d\n", cnt++);
/* 打印設備描述符 */
printk("Device Descriptor:\n"
" bLength %5u\n"
" bDescriptorType %5u\n"
" bcdUSB %2x.%02x\n"
" bDeviceClass %5u \n"
" bDeviceSubClass %5u \n"
" bDeviceProtocol %5u \n"
" bMaxPacketSize0 %5u\n"
" idVendor 0x%04x \n"
" idProduct 0x%04x \n"
" bcdDevice %2x.%02x\n"
" iManufacturer %5u\n"
" iProduct %5u\n"
" iSerial %5u\n"
" bNumConfigurations %5u\n",
descriptor->bLength, descriptor->bDescriptorType,
descriptor->bcdUSB >> 8, descriptor->bcdUSB & 0xff,
descriptor->bDeviceClass,
descriptor->bDeviceSubClass,
descriptor->bDeviceProtocol,
descriptor->bMaxPacketSize0,
descriptor->idVendor, descriptor->idProduct,
descriptor->bcdDevice >> 8, descriptor->bcdDevice & 0xff,
descriptor->iManufacturer,
descriptor->iProduct,
descriptor->iSerialNumber,
descriptor->bNumConfigurations);
for (i=0;i<descriptor->bNumConfigurations;i++)
{
hostconfig = &dev->config[i]; /*把這個配置地址取出來一下*/
config = &hostconfig->desc; /*把配置描述符取出來*/
printk(" Configuration Descriptor %d:\n"
" bLength %5u\n"
" bDescriptorType %5u\n"
" wTotalLength %5u\n"
" bNumInterfaces %5u\n"
" bConfigurationValue %5u\n"
" iConfiguration %5u\n"
" bmAttributes 0x%02x\n",
i,
config->bLength, config->bDescriptorType,
__le16_to_cpu(config->wTotalLength),
config->bNumInterfaces, config->bConfigurationValue,
config->iConfiguration,
config->bmAttributes);
/*打印的是接口聯合體運算符*/
assoc_desc = hostconfig->intf_assoc[0]; /*這裏爲什麼不加 取址：原因是這個數組裏面全是指針*/
printk(" Interface Association:\n"
" bLength %5u\n"
" bDescriptorType %5u\n"
" bFirstInterface %5u\n"
" bInterfaceCount %5u\n"
" bFunctionClass %5u\n"
" bFunctionSubClass %5u\n"
" bFunctionProtocol %5u\n"
" iFunction %5u\n",
assoc_desc->bLength,
assoc_desc->bDescriptorType,
assoc_desc->bFirstInterface,
assoc_desc->bInterfaceCount,
assoc_desc->bFunctionClass,
assoc_desc->bFunctionSubClass,
assoc_desc->bFunctionProtocol,
assoc_desc->iFunction);
/*打印接口描述符*/
/*打印該接口下面的多個設置*/
/*這裏的設置就是描述符的信息*/
for (j=0;j<intf->num_altsetting;j++)
{
interface = &intf->altsetting[j].desc;
printk(" Interface Descriptor altsetting %d:\n"
" bLength %5u\n"
" bDescriptorType %5u\n"
" bInterfaceNumber %5u\n"
" bAlternateSetting %5u\n"
" bNumEndpoints %5u\n"
" bInterfaceClass %5u\n"
" bInterfaceSubClass %5u\n"
" bInterfaceProtocol %5u\n"
" iInterface %5u\n",
j,
interface->bLength, interface->bDescriptorType, interface->bInterfaceNumber,
interface->bAlternateSetting, interface->bNumEndpoints, interface->bInterfaceClass,
interface->bInterfaceSubClass, interface->bInterfaceProtocol,
interface->iInterface);
/* 打印端點描述符 */
for (m = 0; m < interface->bNumEndpoints; m++)
{
endpoint = &intf->altsetting[j].endpoint[m].desc;
dump_endpoint(endpoint);
}
}
buffer = intf->cur_altsetting->extra; /*UVC類所定義的描述符都在extra裏面*/
buflen = intf->cur_altsetting->extralen;
printk("extra buffer of interface %d:\n", cnt-1);
k = 0;
desc_cnt = 0;
while (k < buflen)
{
desc_len = buffer[k];
printk("extra desc %d: ", desc_cnt);
for (l = 0; l < desc_len; l++, k++)
{
printk("%02x ", buffer[k]);
}
desc_cnt++;
printk("\n");
}
/*分析UVC自定義的描述符*/
interface = &intf->cur_altsetting->desc;
if ((buffer[1] == USB_DT_CS_INTERFACE) && (interface->bInterfaceSubClass == 1))
{
/*解析VC的數據*/
parse_videocontrol_interface(intf, buffer, buflen);
}
if ((buffer[1] == USB_DT_CS_INTERFACE) && (interface->bInterfaceSubClass == 2))
{
/*分析VS interface的信息*/
parse_videostreaming_interface(intf, buffer, buflen);
}
}
return 0;
}
static void myuvc_disconnect(struct usb_interface *intf)
{
static int cnt;
printk("myuvc_disconnect : cnt = %d\n", cnt++);
}
/*myuvc_ids裏面可以填充某個廠家特定的設備，也可以填充通用的設備*/
/*內核比對id成功一次調用一次probe函數，拔除設備時一樣會比對id調用myuvc_disconnect函數*/
/*這是是兩個通用設備，所以會調用兩次*/
static struct usb_device_id myuvc_ids[] = {
/* Generic USB Video Class */
/*這個設備屬於USB_CLASS_VIDEO類，子類是1（VIDEOControl視頻控制接口），協議是0*/
/*流接口屬於控制接口，可以通過控制接口找到流接口*/
{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 1, 0) }, /*VdieoControl Interface*/
{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 2, 0) }, /*VdieoStreaming Interface*/
{}
};
/*1.分配一個usb_driver結構體*/
/*2.設置*/
/*id_table表示支持哪些設備*/
/*probe表示接上支持的設備時，probe函數就會被調用*/
/*disconnect表示拔除設備後會調用該函數進行銷燬的工作*/
static struct usb_driver myuvc_driver = {
.name = "myuvc",
.probe = myuvc_probe,
.disconnect = myuvc_disconnect,
.id_table = myuvc_ids,
};
static int myuvc_init(void)
{
/*註冊*/
usb_register(&myuvc_driver);
return 0;
}
static void myuvc_exit(void)
{
usb_deregister(&myuvc_driver);
}
module_init(myuvc_init);
module_exit(myuvc_exit);
MODULE_LICENSE("GPL");
對於設備的成功調用與否，需要比對id_table中的信息，裏面可以是特定廠家提供的設備，也可以是通用設備。
自定義描述符的內容
VideoControl Interface的自定義描述符:
extra buffer of interface 0:
extra desc 0: 0d 24 01 00 01 4d 00 80 c3 c9 01 01 01
第一個字節表示該描述符的長度，第二個字節標書CS(class special)類型，第三個字節表示子類型，一次按着TABLE 3-3比對解析。
VC_INPUT_TERMINAL （IT） ：
extra desc 1: 12 24 02 01 01 02 00 00 00 00 00 00 00 00 03 0e 00 00
VC_OUTPUT_TERMINAL (OT)：
extra desc 2: 09 24 03 02 01 01 00 04 00
VC_PROCESSING_UNIT (PU):
extra desc 3: 0b 24 05 03 01 00 00 02 7f 14 00
VC_EXTENSION_UNIT (EU):
extra desc 4: 1a 24 06 04 ad cc b1 c2 f6 ab b8 48 8e 37 32 d4 f3 a3 fe ec 08 01 03 01 3f 00
根據描述符中的信息，可以的到VC interface中內部的結構：
IT(01) ===> PU(03) ===> EU(04) ===> OT(02)
VideoStreaming Interface的自定義描述符:
VS_INPUT_HEADER ：
extra desc 0: 0e 24 01 01 df 00 81 00 02 02 01 01 01 00
VS_FORMAT_UNCOMPRESSED ：
extra desc 1: 1b 24 04 01 05 59 55 59 32 00 00 10 00 80 00 00 aa 00 38 9b 71 10 01 00 00 00 00
