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Xenomai API
2.6.4
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Data Structures | |
| struct | a4l_descriptor |
| Structure containing device-information useful to users. More... | |
Functions | |
| int | a4l_sys_desc (int fd, a4l_desc_t *dsc, int pass) |
| Get a descriptor on an attached device. | |
ANALOGY_xxx_DESC | |
Constants used as argument so as to define the description depth to recover | |
| #define | A4L_BSC_DESC 0x0 |
| BSC stands for basic descriptor (device data) | |
| #define | A4L_CPLX_DESC 0x1 |
| CPLX stands for complex descriptor (subdevice + channel + range data) | |
| int a4l_sys_desc | ( | int | fd, |
| a4l_desc_t * | dsc, | ||
| int | pass | ||
| ) |
Get a descriptor on an attached device.
Once the device has been attached, the function a4l_get_desc() retrieves various information on the device (subdevices, channels, ranges, etc.). The function a4l_get_desc() can be called twice:
Between the two calls, an allocation must be performed in order to recover a buffer large enough to contain all the data. These data are set up according a root-leaf organization (device -> subdevice -> channel -> range). They cannot be accessed directly; specific functions are available so as to retrieve them:
| [in] | fd | Driver file descriptor |
| [out] | dsc | Device descriptor |
| [in] | pass | Description level to retrieve:
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References A4L_BSC_DESC, a4l_descriptor::magic, a4l_descriptor::sbdata, and a4l_descriptor::sbsize.
Referenced by a4l_fill_desc(), and a4l_open().