Comtrol eCos - Manual (Page 367)

Chapter 15. User API
All functions, except cyg_io_lookup() require an I/O “handle”.
All functions return a value of the type Cyg_ErrNo. If an error condition is detected, this value will be negative and
the absolute value indicates the actual error, as specified in
cyg/error/codes.h . The only other legal return value
will be ENOERR . All other function arguments are pointers (references). This allows the drivers to pass information
efficiently, both into and out of the driver. The most striking example of this is the “length” value passed to the
read and write functions. This parameter contains the desired length of data on input to the function and the actual
transferred length on return.
// Lookup a device and return its handle
Cyg_ErrNo cyg_io_lookup (
const char *name,
cyg_io_handle_t *handle )
This function maps a device name onto an appropriate handle. If the named device is not in the system, then the
error
-ENOENT is returned. If the device is found, then the handle for the device is returned by way of the handle
pointer *handle .
// Write data to a device
Cyg_ErrNo cyg_io_write (
cyg_io_handle_t handle,
const void *buf,
cyg_uint32 *len )
This function sends data to a device. The size of data to send is contained in *len and the actual size sent will be
returned in the same place.
// Read data from a device
Cyg_ErrNo cyg_io_read (
cyg_io_handle_t handle,
void *buf,
cyg_uint32 *len )
This function receives data from a device. The desired size of data to receive is contained in *len and the actual
size obtained will be returned in the same place.
// Get the configuration of a device
Cyg_ErrNo cyg_io_get_config (
cyg_io_handle_t handle,
cyg_uint32 key ,
void *buf,
cyg_uint32 *len )
This function is used to obtain run-time configuration about a device. The type of information retrieved is specified
by the
key . The data will be returned in the given buffer. The value of *len should contain the amount of
data requested, which must be at least as large as the size appropriate to the selected key. The actual size of
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