SYNOPSIS
#include <hal.h>
typedef int (*hal_query_cb)(hal_query_t *query, void *arg);
int hal_set_p(hal_query_t *query, hal_query_cb callback, void *arg);ARGUMENTS
- query
-
The query structure containing the name to search for and value to set.
- callback
-
The callback function to invoke when the pin or param has been found to get the value to set. This can also be NULL if no callback is required. Both query.pp.value and query.pp.type must be appropriately set if callback is NULL.
- arg
-
A user defined pointer to a user defined data structure. The arg pointer is passed verbatim to the callback function.
DESCRIPTION
The hal_set_p() function will find the named pin or param and set its value to the user supplied value. The query structure should be set to zero before the call, except for the fields noted below.
The query.name must be set to the name of the pin or parameter you want to set. Optionally, you can enforce to look exclusively for a pin or param by setting query.qtype before the call to:
-
0- look for either pin or param -
HAL_QTYPE_PIN- only look for a pin -
HAL_QTYPE_PARAM- only look for a param
Note that both pins and params share one namespace and cannot overlap.
You can further limit the search by setting query.pp.type to the HAL type you want to set. If the pin or param is found, but has a different type, then -EEXIST is returned.
Setting a pin connected to a signal or a pin of direction HAL_OUT will fail with an -EACCES error.
Setting a param of direction HAL_RO will fail with an -EACCES error.
The callback is called with all fields set appropriately, including data reference. You must set the correct query.pp.value subfield in the callback according to the query.pp.type field. The pin’s or param’s value will be set if the callback returns with zero (0).
If you do not wish to use a callback, then you must set both query.pp.type and query.pp.value beforehand. The actual type will be checked against what is found and a mismatch will result in an -EEXIST error.
If found, hal_set_p() sets the query.name field to the actual live pin or param name. The query.qtype field is set accordingly to whether a pin or a param was found.
RETURN VALUE
The hal_set_p() function returns zero (0) on success. The return value of the callback is returned if it got called and was non-zero. A negative errno code is returned if any problem is detected:
| -EFAULT |
The shared memory was not mapped. |
| -EINVAL |
An invalid argument was passed. |
| -ENOENT |
The pin or param does not exist. |
| -EEXIST |
The pin or param exists but is of different type. |
| -EACCES |
Trying to write a |
| -EBADF |
Attempt to set a |
| -EIO |
The internal data pointer is missing. |
EXAMPLES
int set_pin_fpval(const char *ppname, rtapi_real val)
{
hal_query_t query = {};
query.name = ppname;
query.qtype = HAL_QTYPE_PIN; // Only look for pins
query.pp.type = HAL_REAL; // We want to set a floating point value
query.pp.value.r = val; // This is the value
int rv = hal_set_p(&query, NULL, NULL);
if(0 != rv)
printf("Failed to set '%s': %s\n", ppname, hal_strerror(rv));
return rv;
}static int ppsetter_cb(hal_query_t *query, void *arg)
{
const char *str = (const char *)arg;
// Perform conversion based on type
switch(query->pp.type) {
case HAL_BOOL: query->pp.value.b = str2bool(str); break;
case HAL_REAL: query->pp.value.r = str2real(str); break;
case HAL_SINT: query->pp.value.s = str2sint(str); break;
case HAL_UINT: query->pp.value.u = str2uint(str); break;
default:
printf("unsupported value type %d\n", (int)query->pp.type);
return -EBADF;
}
return 0;
}
int set_p_val(const char *ppname, const char *str)
{
hal_query_t query = {};
query.name = ppname;
int rv = hal_set_p(&query, ppsetter_cb, (void *)str);
if(0 != rv)
printf("Failed to set '%s' to '%s': %s\n", ppname, str, hal_strerror(rv));
return rv;
}