Fake Power provider example

Example provider - provides fake power supply properties. More...

Classes
struct	statefs_power_prop
struct	power_handle

Macros
#define	iv_max_size   (sizeof(max_iv_fmt) - 1)
#define	is_low_max_len   sizeof(is_low_fmt)

Functions
static void *	control_thread (void *)
static int	power_init ()
static int	read_voltage (char *dst, statefs_size_t len)
static int	read_current (char *dst, statefs_size_t len)
static bool	update_is_low ()
static int	read_is_low (char *dst, statefs_size_t len)
static struct statefs_power_prop *	power_prop (struct statefs_property *p)
static struct statefs_node *	prop_find (struct statefs_branch const *self, char const *name)
static void	prop_next (struct statefs_branch const *self, statefs_handle_t *idx_ptr)
static struct statefs_node *	prop_get (struct statefs_branch const *self, statefs_handle_t idx)
static statefs_handle_t	prop_first (struct statefs_branch const *self)
static struct statefs_node *	ns_find (struct statefs_branch const *self, char const *name)
static struct statefs_node *	ns_get (struct statefs_branch const *self, statefs_handle_t p)
static statefs_handle_t	ns_first (struct statefs_branch const *self)
static void	power_release (struct statefs_node *node)
static bool	power_connect (struct statefs_property *p, struct statefs_slot *slot)
static void	power_disconnect (struct statefs_property *p)
static int	power_getattr (struct statefs_property const *p)
static statefs_ssize_t	power_size (struct statefs_property const *p)
static statefs_handle_t	power_open (struct statefs_property *p, int mode)
static int	power_read (statefs_handle_t h, char *dst, statefs_size_t len, statefs_off_t off)
static void	power_close (statefs_handle_t h)

Variables
static pthread_mutex_t	power_mutex = PTHREAD_MUTEX_INITIALIZER
static bool	is_running = true
static pthread_t	tid
static double	voltage_now = 3.6
static double	dvoltage = 0.1
static const char	max_iv_fmt [] = "1.0000"
static bool	power_is_initialized = false
static const char	is_low_fmt [] = "0"
static bool	is_low = false
static struct statefs_slot *	is_low_slot = NULL
static struct statefs_power_prop	props []
static struct statefs_namespace	battery_ns
static struct statefs_provider	provider

Detailed Description

Example provider - provides fake power supply properties.

Provider root is provider (returned by statefs_provider_get()).

There is one namespace and array of properties. There are 3 properties: continuous voltage and current, and discrete is_low.

On first properties access separate thread is run starting to generate monotonous fake voltage values changes each second and updating is_low property when voltage value crosses "low voltage" barrier. Current (I, A) values are randomly generated. All values are formatted into fixed-size fields. Provider structures are statically defined and theoretically functionality can be taken out into framework but it was not done. Maybe later...

Access to any node is serialized by server, so power_mutex is used only to synchronize with voltage values generation thread

Function Documentation

static int power_getattr ( struct statefs_property const *  p )

static

all example properties are read-only

is_low property is discrete and this is hardcoded here and also in power_connect() and power_disconnect() for simplicity

static statefs_handle_t power_open ( struct statefs_property *  p, int  mode  )

static

Allocates power_handle structure to be used as a handle.

On first run also execute initialization of provider including starting of voltage values generation thread

static int power_read ( statefs_handle_t  h, char *  dst, statefs_size_t  len, statefs_off_t  off  )

static

if reading starting from non-zero offset it is considered read operation is continued, so previous cached result is used if exists

static statefs_ssize_t power_size ( struct statefs_property const *  p )

static

just return maximum size of the property

Variable Documentation

struct statefs_namespace battery_ns

static

Initial value:

= {
    .node = {
        .type = statefs_node_ns,
        .name = "battery",
    },
    .branch = {
        .find = prop_find,
        .first = prop_first,
        .next = prop_next,
        .get = prop_get,
    }
}

provider main (and the only) namespace

pthread_mutex_t power_mutex = PTHREAD_MUTEX_INITIALIZER

static

sync generation thread and property access

struct statefs_power_prop props[]

static

Initial value:

= {
    {
        .prop = {
            .node = {
                .type = statefs_node_prop,
                .name = "voltage"
            },
            .default_value = STATEFS_REAL(3.8)
        },
        .read = read_voltage,
        .max_size = iv_max_size
    },
    {
        .prop = {
            .node = {
                .type = statefs_node_prop,
                .name = "current"
            },
            .default_value = STATEFS_REAL(0),
        },
        .read = read_current,
        .max_size = iv_max_size
    },
    {
        .prop = {
            .node = {
                .type = statefs_node_prop,
                .name = "is_low"
            },
            .default_value = STATEFS_BOOL(false)
        },
        .read = read_is_low,
        .max_size = is_low_max_len
    }
}

array describing properties

struct statefs_provider provider

static

Initial value:

= {
    .version = STATEFS_CURRENT_VERSION,
    .root = {
        .node = {
            .type = statefs_node_root,
            .name = "power",
            .release = &power_release
        },
        .branch = {
            .find = ns_find,
            .first = &ns_first,
            .get = &ns_get
        }
    },
    
    .io = {
        .getattr = power_getattr,
        .open = power_open,
        .read = power_read,
        .size = power_size,
        .close = power_close,
        .connect = power_connect,
        .disconnect = power_disconnect
    }
}

provider root structure