| Copyright | (c) 2018 Drew Hess |
|---|---|
| License | BSD3 |
| Maintainer | Drew Hess <src@drewhess.com> |
| Stability | experimental |
| Portability | non-portable |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
System.GPIO.Linux.Sysfs.Monad
Contents
Description
Monad type classes and instances for Linux sysfs GPIO operations.
Synopsis
- class Monad m => MonadSysfs m where
- newtype PinDescriptor = PinDescriptor {}
- newtype SysfsGpioT m a = SysfsGpioT {
- runSysfsGpioT :: m a
- type CatchSysfsM m = (Functor m, MonadCatch m, MonadSysfs m)
- type ThrowSysfsM m = (Functor m, MonadThrow m, MonadSysfs m)
- type ThrowCatchSysfsM m = (Functor m, MonadThrow m, MonadCatch m, MonadSysfs m)
- sysfsIsPresent :: MonadSysfs m => m Bool
- availablePins :: ThrowCatchSysfsM m => m [Pin]
- pinIsExported :: MonadSysfs m => Pin -> m Bool
- exportPin :: CatchSysfsM m => Pin -> m ()
- exportPinChecked :: CatchSysfsM m => Pin -> m ()
- unexportPin :: CatchSysfsM m => Pin -> m ()
- unexportPinChecked :: CatchSysfsM m => Pin -> m ()
- pinHasDirection :: ThrowSysfsM m => Pin -> m Bool
- readPinDirection :: ThrowCatchSysfsM m => Pin -> m PinDirection
- writePinDirection :: CatchSysfsM m => Pin -> PinDirection -> m ()
- writePinDirectionWithValue :: CatchSysfsM m => Pin -> PinValue -> m ()
- readPinValue :: ThrowCatchSysfsM m => Pin -> m PinValue
- pollPinValue :: ThrowCatchSysfsM m => Pin -> m PinValue
- pollPinValueTimeout :: ThrowCatchSysfsM m => Pin -> Int -> m (Maybe PinValue)
- writePinValue :: CatchSysfsM m => Pin -> PinValue -> m ()
- pinHasEdge :: ThrowSysfsM m => Pin -> m Bool
- readPinEdge :: ThrowCatchSysfsM m => Pin -> m SysfsEdge
- writePinEdge :: CatchSysfsM m => Pin -> SysfsEdge -> m ()
- readPinActiveLow :: ThrowCatchSysfsM m => Pin -> m Bool
- writePinActiveLow :: CatchSysfsM m => Pin -> Bool -> m ()
MonadSysfs class
class Monad m => MonadSysfs m where Source #
A type class for monads which implement (or mock) low-level Linux
sysfs GPIO operations.
Methods
doesDirectoryExist :: FilePath -> m Bool Source #
Equivalent to doesDirectoryExist.
doesFileExist :: FilePath -> m Bool Source #
Equivalent to doesFileExist.
getDirectoryContents :: FilePath -> m [FilePath] Source #
Equivalent to getDirectoryContents.
readFile :: FilePath -> m ByteString Source #
Equivalent to readFile.
writeFile :: FilePath -> ByteString -> m () Source #
Equivalent to writeFile.
unlockedWriteFile :: FilePath -> ByteString -> m () Source #
sysfs control files which are global shared resources may be
written simultaneously by multiple threads. This is fine --
sysfs can handle this -- but Haskell's
writeFile cannot, as it locks the file and
prevents multiple writers. We don't want this behavior, so we use
low-level operations to get around it.
pollFile :: FilePath -> Int -> m CInt Source #
Poll a sysfs file for reading, as in POSIX.1-2001 poll(2).
Note that the implementation of this action is only guaranteed to
work for sysfs files, which have a peculiar way of signaling
readiness for reads. Do not use it for any other purpose.
doesDirectoryExist :: (MonadTrans t, MonadSysfs m', t m' ~ m) => FilePath -> m Bool Source #
Equivalent to doesDirectoryExist.
doesFileExist :: (MonadTrans t, MonadSysfs m', t m' ~ m) => FilePath -> m Bool Source #
Equivalent to doesFileExist.
getDirectoryContents :: (MonadTrans t, MonadSysfs m', t m' ~ m) => FilePath -> m [FilePath] Source #
Equivalent to getDirectoryContents.
readFile :: (MonadTrans t, MonadSysfs m', t m' ~ m) => FilePath -> m ByteString Source #
Equivalent to readFile.
writeFile :: (MonadTrans t, MonadSysfs m', t m' ~ m) => FilePath -> ByteString -> m () Source #
Equivalent to writeFile.
unlockedWriteFile :: (MonadTrans t, MonadSysfs m', t m' ~ m) => FilePath -> ByteString -> m () Source #
sysfs control files which are global shared resources may be
written simultaneously by multiple threads. This is fine --
sysfs can handle this -- but Haskell's
writeFile cannot, as it locks the file and
prevents multiple writers. We don't want this behavior, so we use
low-level operations to get around it.
pollFile :: (MonadTrans t, MonadSysfs m', t m' ~ m) => FilePath -> Int -> m CInt Source #
Poll a sysfs file for reading, as in POSIX.1-2001 poll(2).
Note that the implementation of this action is only guaranteed to
work for sysfs files, which have a peculiar way of signaling
readiness for reads. Do not use it for any other purpose.
Instances
GPIO via sysfs
newtype PinDescriptor Source #
The sysfs pin handle type. Currently it's just a newtype
wrapper around a Pin. The constructor is exported for
convenience, but note that the implementation may change in future
versions of the package.
Constructors
| PinDescriptor | |
Instances
newtype SysfsGpioT m a Source #
An instance of MonadGpio which translates actions in that monad
to operations on Linux's native sysfs GPIO interface.
Constructors
| SysfsGpioT | |
Fields
| |
Instances
Convenient constraint synonyms for MonadSysfs signatures.
type CatchSysfsM m = (Functor m, MonadCatch m, MonadSysfs m) Source #
type ThrowSysfsM m = (Functor m, MonadThrow m, MonadSysfs m) Source #
type ThrowCatchSysfsM m = (Functor m, MonadThrow m, MonadCatch m, MonadSysfs m) Source #
Low-level sysfs GPIO actions.
sysfsIsPresent :: MonadSysfs m => m Bool Source #
Test whether the sysfs GPIO filesystem is available.
availablePins :: ThrowCatchSysfsM m => m [Pin] Source #
Return a list of all pins that are exposed via the sysfs GPIO
filesystem. Note that the returned list may omit some pins that
are available on the host but which, for various reasons, are not
exposed via the sysfs GPIO filesystem.
pinIsExported :: MonadSysfs m => Pin -> m Bool Source #
Test whether the pin is already exported.
exportPin :: CatchSysfsM m => Pin -> m () Source #
Export the given pin.
Note that, if the pin is already exported, this is not an error; in this situation, the pin remains exported and its state unchanged.
exportPinChecked :: CatchSysfsM m => Pin -> m () Source #
Export the given pin.
Note that, unlike exportPin, it's an error to call this action to
export a pin that's already been exported. This is the standard
Linux sysfs GPIO behavior.
unexportPin :: CatchSysfsM m => Pin -> m () Source #
Unexport the given pin.
Note that, if the pin is already unexported or cannot be unexported, this is not an error. In this situation, the pin remains exported and its state unchanged.
unexportPinChecked :: CatchSysfsM m => Pin -> m () Source #
Unexport the given pin.
Note that, unlike unexportPin, it is an error to call this action
if the pin is not currently exported. This is the standard Linux
sysfs GPIO behavior.
pinHasDirection :: ThrowSysfsM m => Pin -> m Bool Source #
Test whether the pin's direction can be set via the sysfs GPIO
filesystem. (Some pins have a hard-wired direction, in which case
their direction must be determined by some other mechanism, as the
direction attribute does not exist for such pins.)
readPinDirection :: ThrowCatchSysfsM m => Pin -> m PinDirection Source #
Read the pin's direction.
It is an error to call this action if the pin has no direction
attribute.
writePinDirection :: CatchSysfsM m => Pin -> PinDirection -> m () Source #
Set the pin's direction.
It is an error to call this action if the pin has no direction
attribute.
Note that, in Linux sysfs GPIO, changing a pin's direction to
out will also set its physical signal level to low.
NB: in Linux sysfs, if an input pin is cofigured for edge- or
level-triggered reads, it's an error to set its direction to out.
However, this action will handle that case gracefully by setting
the pin's edge attribute to none before setting the pin's
direction to out.
writePinDirectionWithValue :: CatchSysfsM m => Pin -> PinValue -> m () Source #
Pins whose direction can be set may be configured for output by
writing a PinValue to their direction attribute, such that the
given value will be driven on the pin as soon as it's configured
for output. This enables glitch-free output configuration, assuming
the pin is currently configured for input, or some kind of
tri-stated or floating high-impedance mode.
It is an error to call this action if the pin has no direction
attribute.
NB: for some unfathomable reason, writing high or low to a
pin's direction attribute sets its physical signal level; i.e.,
it ignores the value of the pin's active_low attribute. Contrast
this behavior with the behavior of writing to the pin's value
attribute, which respects the value of the pin's active_low
attribute and sets the pin's logical signal level.
Rather than slavishly following the Linux sysfs GPIO spec, we
choose to be consistent by taking into account the pin's active
level when writing the direction attribute. In other words, the
PinValue argument to this action is the logical signal level
that will be set on the pin. If you're using this action to program
directly to the Linux sysfs GPIO interface and expecting things
to behave as they do with raw sysfs GPIO operations, keep this in
mind!
readPinValue :: ThrowCatchSysfsM m => Pin -> m PinValue Source #
Read the pin's signal level.
Note that this action never blocks, regardless of the pin's edge
attribute setting.
pollPinValue :: ThrowCatchSysfsM m => Pin -> m PinValue Source #
A blocking version of readPinValue. The current thread will
block until an event occurs on the pin as specified by the pin's
current edge attribute setting.
If the pin has no edge attribute, then this action's behavior is
undefined. (Most likely, it will block indefinitely.)
pollPinValueTimeout :: ThrowCatchSysfsM m => Pin -> Int -> m (Maybe PinValue) Source #
Same as pollPinValue, except that a timeout value,
specified in microseconds, is provided. If no event occurs before
the timeout expires, this action returns Nothing; otherwise, it
returns the pin's value wrapped in a Just.
If the timeout value is negative, this action behaves just like
pollPinValue.
When specifying a timeout value, be careful not to exceed
maxBound.
If the pin has no edge attribute, then this action's behavior is
undefined. (Most likely, it will time out after the specified delay
and return Nothing.)
NB: the curent implementation of this action limits the timeout precision to 1 millisecond, rather than 1 microsecond as the timeout parameter implies.
writePinValue :: CatchSysfsM m => Pin -> PinValue -> m () Source #
Set the pin's signal level.
It is an error to call this action if the pin is configured as an input pin.
pinHasEdge :: ThrowSysfsM m => Pin -> m Bool Source #
Test whether the pin has an edge attribute, i.e., whether it
can be configured for edge- or level-triggered interrupts.
readPinEdge :: ThrowCatchSysfsM m => Pin -> m SysfsEdge Source #
Read the pin's edge attribute.
It is an error to call this action when the pin has no edge
attribute.
writePinEdge :: CatchSysfsM m => Pin -> SysfsEdge -> m () Source #
Write the pin's edge attribute.
It is an error to call this action when the pin has no edge
attribute, or when the pin is configured for output.
readPinActiveLow :: ThrowCatchSysfsM m => Pin -> m Bool Source #
Read the pin's active_low attribute.
writePinActiveLow :: CatchSysfsM m => Pin -> Bool -> m () Source #
Write the pin's active_low attribute.