usb-safe-0.13: Type-safe communication with USB devices.

MaintainerBas van Dijk <v.dijk.bas@gmail.com>

System.USB.Safe

Contents

Description

This modules provides the following guarantees for working with USB devices:

  • You can't reference handles to devices that are closed. In other words: no I/O with closed handles is possible.
  • The programmer can specify the region in which devices should remain open. On exit from the region the opened devices will be closed automatically.
  • You can't reference handles to configurations that have not been set.
  • You can't reference handles to interfaces that have not been claimed.
  • Just like with devices, the programmer can specify the region in which interfaces should remain claimed. On exit from the region the claimed interfaces will be released automatically.
  • You can't reference handles to alternates that have not been set.
  • You can't reference endpoints that don't belong to a setted alternate.
  • You can't read from an endpoint with an Out transfer direction.
  • You can't write to an endpoint with an In transfer direction.

This modules makes use of a technique called Lightweight monadic regions invented by Oleg Kiselyov and Chung-chieh Shan

See: http://okmij.org/ftp/Haskell/regions.html#light-weight

This technique is implemented in the regions package of which the Control.Monad.Trans.Region module is re-exported by this module.

See the usb-safe-examples package for examples how to use this library: 

git clone https://github.com/basvandijk/usb-safe-examples

Synopsis

USB devices as scarce resources

Note that this module re-exports the Control.Monad.Trans.Region module from the regions package which allows you to run regions using runRegionT and duplicate a RegionalDeviceHandle to a parent region using dup.

module Control.Monad.Trans.Region

Regional device handles

data RegionalDeviceHandle r Source

A regional handle to an opened USB device.

A regional handle to an opened USB device can be created by applying openDevice or withDevice to the USB device you wish to open.

Note that you can also duplicate a regional device handle by applying dup to it.

Instances

openDevice :: MonadControlIO pr => Device -> RegionT s pr (RegionalDeviceHandle (RegionT s pr))Source

Open a device and obtain a regional device handle. The device is automatically closed when the region terminates.

This is a non-blocking function; no requests are sent over the bus.

Exceptions:

withDevice :: MonadControlIO pr => Device -> (forall s. RegionalDeviceHandle (RegionT s pr) -> RegionT s pr α) -> pr αSource

Convenience function which opens the device, applies the given continuation function to the resulting regional device handle and runs the resulting region.

withDeviceWhichSource

Arguments

:: forall pr α . MonadControlIO pr 
=> Ctx 
-> (DeviceDesc -> Bool)

Predicate on the device descriptor.

-> (forall s. RegionalDeviceHandle (RegionT s pr) -> RegionT s pr α)

Continuation function

-> pr α 

Convenience function which finds the first device attached to the system which satisfies the given predicate on its descriptor, then opens that device and applies the given continuation function to the resulting device handle.

Exceptions:

getDevice :: RegionalDeviceHandle r -> DeviceSource

Convenience function for retrieving the device from the given regional handle.

Getting descriptors

class GetDescriptor α desc | α -> desc, desc -> α whereSource

Methods

getDesc :: α -> descSource

Get the descriptor of a given USB entity.

Instances

Resetting devices

resetDevice :: (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> cr ()Source

Perform a USB port reset to reinitialize a device. The system will attempt to restore the previous configuration and alternate settings after the reset has completed.

Note the constraint: pr `AncestorRegion` cr. This allows this function to be executed in any child region cr of the parent region pr in which the given regional handle was created.

You can only reset a device when all computations passed to setConfig, useActiveConfig and setConfigWhich have been terminated. If you call resetDevice and such a computation is still running a SettingAlreadySet exception is thrown.

If the reset fails, the descriptors change, or the previous state cannot be restored, the device will appear to be disconnected and reconnected. This means that the device handle is no longer valid (you should close it) and rediscover the device. A NotFoundException is raised to indicate that this is the case.

TODO: Think about how to handle the implications of the the previous paragraph!

This is a blocking function which usually incurs a noticeable delay.

Exceptions:

Configurations

data Config r Source

A supported configuration of a USB device parameterized by the region r in which it was created.

Note that, just like a regional device handle, a configuration can be duplicated to a parent region using dup.

Also note that you can get the descriptor of the configuration by applying getDesc to it.

Instances

getConfigs :: RegionalDeviceHandle r -> [Config r]Source

Retrieve the supported configurations from the given regional handle.

Note that the configuration is parameterized by the same region r in which the regional handle was created. This ensures you can never use a configuration outside that region.

Setting configurations

data ConfigHandle sCfg Source

A handle to an active Config which you can get using: setConfig, useActiveConfig or setConfigWhich.

The type variable sCfg is used to ensure that you can't return this handle from these functions.

setConfigSource

Arguments

:: forall pr cr s α . (AncestorRegion pr (RegionT s cr), MonadControlIO cr) 
=> Config pr

The configuration you wish to set.

-> (forall sCfg. ConfigHandle sCfg -> RegionT s cr α)

Continuation function.

-> RegionT s cr α 

Set the active configuration for a device and then apply the given continuation function to the resulting configuration handle.

USB devices support multiple configurations of which only one can be active at any given time. When a configuration is set using setConfig, useActiveConfig or setConfigWhich no threads may set a new configuration until the computation passed to these functions terminates. If you do try to set one, a SettingAlreadySet exception will be thrown.

The operating system may or may not have already set an active configuration on the device. It is up to your application to ensure the correct configuration is selected before you attempt to claim interfaces and perform other operations. If you want to use the current active configuration: useActiveConfig.

If you call this function on a device already configured with the selected configuration, then this function will act as a lightweight device reset: it will issue a SET_CONFIGURATION request using the current configuration, causing most USB-related device state to be reset (altsetting reset to zero, endpoint halts cleared, toggles reset).

You cannot change/reset configuration if other applications or drivers have claimed interfaces.

This is a blocking function.

Exceptions:

data SettingAlreadySet Source

This exception can be thrown in:

to indicate that the device was already configured with a setting.

Constructors

SettingAlreadySet 

Instances

useActiveConfigSource

Arguments

:: forall pr cr s α . (AncestorRegion pr (RegionT s cr), MonadControlIO cr) 
=> RegionalDeviceHandle pr

Regional handle to the device from which you want to use the active configuration.

-> (forall sCfg. ConfigHandle sCfg -> RegionT s cr α)

Continuation function

-> RegionT s cr α 

Apply the given continuation function to the configuration handle of the current active configuration of the given device handle.

This function needs to determine the current active configuration. This information may be cached by the operating system. If it isn't cached this function will block while a control transfer is submitted to retrieve the information.

Exceptions:

data NoActiveConfig Source

This exception can be thrown in useActiveConfig to indicate that the device is currently not configured.

Constructors

NoActiveConfig 

Instances

setConfigWhichSource

Arguments

:: forall pr cr s α . (AncestorRegion pr (RegionT s cr), MonadControlIO cr) 
=> RegionalDeviceHandle pr

Regional handle to the device for which you want to set a configuration.

-> (ConfigDesc -> Bool)

Predicate on the configuration descriptor.

-> (forall sCfg. ConfigHandle sCfg -> RegionT s cr α)

Continuation function.

-> RegionT s cr α 

Convenience function which finds the first configuration of the given device handle which satisfies the given predicate on its descriptor, then sets that configuration and applies the given function to the resulting configuration handle.

This function calls setConfig so do see its documentation.

Exceptions:

Interfaces

data Interface sCfg Source

A supported interface of a configuration which you can retrieve using getInterfaces.

To retrieve the Interface descriptors of an interface use getDesc.

Instances

getInterfaces :: ConfigHandle sCfg -> [Interface sCfg]Source

Retrieve the supported interfaces from the configuration handle.

Note that the interface is parameterized by the sCfg of the configuration handle it is derived from. This ensures that it can never be returned from the functions that created this configuration handle: setConfig, useActiveConfig and setConfigWhich.

The latter is useful because outside those functions the active configuration may change. If at that moment you still have an interface of the old configuration claiming it would be an error.

Claiming interfaces

data RegionalInterfaceHandle sCfg r Source

A regional handle to a claimed interface.

A regional handle to a claimed interface can be created by applying claim or withInterface to the interface you wish to claim.

Instances

claimSource

Arguments

:: forall pr sCfg s . MonadControlIO pr 
=> Interface sCfg

Interface you wish to claim

-> RegionT s pr (RegionalInterfaceHandle sCfg (RegionT s pr)) 

Claim the given interface in the region. When the region terminates the interface is released automatically.

Note that it is allowed to claim an already-claimed interface.

Claiming of interfaces is a purely logical operation; it does not cause any requests to be sent over the bus. Interface claiming is used to instruct the underlying operating system that your application wishes to take ownership of the interface.

This is a non-blocking function.

Exceptions:

withInterfaceSource

Arguments

:: forall pr sCfg α . MonadControlIO pr 
=> Interface sCfg

The interface you wish to claim.

-> (forall s. RegionalInterfaceHandle sCfg (RegionT s pr) -> RegionT s pr α)

Continuation function.

-> pr α 

withInterfaceWhichSource

Arguments

:: forall pr sCfg α . MonadControlIO pr 
=> ConfigHandle sCfg

Handle to a configuration of which you want to claim an interface.

-> (Interface -> Bool)

Predicate on the interface descriptors.

-> (forall s. RegionalInterfaceHandle sCfg (RegionT s pr) -> RegionT s pr α)

Continuation function.

-> pr α 

Convenience function which finds the first interface of the given configuration handle which satisfies the given predicate on its descriptors, then claims that interfaces and applies the given continuation function to the resulting regional handle.

Exceptions:

Alternates

data Alternate sCfg r Source

A supported Interface alternate setting which you can retrieve using getAlternates.

Instances

getAlternates :: RegionalInterfaceHandle sCfg r -> [Alternate sCfg r]Source

Retrieve the supported alternate settings from the given interface handle.

Note that the alternate setting is parameterized by the same type variables as the interface handle. This ensures you can never use an alternate setting outside the region in which the interface handle was created.

Setting alternates

data AlternateHandle sAlt r Source

A handle to a setted alternate setting.

You get a handle to an alternate using setAlternate, useActiveAlternate or setAlternateWhich.

The type variable sAlt is used to ensure that you can't return this handle from these functions.

setAlternateSource

Arguments

:: forall pr cr s sCfg α . (AncestorRegion pr (RegionT s cr), MonadControlIO cr) 
=> Alternate sCfg pr

The alternate you wish to set.

-> (forall sAlt. AlternateHandle sAlt pr -> RegionT s cr α)

Continuation function.

-> RegionT s cr α 

Activate an alternate setting for an interface and then apply the given continuation function to the resulting alternate handle.

Simillary to configurations, interfaces support multiple alternate settings of which only one can be active at any given time. When an alternate is set using setAlternate, useActiveAlternate or setAlternateWhich no threads may set a new alternate until the computation passed to these functions terminates. If you do try to set one a SettingAlreadySet exception will be thrown.

The operating system has always set an interface in one of the available alternates. If you want to use the current active alternate: useActiveAlternate.

This is a blocking function.

Exceptions:

useActiveAlternateSource

Arguments

:: forall pr cr s sCfg α . (AncestorRegion pr (RegionT s cr), MonadControlIO cr) 
=> RegionalInterfaceHandle sCfg pr

Regional handle to the interface from which you want to use the active alternate.

-> (forall sAlt. AlternateHandle sAlt pr -> RegionT s cr α)

Continuation function.

-> RegionT s cr α 

Apply the given function to the alternate handle of the current active alternate of the given interface handle.

To determine the current active alternate this function will block while a control transfer is submitted to retrieve the information.

Note that unlike configurations an interface is always set in one of the available alternates, so unlike useActiveConfig this function will never throw an exception like NoActiveConfig.

Exceptions:

setAlternateWhichSource

Arguments

:: forall pr cr sCfg s α . (AncestorRegion pr (RegionT s cr), MonadControlIO cr) 
=> RegionalInterfaceHandle sCfg pr

Regional handle to the interface for which you want to set an alternate.

-> (InterfaceDesc -> Bool)

Predicate on the interface descriptor.

-> (forall sAlt. AlternateHandle sAlt pr -> RegionT s cr α)

Continuation function

-> RegionT s cr α 

Convenience function which finds the first alternate of the given interface handle which satisfies the given predicate on its descriptor, then sets that alternate and applies the given function to the resulting alternate handle.

This function calls setAlternate so do see its documentation.

Exceptions:

Endpoints

data Endpoint transDir transType sAlt r Source

I/O operations on endpoints are type-safe. You can only read from an endpoint with an In transfer direction and you can only write to an endpoint with an Out transfer direction.

Reading and writing also have different implementations for the different endpoint transfer types like: Bulk and Interrupt. I/O with endpoints of other transfer types like Control and Isochronous is not possible.

This type lifts the transfer direction and transfer type information to the type-level so that I/O operations like readEndpoint and writeEndpoint can specify which endpoints they support.

You can retrieve the endpoints of an alternate using getEndpoints.

Instances

GetDescriptor (Endpoint transDir transType sAlt r) EndpointDesc 

getEndpointsSource

Arguments

:: forall transDir transType sAlt r .  
=> AlternateHandle sAlt r

Handle to the alternate from which you want to retrieve its endpoints.

-> TransferDirection transDir

Filter all endpoints which have this transfer direction.

-> TransferType transType

Filter all endpoints which have this transfer type.

-> [Endpoint transDir transType sAlt r] 

Retrieve all the endpoints from the given alternate handle which are of the given transfer direction and transfer type.

getEndpoints' :: forall transDir transType sAlt r. MkTransferDirection transDir => MkTransferType transType => AlternateHandle sAlt r -> [Endpoint transDir transType sAlt r]Source

Similar to getEndpoints but will retrieve the endpoints based on the inferred type of transfer direction and transfer type.

Note that: getEndpoints' altHndl = getEndpoints altHndl mkTransferDirection mkTransferType.

Transfer directions

data TransferDirection transDir whereSource

Constructors

Out :: TransferDirection Out 
In :: TransferDirection In 

data Out Source

Out transfer direction (host -> device) used for writing.

Instances

data In Source

In transfer direction (device -> host) used for reading.

Instances

class MkTransferDirection transDir whereSource

Methods

mkTransferDirection :: TransferDirection transDirSource

An overloaded constructor function for transfer directions.

Instances

Transfer types

data TransferType transType whereSource

Constructors

Control :: TransferType Control 
Isochronous :: TransferType Isochronous 
Bulk :: TransferType Bulk 
Interrupt :: TransferType Interrupt 

data Control Source

Instances

data Isochronous Source

Instances

data Bulk Source

Instances

data Interrupt Source

Instances

class MkTransferType transType whereSource

Methods

mkTransferType :: TransferType transTypeSource

An overloaded constructor function for transfer types.

Instances

Endpoint I/O

clearHalt :: (AncestorRegion pr cr, MonadIO cr) => Endpoint transDir transType sAlt pr -> cr ()Source

Clear the halt/stall condition for an endpoint.

Endpoints with halt status are unable to receive or transmit data until the halt condition is stalled.

You should cancel all pending transfers before attempting to clear the halt condition.

This is a blocking function.

Exceptions:

type ReadAction r = Size -> Timeout -> r (ByteString, Status)Source

Handy type synonym for read transfers.

A ReadAction is a function which takes a size which defines how many bytes to read and a timeout. The function returns an action which, when executed, performs the actual read and returns the bytestring that was read paired with an indication if the transfer timed out.

type WriteAction r = ByteString -> Timeout -> r (Size, Status)Source

Handy type synonym for write transfers.

A WriteAction is a function which takes the bytestring to write and a timeout. The function returns an action which, when exectued, returns the number of bytes that were actually written paired with an indication if the transfer timed out.

Bulk and interrupt transfers

class ReadEndpoint transType whereSource

Class of transfer types that support reading.

Methods

readEndpoint :: (AncestorRegion pr cr, MonadIO cr) => Endpoint In transType sAlt pr -> ReadAction crSource

Read bytes from an In endpoint with either a Bulk or Interrupt transfer type.

Exceptions:

Instances

class WriteEndpoint transType whereSource

Class of transfer types that support writing

Methods

writeEndpoint :: (AncestorRegion pr cr, MonadIO cr) => Endpoint Out transType sAlt pr -> WriteAction crSource

Write bytes to an Out endpoint with either a Bulk or Interrupt transfer type.

Exceptions:

Instances

class EnumReadEndpoint transType whereSource

Class of transfer types that support enumeration.

Methods

enumReadEndpointSource

Arguments

:: (AncestorRegion pr cr, MonadControlIO cr, ReadableChunk s Word8, NullPoint s) 
=> Endpoint In transType sAlt pr 
-> Size

Chunk size. A good value for this would be the maxPacketSize . endpointMaxPacketSize.

-> Timeout

Timeout (in milliseconds) that this function should wait for each chunk before giving up due to no response being received. For no timeout, use value 0.

-> Enumerator s cr α 

An enumerator for an In endpoint with either a Bulk or Interrupt transfer type.

Instances

Isochronous transfers

WARNING: You need to enable the threaded runtime (-threaded) when using the isochronous functions. They throw a runtime error otherwise!

readIsochronousEndpointSource

Arguments

:: (AncestorRegion pr cr, MonadIO cr) 
=> Endpoint In Isochronous sAlt pr 
-> [Size]

Sizes of isochronous packets

-> Timeout 
-> cr [ByteString] 

Perform a USB isochronous read.

WARNING: You need to enable the threaded runtime (-threaded) for this function to work correctly. It throws a runtime error otherwise!

Exceptions:

writeIsochronousEndpointSource

Arguments

:: (AncestorRegion pr cr, MonadIO cr) 
=> Endpoint Out Isochronous sAlt pr 
-> [ByteString]

Sizes of isochronous packets

-> Timeout 
-> cr [Size] 

Perform a USB isochronous write.

WARNING: You need to enable the threaded runtime (-threaded) for this function to work correctly. It throws a runtime error otherwise!

Exceptions:

enumReadIsochronousEndpoint :: forall s pr cr sAlt α. (ReadableChunk s Word8, AncestorRegion pr cr, MonadControlIO cr) => Endpoint In Isochronous sAlt pr -> [Size] -> Timeout -> Enumerator [s] cr αSource

Iteratee enumerator for reading isochronous endpoints.

WARNING: You need to enable the threaded runtime (-threaded) for this function to work correctly. It throws a runtime error otherwise!

Control transfers

type ControlAction α = RequestType -> Recipient -> Request -> Value -> Index -> αSource

Handy type synonym that names the parameters of a control transfer.

data RequestType Source

Control transfers can have three request types: Standard, Class and Vendor. We disallow Standard requests however because with them you can destroy the safety guarantees that this module provides.

Constructors

Class 
Vendor 

control :: forall pr cr. (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> ControlAction (Timeout -> cr ())Source

Perform a USB control request that does not transfer data.

Exceptions:

readControl :: forall pr cr. (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> ControlAction (ReadAction cr)Source

Perform a USB control read.

Exceptions:

readControlExact :: forall pr cr. (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> ControlAction (ReadExactAction cr)Source

A convenience function similar to readControl which checks if the specified number of bytes to read were actually read. Throws an IOException if this is not the case.

writeControl :: forall pr cr. (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> ControlAction (WriteAction cr)Source

Perform a USB control write.

Exceptions:

writeControlExact :: forall pr cr. (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> ControlAction (WriteExactAction cr)Source

A convenience function similar to writeControl which checks if the given bytes were actually fully written. Throws an incompleteWriteException if this is not the case.

String descriptors

getLanguages :: (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> cr [LangId]Source

Retrieve a list of supported languages.

This function may throw USBExceptions.

getStrDescSource

Arguments

:: (AncestorRegion pr cr, MonadIO cr) 
=> RegionalDeviceHandle pr 
-> StrIx 
-> LangId 
-> Int

Maximum number of characters in the requested string. An IOException will be thrown when the requested string is larger than this number.

-> cr Text 

Retrieve a string descriptor from a device.

This function may throw USBExceptions.

TODO: The following can be made more type-safe!

When I call getStrDesc I would like the type system to guarantee that the given StrIx and LangId actually belong to the given Handle. In other words I would like to get a type error when they are some arbitrary number or come from another device.

getStrDescFirstLangSource

Arguments

:: (AncestorRegion pr cr, MonadIO cr) 
=> RegionalDeviceHandle pr 
-> StrIx 
-> Int

Maximum number of characters in the requested string. An IOException will be thrown when the requested string is larger than this number.

-> cr Text 

Retrieve a string descriptor from a device using the first supported language.

This function may throw USBExceptions.

USB kernel drivers

kernelDriverActive :: (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> InterfaceNumber -> cr BoolSource

Determine if a kernel driver is active on an interface.

If a kernel driver is active, you cannot claim the interface, and libusb will be unable to perform I/O.

Exceptions:

detachKernelDriver :: (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> InterfaceNumber -> cr ()Source

Detach a kernel driver from an interface.

If successful, you will then be able to claim the interface and perform I/O.

Exceptions:

attachKernelDriver :: (AncestorRegion pr cr, MonadIO cr) => RegionalDeviceHandle pr -> InterfaceNumber -> cr ()Source

Re-attach an interface's kernel driver, which was previously detached using detachKernelDriver.

Exceptions:

withDetachedKernelDriver :: (AncestorRegion pr (RegionT s cr), MonadControlIO cr) => RegionalDeviceHandle pr -> InterfaceNumber -> RegionT s cr α -> RegionT s cr αSource

If a kernel driver is active on the specified interface the driver is detached and the given action is executed. If the action terminates, whether by normal termination or by raising an exception, the kernel driver is attached again. If a kernel driver is not active on the specified interface the action is just executed.

Exceptions: