From: Mauro Carvalho Chehab Date: Wed, 5 Apr 2017 13:23:02 +0000 (-0300) Subject: usb/anchors.txt: convert to ReST and add to driver-api book X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=79e0c2e6d4a382a7ac80cf082e3ca60bd42ab475;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git usb/anchors.txt: convert to ReST and add to driver-api book This document describe some USB core functions. Add it to the driver-api book. Signed-off-by: Mauro Carvalho Chehab Acked-by: Greg Kroah-Hartman Signed-off-by: Jonathan Corbet --- diff --git a/Documentation/driver-api/usb/anchors.rst b/Documentation/driver-api/usb/anchors.rst new file mode 100644 index 000000000000..4b248e691bd6 --- /dev/null +++ b/Documentation/driver-api/usb/anchors.rst @@ -0,0 +1,83 @@ +USB Anchors +~~~~~~~~~~~ + +What is anchor? +=============== + +A USB driver needs to support some callbacks requiring +a driver to cease all IO to an interface. To do so, a +driver has to keep track of the URBs it has submitted +to know they've all completed or to call usb_kill_urb +for them. The anchor is a data structure takes care of +keeping track of URBs and provides methods to deal with +multiple URBs. + +Allocation and Initialisation +============================= + +There's no API to allocate an anchor. It is simply declared +as struct usb_anchor. :c:func:`init_usb_anchor` must be called to +initialise the data structure. + +Deallocation +============ + +Once it has no more URBs associated with it, the anchor can be +freed with normal memory management operations. + +Association and disassociation of URBs with anchors +=================================================== + +An association of URBs to an anchor is made by an explicit +call to :c:func:`usb_anchor_urb`. The association is maintained until +an URB is finished by (successful) completion. Thus disassociation +is automatic. A function is provided to forcibly finish (kill) +all URBs associated with an anchor. +Furthermore, disassociation can be made with :c:func:`usb_unanchor_urb` + +Operations on multitudes of URBs +================================ + +:c:func:`usb_kill_anchored_urbs` +-------------------------------- + +This function kills all URBs associated with an anchor. The URBs +are called in the reverse temporal order they were submitted. +This way no data can be reordered. + +:c:func:`usb_unlink_anchored_urbs` +---------------------------------- + + +This function unlinks all URBs associated with an anchor. The URBs +are processed in the reverse temporal order they were submitted. +This is similar to :c:func:`usb_kill_anchored_urbs`, but it will not sleep. +Therefore no guarantee is made that the URBs have been unlinked when +the call returns. They may be unlinked later but will be unlinked in +finite time. + +:c:func:`usb_scuttle_anchored_urbs` +----------------------------------- + +All URBs of an anchor are unanchored en masse. + +:c:func:`usb_wait_anchor_empty_timeout` +--------------------------------------- + +This function waits for all URBs associated with an anchor to finish +or a timeout, whichever comes first. Its return value will tell you +whether the timeout was reached. + +:c:func:`usb_anchor_empty` +-------------------------- + +Returns true if no URBs are associated with an anchor. Locking +is the caller's responsibility. + +:c:func:`usb_get_from_anchor` +----------------------------- + +Returns the oldest anchored URB of an anchor. The URB is unanchored +and returned with a reference. As you may mix URBs to several +destinations in one anchor you have no guarantee the chronologically +first submitted URB is returned. diff --git a/Documentation/driver-api/usb/index.rst b/Documentation/driver-api/usb/index.rst index cf2fa2e8d236..5dfb04b2d730 100644 --- a/Documentation/driver-api/usb/index.rst +++ b/Documentation/driver-api/usb/index.rst @@ -6,6 +6,7 @@ Linux USB API usb gadget + anchors writing_usb_driver writing_musb_glue_layer diff --git a/Documentation/usb/anchors.txt b/Documentation/usb/anchors.txt deleted file mode 100644 index fe6a99a32bbd..000000000000 --- a/Documentation/usb/anchors.txt +++ /dev/null @@ -1,79 +0,0 @@ -What is anchor? -=============== - -A USB driver needs to support some callbacks requiring -a driver to cease all IO to an interface. To do so, a -driver has to keep track of the URBs it has submitted -to know they've all completed or to call usb_kill_urb -for them. The anchor is a data structure takes care of -keeping track of URBs and provides methods to deal with -multiple URBs. - -Allocation and Initialisation -============================= - -There's no API to allocate an anchor. It is simply declared -as struct usb_anchor. init_usb_anchor() must be called to -initialise the data structure. - -Deallocation -============ - -Once it has no more URBs associated with it, the anchor can be -freed with normal memory management operations. - -Association and disassociation of URBs with anchors -=================================================== - -An association of URBs to an anchor is made by an explicit -call to usb_anchor_urb(). The association is maintained until -an URB is finished by (successful) completion. Thus disassociation -is automatic. A function is provided to forcibly finish (kill) -all URBs associated with an anchor. -Furthermore, disassociation can be made with usb_unanchor_urb() - -Operations on multitudes of URBs -================================ - -usb_kill_anchored_urbs() ------------------------- - -This function kills all URBs associated with an anchor. The URBs -are called in the reverse temporal order they were submitted. -This way no data can be reordered. - -usb_unlink_anchored_urbs() --------------------------- - -This function unlinks all URBs associated with an anchor. The URBs -are processed in the reverse temporal order they were submitted. -This is similar to usb_kill_anchored_urbs(), but it will not sleep. -Therefore no guarantee is made that the URBs have been unlinked when -the call returns. They may be unlinked later but will be unlinked in -finite time. - -usb_scuttle_anchored_urbs() ---------------------------- - -All URBs of an anchor are unanchored en masse. - -usb_wait_anchor_empty_timeout() -------------------------------- - -This function waits for all URBs associated with an anchor to finish -or a timeout, whichever comes first. Its return value will tell you -whether the timeout was reached. - -usb_anchor_empty() ------------------- - -Returns true if no URBs are associated with an anchor. Locking -is the caller's responsibility. - -usb_get_from_anchor() ---------------------- - -Returns the oldest anchored URB of an anchor. The URB is unanchored -and returned with a reference. As you may mix URBs to several -destinations in one anchor you have no guarantee the chronologically -first submitted URB is returned.