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Diffstat (limited to 'Documentation/usb/ohci-hcd.txt')
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diff --git a/Documentation/usb/ohci-hcd.txt b/Documentation/usb/ohci-hcd.txt new file mode 100644 index 000000000..37a637251 --- /dev/null +++ b/Documentation/usb/ohci-hcd.txt @@ -0,0 +1,98 @@ + +The OHCI HCD layer is a simple but nearly complete implementation of what the +USB people would call a HCD for the OHCI. + (ISO comming soon, Bulk, INT u. CTRL transfers enabled) +It is based on Linus Torvalds UHCI code and Gregory Smith OHCI fragments (0.03 source tree). +The layer (functions) on top of it, is for interfacing to the alternate-usb device-drivers. + +- Roman Weissgaerber <weissg@vienna.at> + + * v4.0 1999/08/18 removed all dummy eds, unlink unused eds, code cleanup, bulk transfers + * v2.1 1999/05/09 ep_addr correction, code cleanup + * v0.2.0 1999/05/04 + * everything has been moved into 2 files (ohci-hcd.c, ohci-hub-root.c and headers) + * virtual root hub is now an option, + * memory allocation based on kmalloc and kfree now, simple Bus error handling, + * INT and CTRL transfers enabled, Bulk included but disabled, ISO needs completion + * + * from Linus Torvalds (uhci.c): APM (not tested); hub, usb_device, bus and related stuff + * from Greg Smith (ohci.c): better reset ohci-controller handling, hub + * + * v0.1.0 1999/04/27 initial release + +to remove the module try: +rmmod usb-ohci-hcd + +Features: +- virtual root hub, all basic hub descriptors and commands (state: complete) + this is an option now (v0.2.0) + #define CONFIG_USB_OHCI_VROOTHUB includes the virtual hub code, (VROOTHUB) + default is with. + (at the moment: the Virtual Root Hub is included automatically) + + files: ohci-root-hub.c, ohci-root-hub.h + + +- Endpoint Descriptor (ED) handling more static approach + (EDs should be allocated in parallel to the SET CONFIGURATION command and they live + as long as the function (device) is alive or another configuration is choosen. + In the HCD layer the EDs has to be allocated manually either by calling a subroutine + or by sending a USB root hub vendor specific command to the virtual root hub. + At the alternate linux usb stack EDs will be added (allocated) at their first use. + ED will be unlinked from the HC chains if they are not bussy. + + files: ohci-hcd.c ohci-hcd.h + routines: (do not use for drivers, use the top layer alternate usb commands instead) + + int usb_ohci_add_ep(struct ohci * ohci, unsigned int ep_addr1, + int interval, int load, f_handler handler, int ep_size, int speed) + adds an endpoint, (if the endpoint already exists some parameters will be updated) + + int usb_ohci_rm_ep( ) + removes an endpoint and all pending TDs of that EP + + usb_ohci_rm_function( ) + removes all Endpoints of a function (device) + +- Transfer Descriptors (TD): handling and allocation of TDs is transparent to the upper layers + The HCD takes care of TDs and EDs memory allocation whereas the upper layers (UBSD ...) has + to take care of buffer allocation. + files: ohci-hcd.c ohci-hcd.h + + There is one basic command for all types of bus transfers (INT, BULK, ISO, CTRL): + + int ohci_trans_req(struct ohci * ohci, hcd_ed, int ctrl_len, void *ctrl, void * data, int data_len, __OHCI_BAG lw0, __OHCI_BAG lw1) + + CTRL: ctrl, ctrl_len ... cmd buffer + data, data_len ... data buffer (in or out) + INT, BULK: ctrl = NULL, ctrl_len=0, + data, data_len ... data buffer (in or out) + ISO: tbd + + There is no buffer reinsertion done by the internal HCD function. + (The interface layer does this for a INT-pipe on request.) + If you want a transfer then you have to + provide buffers by sending ohci_trans_req requests. As they are queued as TDs on an ED + you can send as many as you like. They should come back by the callback f_handler in + the same order (for each endpoint, not globally) If an error occurs all + queued transfers of an endpoint will return unsent. They will be marked with an error status. + + e.g double-buffering for int transfers: + + ohci_trans_req(ohci, ep_addr, 0, NULL, data0, data0_len, 0,0) + ohci_trans_req(ohci, ep_addr, 0, NULL, data1, data1_len, 0,0) + + and when a data0 packet returns by the callback f_handler requeue it: + ohci_trans_req(ohci, ep_addr, 0, NULL, data0, data0_len, 0,0) + and when a data1 packet returns by the callback f_handler requeue it: + ohci_trans_req(ohci, ep_addr, 0, NULL, data1, data1_len, 0,0) + + lw0, lw1 are private fields for upper layers for ids or fine grained handlers. + The alternate usb uses them for dev_id and usb_device_irq handler. + + +- Done list handling: returns the requests (callback f_handler in ED) and does + some error handling, root-hub request dequeuing + (files: ohci-done-list.c in ohci-hcd.c now(v0.2.0)) + + |