harvey/sys/man/2/usb

.TH USB 2
.SH NAME
usbcmd,
classname,
closedev,
configdev,
devctl,
finddevs,
loaddevstr,
matchdevcsp,
opendev,
opendevdata,
openep,
startdevs,
unstall,
class,
subclass,
proto,
CSP \- USB device driver library
.SH SYNOPSIS
.EX
.ta 8n +8n +8n +8n +8n +8n +8n
#include <u.h>
#include <libc.h>
#include <thread.h>
#include "../lib/usb.h"
.sp 0.3v
struct Dev {
	Ref;
	char*	dir;		/* path for the endpoint dir */
	int	id;		/* usb id for device or ep. number */
	int	dfd;		/* descriptor for the data file */
	int	cfd;		/* descriptor for the control file */
	int	maxpkt;		/* cached from usb description */
	Usbdev*	usb;		/* USB description */
	void*	aux;		/* for the device driver */
	void	(*free)(void*);	/* idem. to release aux */
};
.sp 0.3v
struct Usbdev {
	ulong	csp;		/* USB class/subclass/proto */
	int	vid;		/* vendor id */
	int	did;		/* product (device) id */
	int	dno;		/* device release number */
	char*	vendor;
	char*	product;
	char*	serial;
	int	ls;		/* low speed */
	int	class;		/* from descriptor */
	int	nconf;		/* from descriptor */
	Conf*	conf[Nconf];	/* configurations */
	Ep*	ep[Nep];	/* all endpoints in device */
	Desc*	ddesc[Nddesc];	/* (raw) device specific descriptors */
};
.sp 0.3v
struct Ep {
	uchar	addr;		/* endpt address */
	uchar	dir;		/* direction, Ein/Eout */
	uchar	type;		/* Econtrol, Eiso, Ebulk, Eintr */
	uchar	isotype;	/* Eunknown, Easync, Eadapt, Esync */
	int	id;
	int	maxpkt;		/* max. packet size */
	Conf*	conf;		/* the endpoint belongs to */
	Iface*	iface;		/* the endpoint belongs to */
};
.sp 0.3v
struct Altc {
	int	attrib;
	int	interval;
	void*	aux;		/* for the driver program */
};
.sp 0.3v
struct Iface {
	int 	id;		/* interface number */
	ulong	csp;		/* USB class/subclass/proto */
	Altc*	altc[Naltc];
	Ep*	ep[Nep];
	void*	aux;		/* for the driver program */
};
.sp 0.3v
struct Conf {
	int	cval;		/* value for set configuration */
	int	attrib;
	int	milliamps;	/* maximum power in this config. */
	Iface*	iface[Niface];	/* up to 16 interfaces */
};
.sp 0.3v
struct Desc {
	Conf*	conf;		/* where this descriptor was read */
	Iface*	iface;		/* last iface before desc in conf. */
	Ep*	ep;		/* last endpt before desc in conf. */
	Altc*	altc;		/* last alt.c. before desc in conf. */
	DDesc	data;		/* unparsed standard USB descriptor */
};
.sp 0.3v
struct DDesc {
	uchar	bLength;
	uchar	bDescriptorType;
	uchar	bbytes[1];
	/* extra bytes allocated here to keep the rest of it */
};
.sp 0.3v
#define Class(csp)	((csp)&0xff)
#define Subclass(csp)	(((csp)>>8)&0xff)
#define Proto(csp)	(((csp)>>16)&0xff)
#define CSP(c, s, p)	((c) | ((s)<<8) | ((p)<<16))
#define	GET2(p)		...
#define	PUT2(p,v)	...
#define	GET4(p)		...
#define	PUT4(p,v)	...
#define dprint	 if(usbdebug)fprint
#define ddprint if(usbdebug > 1)fprint
.sp 0.3v
int	Ufmt(Fmt *f);
char*	classname(int c);
void	closedev(Dev *d);
int	configdev(Dev *d);
int	devctl(Dev *dev, char *fmt, ...);
void*	emallocz(ulong size, int zero);
char*	estrdup(char *s);
int	finddevs(int (*matchf)(char*,void*), void *farg, char** dirs, int ndirs);
char*	hexstr(void *a, int n);
char*	loaddevstr(Dev *d, int sid);
int	matchdevcsp(char *info, void *a);
Dev*	opendev(char *fn);
int	opendevdata(Dev *d, int mode);
Dev*	openep(Dev *d, int id);
void	startdevs(char *args, char *argv[], int argc,
		int (*mf)(char*,void*), void*ma, int (*df)(Dev*,int,char**));
int	unstall(Dev *dev, Dev *ep, int dir);
int	usbcmd(Dev *d, int type, int req,
		int value, int index, uchar *data, int count);
.sp 0.3v
extern int usbdebug;	/* more messages for bigger values */
.EE
.SH DESCRIPTION
This library provides convenience structures and functions to write
USB device drivers.
It is not intended for user programs using USB devices.
See
.IR usb (3)
for a description of the interfaces provided for that purpose.
For drivers that provide a file system and may be embedded into
.IR usbd ,
the library includes a file system implementation toolkit described in
.IR usbfs (2).
.PP
Usb drivers rely on
.IR usb (3)
to perform I/O through USB as well as on
.IR usbd (4)
to perform the initial configuration for the device's setup endpoint.
The rest of the work is up to the driver and is where this library may help.
.PP
In most cases, a driver locates the devices of interest and configures them
by calling
.I startdevs
and
then sets up additional endpoints as needed (by calling
.IR openep )
to finally perform I/O by reading and writing the
data files for the endpoints.
.PP
An endpoint as provided by
.IR usb (3)
is represented by a
.B Dev
data structure.
The setup endpoint for a
device represents the USB device, because it is the means to
configure and operate the device.
This structure is reference counted.
Functions creating
.B Devs
adjust the number of references to one, initially.
The driver is free to call
.IR incref
(in
.IR lock (2))
to add references and
.I closedev
to drop references (and release resources when the last one vanishes).
As an aid to the driver, the field
.B aux
may keep driver-specific data and the function
.B free
will be called (if not null) to release the
.B aux
structure when the reference count goes down to zero.
.PP
.I Dev.dir
holds the path for the endpoint's directory.
.PP
The field
.B id
keeps the device number for setup endpoints and the endpoint number
for all other endpoints.
For example, it would be
.B 3
for
.B /dev/usb/ep3.0
and
.B 1
for
.BR /dev/usb/ep3.1 .
It is easy to remember this because the former is created to operate
on the device, while the later has been created as a particular endpoint
to perform I/O.
.PP
Fields
.B dfd
and
.B cfd
keep the data and
control file descriptors, respectively.
When a
.B Dev
is created the control file is open, initially.
Opening the data
file requires calling
.I opendevdata
with the appropriate mode.
.PP
When the device configuration information has been loaded (see below),
.B maxpkt
holds the maximum packet size (in bytes) for the endpoint and
.B usb
keeps the rest of the USB information.
.PP
Most of the information in
.B usb
comes from parsing
various device and configuration descriptors provided by the device,
by calling one of the functions described later.
Only descriptors unknown
to the library are kept unparsed at
.B usb.ddesc
as an aid for the driver
(which should know how to parse them and what to do with the information).
.SS Configuration
.I Startdevs
is a wrapper that locates devices of interest, loads their configuration
information, and starts a
.IR thread (2)'s
.I proc
for each device located so that it executes
.I f
as its main entry point. The entry point is called with a pointer to
the
.B Dev
for the device it has to process,
.BR argc ,
and
.BR argv .
Devices are located either from the arguments (after options) in
.IR argv ,
if any,
or by calling the helper function
.I mf
with the argument
.I ma
to determine (for each device available) if the device belongs to
the driver or not. If the function returns -1 then the device is not for us.
.PP
In many cases,
.I matchdevcsp
may be supplied as
.I mf
along with a (null terminated) vector of CSP values supplied as
.IR ma .
This function returns 0 for any device with a CSP matching one in the
vector supplied as an argument and -1 otherwise.
In other cases (eg., when a particular vendor and device ids are the
ones identifying the device) the driver must include its own function
and supply it as an argument to
.IR startdevs .
The first argument of the function corresponds to the information
known about the device (the second line in its
.B ctl
file).
.I Openep
creates the endpoint number
.I id
for the device
.I d
and returns a
.B Dev
structure to operate on it (with just the control file open).
.PP
.I Opendev
creates a
.B Dev
for the endpoint with directory
.IR fn .
Usually, the endpoint is a setup endpoint representing a device. The endpoint
control file is open, but the data file is not. The USB description is void.
In most cases drivers call
.I startdevs
and
.I openep
and do not call this function directly.
.PP
.I Configdev
opens the data file for the device supplied and
loads and parses its configuration information.
After calling it, the device is ready for I/O and the USB description in
.B Dev.usb
is valid.
When using
.IR startdevs
it is not desirable to call this function (because
.IR startdevs
already calls it).
.PP
Control requests for an endpoint may be written by calling
.I devctl
in the style of
.IR print (2).
It is better not to call
.I print
directly because the control request should be issued as a single
.I write
system call.
See
.IR usb (3)
for a list of available control requests (not to be confused with
USB control transfers performed on a control endpoint).
.SS Input/Output
.I Opendevdata
opens the data file for the device according to the given
.IR mode .
The mode must match that of the endpoint, doing otherwise is considered
an error.
Actual I/O is performed by reading/writing the descriptor kept in the
.B dfd
field of
.BR Dev .
.PP
For control endpoints,
it is not necessary to call
.I read
and
.I write
directly.
Instead,
.I usbcmd
issues a USB control request to the device
.I d
(not to be confused with a
.IR usb (3)
control request sent to its control file).
.I Usbcmd
retries the control request several times upon failure because some devices
require it.
The format of requests is fixed per the USB standard:
.I type
is the type of request and
.I req
identifies the request. Arguments
.I value
and
.I index
are parameters to the request and the last two arguments,
.I data
and
.IR count ,
are similar to
.I read
and
.I write
arguments.
However,
.I data
may be
.B nil
if no transfer (other than the control request) has to take place.
The library header file includes numerous symbols defined to help writing
the type and arguments for a request.
.PP
The return value from
.I usbcmd
is the number of bytes transferred, zero to indicate a stall and -1
to indicate an error.
.PP
A common request is to unstall an endpoint that has been stalled
due to some reason by the device (eg., when read or write indicate
a count of zero bytes read or written on the endpoint). The function
.I unstall
does this.
It is given the device that stalled the endpoint,
.IR dev ,
the
stalled endpoint,
.IR ep ,
and the direction of the stall (one of
.B Ein
or
.BR Eout ).
The function takes care of notifying the device of the unstall as well
as notifying the kernel.
.SS Tools
.I Class
returns the class part of the number given, representing a CSP.
.I Subclass
does the same for the device subclass and
.I Proto
for the protocol.
The counterpart is
.IR CSP ,
which builds a CSP from the device class, subclass, and protocol.
For some classes,
.I classname
knows the name (for those with constants in the library header file).
.PP
The macros
.I GET2
and
.I PUT2
get and put a (little-endian) two-byte value and are useful to
parse descriptors and replies for control requests.
.PP
Functions
.I emallocz
and
.I estrdup
are similar to
.I mallocz
and
.I strdup
but abort program operation upon failure.
.PP
The function
.I Ufmt
is a format routine suitable for
.IR fmtinstall (2)
to print a
.B Dev
data structure.
The auxiliary
.I hexstr
returns a string representing a dump (in hexadecimal) of
.I n
bytes starting at
.IR a .
The string is allocated using
.IR malloc (2)
and memory must be released by the caller.
.PP
.I Loaddevstr
returns the string obtained by reading the device string descriptor number
.IR sid .
.SH SOURCE
.B /sys/src/cmd/usb/lib
.SH "SEE ALSO"
.IR usbfs (2),
.IR usb (3),
.IR usb (4),
.IR usbd (4).
.SH BUGS
Not heavily exercised yet.