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Merge from eCos master repository on 2001-10-02-17:59:22-BST
author jlarmour
date Tue, 02 Oct 2001 18:28:24 +0000
parents 25e238959bae
children e0c0827131d1
line wrap: on
line diff
--- a/packages/io/usb/slave/current/doc/usbs-devtab.html
+++ b/packages/io/usb/slave/current/doc/usbs-devtab.html
@@ -2,20 +2,22 @@
 <!-- This material may be distributed only subject to the terms      -->
 <!-- and conditions set forth in the Open Publication License, v1.0  -->
 <!-- or later (the latest version is presently available at          -->
-<!-- http://www.opencontent.org/openpub/)                            -->
+<!-- http://www.opencontent.org/openpub/).                           -->
 <!-- Distribution of substantively modified versions of this         -->
 <!-- document is prohibited without the explicit permission of the   -->
 <!-- copyright holder.                                               -->
 <!-- Distribution of the work or derivative of the work in any       -->
 <!-- standard (paper) book form is prohibited unless prior           -->
-<!-- permission obtained from the copyright holder                   -->
-<HTML>
-<HEAD>
-<TITLE>
-Devtab Entries</TITLE>
+<!-- permission is obtained from the copyright holder.               -->
+<HTML
+><HEAD
+><TITLE
+>Devtab Entries</TITLE
+><meta name="MSSmartTagsPreventParsing" content="TRUE">
 <META
 NAME="GENERATOR"
-CONTENT="Modular DocBook HTML Stylesheet Version 1.54"><LINK
+CONTENT="Modular DocBook HTML Stylesheet Version 1.64
+"><LINK
 REL="HOME"
 TITLE="eCos USB Slave Support"
 HREF="io-usb-slave.html"><LINK
@@ -24,173 +26,173 @@ TITLE="Starting up a USB Device"
 HREF="usbs-start.html"><LINK
 REL="NEXT"
 TITLE="Receiving Data from the Host"
-HREF="usbs-start-rx.html"></HEAD>
-<BODY
+HREF="usbs-start-rx.html"></HEAD
+><BODY
 CLASS="REFENTRY"
 BGCOLOR="#FFFFFF"
 TEXT="#000000"
 LINK="#0000FF"
 VLINK="#840084"
-ALINK="#0000FF">
-<DIV
-CLASS="NAVHEADER">
-<TABLE
+ALINK="#0000FF"
+><DIV
+CLASS="NAVHEADER"
+><TABLE
 WIDTH="100%"
 BORDER="0"
 CELLPADDING="0"
-CELLSPACING="0">
-<TR>
-<TH
+CELLSPACING="0"
+><TR
+><TH
 COLSPAN="3"
-ALIGN="center">
-eCos USB Slave Support</TH>
-</TR>
-<TR>
-<TD
+ALIGN="center"
+>eCos USB Slave Support</TH
+></TR
+><TR
+><TD
 WIDTH="10%"
 ALIGN="left"
-VALIGN="bottom">
-<A
-HREF="usbs-start.html">
-Prev</A>
-</TD>
-<TD
+VALIGN="bottom"
+><A
+HREF="usbs-start.html"
+>Prev</A
+></TD
+><TD
 WIDTH="80%"
 ALIGN="center"
-VALIGN="bottom">
-</TD>
-<TD
+VALIGN="bottom"
+></TD
+><TD
 WIDTH="10%"
 ALIGN="right"
-VALIGN="bottom">
-<A
-HREF="usbs-start-rx.html">
-Next</A>
-</TD>
-</TR>
-</TABLE>
-<HR
+VALIGN="bottom"
+><A
+HREF="usbs-start-rx.html"
+>Next</A
+></TD
+></TR
+></TABLE
+><HR
 ALIGN="LEFT"
-WIDTH="100%"></DIV>
-<H1>
-<A
-NAME="USBS-DEVTAB">
-Devtab Entries</A>
-</H1>
-<DIV
-CLASS="REFNAMEDIV">
-<A
-NAME="AEN200">
-</A>
-<H2>
-Name</H2>
-Devtab Entries&nbsp;--&nbsp;Data endpoint data structure</DIV>
-<DIV
-CLASS="REFSYNOPSISDIV">
-<A
-NAME="AEN203">
-</A>
-<H2>
-Synopsis</H2>
-<TABLE
+WIDTH="100%"></DIV
+><H1
+><A
+NAME="USBS-DEVTAB"
+>Devtab Entries</A
+></H1
+><DIV
+CLASS="REFNAMEDIV"
+><A
+NAME="AEN200"
+></A
+><H2
+>Name</H2
+>Devtab Entries&nbsp;--&nbsp;Data endpoint data structure</DIV
+><DIV
+CLASS="REFSYNOPSISDIV"
+><A
+NAME="AEN203"
+></A
+><H2
+>Synopsis</H2
+><TABLE
 BORDER="0"
 BGCOLOR="#E0E0E0"
-WIDTH="100%">
-<TR>
-<TD>
-<PRE
-CLASS="SYNOPSIS">
-/dev/usb0c
+WIDTH="100%"
+><TR
+><TD
+><PRE
+CLASS="SYNOPSIS"
+>/dev/usb0c
 /dev/usb1r
-/dev/usb2w</PRE>
-</TD>
-</TR>
-</TABLE>
-</DIV>
-<DIV
-CLASS="REFSECT1">
-<A
-NAME="AEN205">
-</A>
-<H2>
-Devtab Entries</H2>
-<P>
-USB device drivers provide two ways of transferring data between host
+/dev/usb2w</PRE
+></TD
+></TR
+></TABLE
+></DIV
+><DIV
+CLASS="REFSECT1"
+><A
+NAME="AEN205"
+></A
+><H2
+>Devtab Entries</H2
+><P
+>USB device drivers provide two ways of transferring data between host
 and peripheral. The first involves USB-specific functionality such as
 <A
-HREF="usbs-start-rx.html">
-<TT
-CLASS="FUNCTION">
-usbs_start_rx_buffer</TT>
-</A>
-.
+HREF="usbs-start-rx.html"
+><TT
+CLASS="FUNCTION"
+>usbs_start_rx_buffer</TT
+></A
+>.
 This provides non-blocking I/O: a transfer is started, and some time
 later the device driver will call a supplied completion function. The
 second uses the conventional I/O model: there are entries in the
 device table corresponding to the various endpoints. Standard calls
 such as <TT
-CLASS="FUNCTION">
-open</TT>
- can then be used to get a suitable
+CLASS="FUNCTION"
+>open</TT
+> can then be used to get a suitable
 handle. Actual I/O happens via blocking <TT
-CLASS="FUNCTION">
-read</TT>
- and
+CLASS="FUNCTION"
+>read</TT
+> and
 <TT
-CLASS="FUNCTION">
-write</TT>
- calls. In practice the blocking operations
+CLASS="FUNCTION"
+>write</TT
+> calls. In practice the blocking operations
 are simply implemented using the underlying non-blocking
-functionality.</P>
-<P>
-Each endpoint will have its own devtab entry. The exact names are
+functionality.</P
+><P
+>Each endpoint will have its own devtab entry. The exact names are
 controlled by the device driver package, but typically the root will
 be <TT
-CLASS="LITERAL">
-/dev/usb</TT>
-. This is followed by one or more
+CLASS="LITERAL"
+>/dev/usb</TT
+>. This is followed by one or more
 decimal digits giving the endpoint number, followed by
 <TT
-CLASS="LITERAL">
-c</TT>
- for a control endpoint, <TT
-CLASS="LITERAL">
-r</TT>
- for
+CLASS="LITERAL"
+>c</TT
+> for a control endpoint, <TT
+CLASS="LITERAL"
+>r</TT
+> for
 a receive endpoint (host to peripheral), and <TT
-CLASS="LITERAL">
-w</TT>
- for
+CLASS="LITERAL"
+>w</TT
+> for
 a transmit endpoint (peripheral to host). If the target hardware
 involves more than one USB device then different roots should be used,
 for example <TT
-CLASS="LITERAL">
-/dev/usb0c</TT>
- and
+CLASS="LITERAL"
+>/dev/usb0c</TT
+> and
 <TT
-CLASS="LITERAL">
-/dev/usb1_0c</TT>
-. This may require explicit
+CLASS="LITERAL"
+>/dev/usb1_0c</TT
+>. This may require explicit
 manipulation of device driver configuration options by the application
-developer.</P>
-<P>
-At present the devtab entry for a control endpoint does not support
-any I/O operations. </P>
-<DIV
-CLASS="REFSECT2">
-<A
-NAME="AEN221">
-</A>
-<H3>
-<TT
-CLASS="FUNCTION">
-write</TT>
- operations</H3>
-<P>
-<TT
-CLASS="FUNCTION">
-cyg_io_write</TT>
- and similar functions in
+developer.</P
+><P
+>At present the devtab entry for a control endpoint does not support
+any I/O operations. </P
+><DIV
+CLASS="REFSECT2"
+><A
+NAME="AEN221"
+></A
+><H3
+><TT
+CLASS="FUNCTION"
+>write</TT
+> operations</H3
+><P
+><TT
+CLASS="FUNCTION"
+>cyg_io_write</TT
+> and similar functions in
 higher-level packages can be used to perform a transfer from
 peripheral to host. Successive write operations will not be coalesced.
 For example, when doing a 1000 byte write to an endpoint that uses the
@@ -198,213 +200,213 @@ bulk transfer protocol this will involve
 and a terminating 40-byte packet. USB device drivers are not expected
 to do any locking, and if higher-level code performs multiple
 concurrent write operations on a single endpoint then the resulting
-behaviour is undefined.</P>
-<P>
-A USB <TT
-CLASS="FUNCTION">
-write</TT>
- operation will never transfer less
+behaviour is undefined.</P
+><P
+>A USB <TT
+CLASS="FUNCTION"
+>write</TT
+> operation will never transfer less
 data than specified. It is the responsibility of higher-level code to
 ensure that the amount of data being transferred is acceptable to the
 host-side code. Usually this will be defined by a higher-level
 protocol. If an attempt is made to transfer more data than the host
-expects then the resulting behaviour is undefined.</P>
-<P>
-There are two likely error conditions. <TT
-CLASS="LITERAL">
-EPIPE</TT>
-
+expects then the resulting behaviour is undefined.</P
+><P
+>There are two likely error conditions. <TT
+CLASS="LITERAL"
+>EPIPE</TT
+>
 indicates that the connection between host and target has been broken.
 <TT
-CLASS="LITERAL">
-EAGAIN</TT>
- indicates that the endpoint has been
+CLASS="LITERAL"
+>EAGAIN</TT
+> indicates that the endpoint has been
 stalled, either at the request of the host or by other activity
-inside the peripheral.</P>
-</DIV>
-<DIV
-CLASS="REFSECT2">
-<A
-NAME="AEN231">
-</A>
-<H3>
-<TT
-CLASS="FUNCTION">
-read</TT>
- operations</H3>
-<P>
-<TT
-CLASS="FUNCTION">
-cyg_io_read</TT>
- and similar functions in higher-level
+inside the peripheral.</P
+></DIV
+><DIV
+CLASS="REFSECT2"
+><A
+NAME="AEN231"
+></A
+><H3
+><TT
+CLASS="FUNCTION"
+>read</TT
+> operations</H3
+><P
+><TT
+CLASS="FUNCTION"
+>cyg_io_read</TT
+> and similar functions in higher-level
 packages can be used to perform a transfer from host to peripheral.
 This should be a complete transfer: higher-level protocols should
 define an upper bound on the amount of data being transferred, and the
 <TT
-CLASS="FUNCTION">
-read</TT>
- operation should involve at least this
+CLASS="FUNCTION"
+>read</TT
+> operation should involve at least this
 amount of data. The return value will indicate the actual transfer
-size, which may be less than requested.</P>
-<P>
-Some device drivers may support partial reads, but USB device drivers
+size, which may be less than requested.</P
+><P
+>Some device drivers may support partial reads, but USB device drivers
 are not expected to perform any buffering because that involves both
 memory and code overheads. One technique that may work for bulk
 transfers is to exploit the fact that such transfers happen in 64-byte
 packets. It is possible to <TT
-CLASS="FUNCTION">
-read</TT>
- an initial 64
+CLASS="FUNCTION"
+>read</TT
+> an initial 64
 bytes, corresponding to the first packet in the transfer. These 64
 bytes can then be examined to determine the total transfer size, and
 the remaining data can be transferred in another
 <TT
-CLASS="FUNCTION">
-read</TT>
- operation. This technique is not guaranteed
+CLASS="FUNCTION"
+>read</TT
+> operation. This technique is not guaranteed
 to work with all USB hardware. Also, if the delay between accepting
 the first packet and the remainder of the transfer is excessive then
 this could cause timeout problems for the host-side software. For
-these reasons the use of partial reads should be avoided.</P>
-<P>
-There are two likely error conditions. <TT
-CLASS="LITERAL">
-EPIPE</TT>
-
+these reasons the use of partial reads should be avoided.</P
+><P
+>There are two likely error conditions. <TT
+CLASS="LITERAL"
+>EPIPE</TT
+>
 indicates that the connection between host and target has been broken.
 <TT
-CLASS="LITERAL">
-EAGAIN</TT>
- indicates that the endpoint has been
+CLASS="LITERAL"
+>EAGAIN</TT
+> indicates that the endpoint has been
 stalled, either at the request of the host or by other activity
-inside the peripheral.</P>
-<P>
-USB device drivers are not expected to do any locking. If higher-level
+inside the peripheral.</P
+><P
+>USB device drivers are not expected to do any locking. If higher-level
 code performs multiple concurrent read operations on a single endpoint
-then the resulting behaviour is undefined.</P>
-</DIV>
-<DIV
-CLASS="REFSECT2">
-<A
-NAME="AEN244">
-</A>
-<H3>
+then the resulting behaviour is undefined.</P
+></DIV
+><DIV
+CLASS="REFSECT2"
+><A
+NAME="AEN244"
+></A
+><H3
+><TT
+CLASS="FUNCTION"
+>select</TT
+> operations</H3
+><P
+>Typical USB device drivers will not provide any support for
 <TT
-CLASS="FUNCTION">
-select</TT>
- operations</H3>
-<P>
-Typical USB device drivers will not provide any support for
-<TT
-CLASS="FUNCTION">
-select</TT>
-. Consider bulk transfers from the host to
+CLASS="FUNCTION"
+>select</TT
+>. Consider bulk transfers from the host to
 the peripheral. At the USB device driver level there is no way of
 knowing in advance how large a transfer will be, so it is not feasible
 for the device driver to buffer the entire transfer. It may be
 possible to buffer part of the transfer, for example the first 64-byte
 packet, and copy this into application space at the start of a
 <TT
-CLASS="FUNCTION">
-read</TT>
-, but this adds code and memory overheads.
+CLASS="FUNCTION"
+>read</TT
+>, but this adds code and memory overheads.
 Worse, it means that there is an unknown but potentially long delay
 between a peripheral accepting the first packet of a transfer and the
 remaining packets, which could confuse or upset the host-side
-software.</P>
-<P>
-With some USB hardware it may be possible for the device driver to
+software.</P
+><P
+>With some USB hardware it may be possible for the device driver to
 detect OUT tokens from the host without actually accepting the data,
 and this would indicate that a  <TT
-CLASS="FUNCTION">
-read</TT>
- is likely to
+CLASS="FUNCTION"
+>read</TT
+> is likely to
 succeed. However, it would not be reliable since the host-side I/O
 operation could time out. A similar mechanism could be used to
 implement <TT
-CLASS="FUNCTION">
-select</TT>
- for outgoing data, but again
-this would not be reliable.</P>
-<P>
-Some device drivers may provide partial support for
+CLASS="FUNCTION"
+>select</TT
+> for outgoing data, but again
+this would not be reliable.</P
+><P
+>Some device drivers may provide partial support for
 <TT
-CLASS="FUNCTION">
-select</TT>
- anyway, possibly under the control of a
+CLASS="FUNCTION"
+>select</TT
+> anyway, possibly under the control of a
 configuration option. The device driver's documentation should be
 consulted for further information. It is also worth noting that the
 USB-specific non-blocking API can often be used as an alternative to
 <TT
-CLASS="FUNCTION">
-select</TT>
-.</P>
-</DIV>
-<DIV
-CLASS="REFSECT2">
-<A
-NAME="AEN256">
-</A>
-<H3>
-<TT
-CLASS="FUNCTION">
-get_config</TT>
- and
+CLASS="FUNCTION"
+>select</TT
+>.</P
+></DIV
+><DIV
+CLASS="REFSECT2"
+><A
+NAME="AEN256"
+></A
+><H3
+><TT
+CLASS="FUNCTION"
+>get_config</TT
+> and
 <TT
-CLASS="FUNCTION">
-set_config</TT>
- operations</H3>
-<P>
-There are no <TT
-CLASS="FUNCTION">
-set_config</TT>
- or
+CLASS="FUNCTION"
+>set_config</TT
+> operations</H3
+><P
+>There are no <TT
+CLASS="FUNCTION"
+>set_config</TT
+> or
 <TT
-CLASS="FUNCTION">
-get_config</TT>
- (also known as
+CLASS="FUNCTION"
+>get_config</TT
+> (also known as
 <TT
-CLASS="FUNCTION">
-ioctl</TT>
-) operations defined for USB devices.
-Some device drivers may provide hardware-specific facilities this way. </P>
-<DIV
-CLASS="NOTE">
-<BLOCKQUOTE
-CLASS="NOTE">
-<P>
-<B>
-Note: </B>
-Currently the USB-specific functions related to <A
-HREF="usbs-halt.html">
-halted endpoints</A>
- cannot be accessed readily
+CLASS="FUNCTION"
+>ioctl</TT
+>) operations defined for USB devices.
+Some device drivers may provide hardware-specific facilities this way. </P
+><DIV
+CLASS="NOTE"
+><BLOCKQUOTE
+CLASS="NOTE"
+><P
+><B
+>Note: </B
+>Currently the USB-specific functions related to <A
+HREF="usbs-halt.html"
+>halted endpoints</A
+> cannot be accessed readily
 via devtab entries. This functionality should probably be made
 available via <TT
-CLASS="FUNCTION">
-set_config</TT>
- and
+CLASS="FUNCTION"
+>set_config</TT
+> and
 <TT
-CLASS="FUNCTION">
-get_config</TT>
-. It may also prove useful to provide
+CLASS="FUNCTION"
+>get_config</TT
+>. It may also prove useful to provide
 a <TT
-CLASS="FUNCTION">
-get_config</TT>
- operation that maps from the
-devtab entries to the underlying endpoint data structures.</P>
-</BLOCKQUOTE>
-</DIV>
-</DIV>
-<DIV
-CLASS="REFSECT2">
-<A
-NAME="AEN270">
-</A>
-<H3>
-Presence</H3>
-<P>
-The devtab entries are optional. If the USB device is accessed
+CLASS="FUNCTION"
+>get_config</TT
+> operation that maps from the
+devtab entries to the underlying endpoint data structures.</P
+></BLOCKQUOTE
+></DIV
+></DIV
+><DIV
+CLASS="REFSECT2"
+><A
+NAME="AEN270"
+></A
+><H3
+>Presence</H3
+><P
+>The devtab entries are optional. If the USB device is accessed
 primarily by class-specific code such as the USB-ethernet package and
 that package uses the USB-specific API directly, the devtab entries
 are redundant. Even if application code does need to access the USB
@@ -414,64 +416,65 @@ serve no useful purpose, but they still 
 is possible to suppress the presence of these entries by disabling the
 configuration option
 <TT
-CLASS="LITERAL">
-CYGGLO_IO_USB_SLAVE_PROVIDE_DEVTAB_ENTRIES</TT>
-.</P>
-</DIV>
-</DIV>
-<DIV
-CLASS="NAVFOOTER">
-<HR
+CLASS="LITERAL"
+>CYGGLO_IO_USB_SLAVE_PROVIDE_DEVTAB_ENTRIES</TT
+>.</P
+></DIV
+></DIV
+><DIV
+CLASS="NAVFOOTER"
+><HR
 ALIGN="LEFT"
 WIDTH="100%"><TABLE
 WIDTH="100%"
 BORDER="0"
 CELLPADDING="0"
-CELLSPACING="0">
-<TR>
-<TD
+CELLSPACING="0"
+><TR
+><TD
 WIDTH="33%"
 ALIGN="left"
-VALIGN="top">
-<A
-HREF="usbs-start.html">
-Prev</A>
-</TD>
-<TD
+VALIGN="top"
+><A
+HREF="usbs-start.html"
+>Prev</A
+></TD
+><TD
 WIDTH="34%"
 ALIGN="center"
-VALIGN="top">
-<A
-HREF="io-usb-slave.html">
-Home</A>
-</TD>
-<TD
+VALIGN="top"
+><A
+HREF="io-usb-slave.html"
+>Home</A
+></TD
+><TD
 WIDTH="33%"
 ALIGN="right"
-VALIGN="top">
-<A
-HREF="usbs-start-rx.html">
-Next</A>
-</TD>
-</TR>
-<TR>
-<TD
+VALIGN="top"
+><A
+HREF="usbs-start-rx.html"
+>Next</A
+></TD
+></TR
+><TR
+><TD
 WIDTH="33%"
 ALIGN="left"
-VALIGN="top">
-Starting up a USB Device</TD>
-<TD
+VALIGN="top"
+>Starting up a USB Device</TD
+><TD
 WIDTH="34%"
 ALIGN="center"
-VALIGN="top">
-&nbsp;</TD>
-<TD
+VALIGN="top"
+>&nbsp;</TD
+><TD
 WIDTH="33%"
 ALIGN="right"
-VALIGN="top">
-Receiving Data from the Host</TD>
-</TR>
-</TABLE>
-</DIV>
-</BODY>
-</HTML>
+VALIGN="top"
+>Receiving Data from the Host</TD
+></TR
+></TABLE
+></DIV
+></BODY
+></HTML
+>
\ No newline at end of file