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unknown authored and Jeff Garzik committed May 13, 2005
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2 changes: 1 addition & 1 deletion [refs]
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---
refs/heads/master: 105adfc63f921a9976c5abc4ff079e9fec197ed7
refs/heads/master: fff9cfd99c0f88645c3f50d7476d6c8cef99f140
5 changes: 3 additions & 2 deletions trunk/CREDITS
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Expand Up @@ -882,12 +882,13 @@ S: Blacksburg, Virginia 24061
S: USA

N: Randy Dunlap
E: rdunlap@xenotime.net
E: rddunlap@osdl.org
W: http://www.xenotime.net/linux/linux.html
W: http://www.linux-usb.org
D: Linux-USB subsystem, USB core/UHCI/printer/storage drivers
D: x86 SMP, ACPI, bootflag hacking
S: (ask for current address)
S: 12725 SW Millikan Way, Suite 400
S: Beaverton, Oregon 97005
S: USA

N: Bob Dunlop
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156 changes: 32 additions & 124 deletions trunk/Documentation/DocBook/libata.tmpl
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Expand Up @@ -14,7 +14,7 @@
</authorgroup>

<copyright>
<year>2003-2005</year>
<year>2003</year>
<holder>Jeff Garzik</holder>
</copyright>

Expand Down Expand Up @@ -44,38 +44,30 @@

<toc></toc>

<chapter id="libataIntroduction">
<title>Introduction</title>
<chapter id="libataThanks">
<title>Thanks</title>
<para>
libATA is a library used inside the Linux kernel to support ATA host
controllers and devices. libATA provides an ATA driver API, class
transports for ATA and ATAPI devices, and SCSI&lt;-&gt;ATA translation
for ATA devices according to the T10 SAT specification.
The bulk of the ATA knowledge comes thanks to long conversations with
Andre Hedrick (www.linux-ide.org).
</para>
<para>
This Guide documents the libATA driver API, library functions, library
internals, and a couple sample ATA low-level drivers.
Thanks to Alan Cox for pointing out similarities
between SATA and SCSI, and in general for motivation to hack on
libata.
</para>
<para>
libata's device detection
method, ata_pio_devchk, and in general all the early probing was
based on extensive study of Hale Landis's probe/reset code in his
ATADRVR driver (www.ata-atapi.com).
</para>
</chapter>

<chapter id="libataDriverApi">
<title>libata Driver API</title>
<para>
struct ata_port_operations is defined for every low-level libata
hardware driver, and it controls how the low-level driver
interfaces with the ATA and SCSI layers.
</para>
<para>
FIS-based drivers will hook into the system with ->qc_prep() and
->qc_issue() high-level hooks. Hardware which behaves in a manner
similar to PCI IDE hardware may utilize several generic helpers,
defining at a bare minimum the bus I/O addresses of the ATA shadow
register blocks.
</para>
<sect1>
<title>struct ata_port_operations</title>

<sect2><title>Disable ATA port</title>
<programlisting>
void (*port_disable) (struct ata_port *);
</programlisting>
Expand All @@ -86,9 +78,6 @@ void (*port_disable) (struct ata_port *);
unplug).
</para>

</sect2>

<sect2><title>Post-IDENTIFY device configuration</title>
<programlisting>
void (*dev_config) (struct ata_port *, struct ata_device *);
</programlisting>
Expand All @@ -99,9 +88,6 @@ void (*dev_config) (struct ata_port *, struct ata_device *);
issue of SET FEATURES - XFER MODE, and prior to operation.
</para>

</sect2>

<sect2><title>Set PIO/DMA mode</title>
<programlisting>
void (*set_piomode) (struct ata_port *, struct ata_device *);
void (*set_dmamode) (struct ata_port *, struct ata_device *);
Expand All @@ -122,9 +108,6 @@ void (*post_set_mode) (struct ata_port *ap);
->set_dma_mode() is only called if DMA is possible.
</para>

</sect2>

<sect2><title>Taskfile read/write</title>
<programlisting>
void (*tf_load) (struct ata_port *ap, struct ata_taskfile *tf);
void (*tf_read) (struct ata_port *ap, struct ata_taskfile *tf);
Expand All @@ -137,9 +120,6 @@ void (*tf_read) (struct ata_port *ap, struct ata_taskfile *tf);
taskfile register values.
</para>

</sect2>

<sect2><title>ATA command execute</title>
<programlisting>
void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
</programlisting>
Expand All @@ -149,51 +129,27 @@ void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
->tf_load(), to be initiated in hardware.
</para>

</sect2>

<sect2><title>Per-cmd ATAPI DMA capabilities filter</title>
<programlisting>
int (*check_atapi_dma) (struct ata_queued_cmd *qc);
</programlisting>

<para>
Allow low-level driver to filter ATA PACKET commands, returning a status
indicating whether or not it is OK to use DMA for the supplied PACKET
command.
</para>

</sect2>

<sect2><title>Read specific ATA shadow registers</title>
<programlisting>
u8 (*check_status)(struct ata_port *ap);
u8 (*check_altstatus)(struct ata_port *ap);
u8 (*check_err)(struct ata_port *ap);
void (*dev_select)(struct ata_port *ap, unsigned int device);
</programlisting>

<para>
Reads the Status/AltStatus/Error ATA shadow register from
hardware. On some hardware, reading the Status register has
the side effect of clearing the interrupt condition.
Reads the Status ATA shadow register from hardware. On some
hardware, this has the side effect of clearing the interrupt
condition.
</para>

</sect2>

<sect2><title>Select ATA device on bus</title>
<programlisting>
void (*dev_select)(struct ata_port *ap, unsigned int device);
</programlisting>

<para>
Issues the low-level hardware command(s) that causes one of N
hardware devices to be considered 'selected' (active and
available for use) on the ATA bus. This generally has no
meaning on FIS-based devices.
available for use) on the ATA bus.
</para>

</sect2>

<sect2><title>Reset ATA bus</title>
<programlisting>
void (*phy_reset) (struct ata_port *ap);
</programlisting>
Expand All @@ -206,31 +162,17 @@ void (*phy_reset) (struct ata_port *ap);
functions ata_bus_reset() or sata_phy_reset() for this hook.
</para>

</sect2>

<sect2><title>Control PCI IDE BMDMA engine</title>
<programlisting>
void (*bmdma_setup) (struct ata_queued_cmd *qc);
void (*bmdma_start) (struct ata_queued_cmd *qc);
void (*bmdma_stop) (struct ata_port *ap);
u8 (*bmdma_status) (struct ata_port *ap);
</programlisting>

<para>
When setting up an IDE BMDMA transaction, these hooks arm
(->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop)
the hardware's DMA engine. ->bmdma_status is used to read the standard
PCI IDE DMA Status register.
When setting up an IDE BMDMA transaction, these hooks arm
(->bmdma_setup) and fire (->bmdma_start) the hardware's DMA
engine.
</para>

<para>
These hooks are typically either no-ops, or simply not implemented, in
FIS-based drivers.
</para>

</sect2>

<sect2><title>High-level taskfile hooks</title>
<programlisting>
void (*qc_prep) (struct ata_queued_cmd *qc);
int (*qc_issue) (struct ata_queued_cmd *qc);
Expand All @@ -248,26 +190,20 @@ int (*qc_issue) (struct ata_queued_cmd *qc);
->qc_issue is used to make a command active, once the hardware
and S/G tables have been prepared. IDE BMDMA drivers use the
helper function ata_qc_issue_prot() for taskfile protocol-based
dispatch. More advanced drivers implement their own ->qc_issue.
dispatch. More advanced drivers roll their own ->qc_issue
implementation, using this as the "issue new ATA command to
hardware" hook.
</para>

</sect2>

<sect2><title>Timeout (error) handling</title>
<programlisting>
void (*eng_timeout) (struct ata_port *ap);
</programlisting>

<para>
This is a high level error handling function, called from the
error handling thread, when a command times out. Most newer
hardware will implement its own error handling code here. IDE BMDMA
drivers may use the helper function ata_eng_timeout().
This is a high level error handling function, called from the
error handling thread, when a command times out.
</para>

</sect2>

<sect2><title>Hardware interrupt handling</title>
<programlisting>
irqreturn_t (*irq_handler)(int, void *, struct pt_regs *);
void (*irq_clear) (struct ata_port *);
Expand All @@ -280,9 +216,6 @@ void (*irq_clear) (struct ata_port *);
is quiet.
</para>

</sect2>

<sect2><title>SATA phy read/write</title>
<programlisting>
u32 (*scr_read) (struct ata_port *ap, unsigned int sc_reg);
void (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
Expand All @@ -294,9 +227,6 @@ void (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
if ->phy_reset hook called the sata_phy_reset() helper function.
</para>

</sect2>

<sect2><title>Init and shutdown</title>
<programlisting>
int (*port_start) (struct ata_port *ap);
void (*port_stop) (struct ata_port *ap);
Expand All @@ -310,17 +240,15 @@ void (*host_stop) (struct ata_host_set *host_set);
tasks.
</para>
<para>
->host_stop() is called when the rmmod or hot unplug process
begins. The hook must stop all hardware interrupts, DMA
engines, etc.
</para>
<para>
->port_stop() is called after ->host_stop(). It's sole function
is to release DMA/memory resources, now that they are no longer
actively being used.
</para>
<para>
->host_stop() is called after all ->port_stop() calls
have completed. The hook must finalize hardware shutdown, release DMA
and other resources, etc.
</para>

</sect2>

</sect1>
</chapter>
Expand Down Expand Up @@ -351,24 +279,4 @@ and other resources, etc.
!Idrivers/scsi/sata_sil.c
</chapter>

<chapter id="libataThanks">
<title>Thanks</title>
<para>
The bulk of the ATA knowledge comes thanks to long conversations with
Andre Hedrick (www.linux-ide.org), and long hours pondering the ATA
and SCSI specifications.
</para>
<para>
Thanks to Alan Cox for pointing out similarities
between SATA and SCSI, and in general for motivation to hack on
libata.
</para>
<para>
libata's device detection
method, ata_pio_devchk, and in general all the early probing was
based on extensive study of Hale Landis's probe/reset code in his
ATADRVR driver (www.ata-atapi.com).
</para>
</chapter>

</book>
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