[deliverable/linux.git] / Documentation / DocBook / libata.tmpl

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
	"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>

<book id="libataDevGuide">
 <bookinfo>
  <title>libATA Developer's Guide</title>
  
  <authorgroup>
   <author>
    <firstname>Jeff</firstname>
    <surname>Garzik</surname>
   </author>
  </authorgroup>

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

  <legalnotice>
   <para>
   The contents of this file are subject to the Open
   Software License version 1.1 that can be found at
   <ulink url="http://www.opensource.org/licenses/osl-1.1.txt">http://www.opensource.org/licenses/osl-1.1.txt</ulink> and is included herein
   by reference.
   </para>

   <para>
   Alternatively, the contents of this file may be used under the terms
   of the GNU General Public License version 2 (the "GPL") as distributed
   in the kernel source COPYING file, in which case the provisions of
   the GPL are applicable instead of the above.  If you wish to allow
   the use of your version of this file only under the terms of the
   GPL and not to allow others to use your version of this file under
   the OSL, indicate your decision by deleting the provisions above and
   replace them with the notice and other provisions required by the GPL.
   If you do not delete the provisions above, a recipient may use your
   version of this file under either the OSL or the GPL.
   </para>

  </legalnotice>
 </bookinfo>

<toc></toc>

  <chapter id="libataIntroduction">
     <title>Introduction</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.
  </para>
  <para>
  This Guide documents the libATA driver API, library functions, library
  internals, and a couple sample ATA low-level drivers.
  </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>

	<para>
	Called from ata_bus_probe() and ata_bus_reset() error paths,
	as well as when unregistering from the SCSI module (rmmod, hot
	unplug).
	This function should do whatever needs to be done to take the
	port out of use.  In most cases, ata_port_disable() can be used
	as this hook.
	</para>
	<para>
	Called from ata_bus_probe() on a failed probe.
	Called from ata_bus_reset() on a failed bus reset.
	Called from ata_scsi_release().
	</para>

	</sect2>

	<sect2><title>Post-IDENTIFY device configuration</title>
	<programlisting>
void (*dev_config) (struct ata_port *, struct ata_device *);
	</programlisting>

	<para>
	Called after IDENTIFY [PACKET] DEVICE is issued to each device
	found.  Typically used to apply device-specific fixups prior to
	issue of SET FEATURES - XFER MODE, and prior to operation.
	</para>
	<para>
	Called by ata_device_add() after ata_dev_identify() determines
	a device is present.
	</para>
	<para>
	This entry may be specified as NULL in ata_port_operations.
	</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 *);
void (*post_set_mode) (struct ata_port *ap);
	</programlisting>

	<para>
	Hooks called prior to the issue of SET FEATURES - XFER MODE
	command.  dev->pio_mode is guaranteed to be valid when
	->set_piomode() is called, and dev->dma_mode is guaranteed to be
	valid when ->set_dmamode() is called.  ->post_set_mode() is
	called unconditionally, after the SET FEATURES - XFER MODE
	command completes successfully.
	</para>

	<para>
	->set_piomode() is always called (if present), but
	->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);
	</programlisting>

	<para>
	->tf_load() is called to load the given taskfile into hardware
	registers / DMA buffers.  ->tf_read() is called to read the
	hardware registers / DMA buffers, to obtain the current set of
	taskfile register values.
	Most drivers for taskfile-based hardware (PIO or MMIO) use
	ata_tf_load() and ata_tf_read() for these hooks.
	</para>

	</sect2>

	<sect2><title>ATA command execute</title>
	<programlisting>
void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
	</programlisting>

	<para>
	causes an ATA command, previously loaded with
	->tf_load(), to be initiated in hardware.
	Most drivers for taskfile-based hardware use ata_exec_command()
	for this hook.
	</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>
	<para>
	This hook may be specified as NULL, in which case libata will
	assume that atapi dma can be supported.
	</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);
	</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.
	Most drivers for taskfile-based hardware use
	ata_check_status() for this hook.
	</para>
	<para>
	Note that because this is called from ata_device_add(), at
	least a dummy function that clears device interrupts must be
	provided for all drivers, even if the controller doesn't
	actually have a taskfile status register.
	</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.
	</para>
	<para>
	Most drivers for taskfile-based hardware use
	ata_std_dev_select() for this hook.  Controllers which do not
	support second drives on a port (such as SATA contollers) will
	use ata_noop_dev_select().
	</para>

	</sect2>

	<sect2><title>Reset ATA bus</title>
	<programlisting>
void (*phy_reset) (struct ata_port *ap);
	</programlisting>

	<para>
	The very first step in the probe phase.  Actions vary depending
	on the bus type, typically.  After waking up the device and probing
	for device presence (PATA and SATA), typically a soft reset
	(SRST) will be performed.  Drivers typically use the helper
	functions ata_bus_reset() or sata_phy_reset() for this hook.
	Many SATA drivers use sata_phy_reset() or call it from within
	their own phy_reset() functions.
	</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.
	</para>

	<para>
These hooks are typically either no-ops, or simply not implemented, in
FIS-based drivers.
	</para>
	<para>
Most legacy IDE drivers use ata_bmdma_setup() for the bmdma_setup()
hook.  ata_bmdma_setup() will write the pointer to the PRD table to
the IDE PRD Table Address register, enable DMA in the DMA Command
register, and call exec_command() to begin the transfer.
	</para>
	<para>
Most legacy IDE drivers use ata_bmdma_start() for the bmdma_start()
hook.  ata_bmdma_start() will write the ATA_DMA_START flag to the DMA
Command register.
	</para>
	<para>
Many legacy IDE drivers use ata_bmdma_stop() for the bmdma_stop()
hook.  ata_bmdma_stop() clears the ATA_DMA_START flag in the DMA
command register.
	</para>
	<para>
Many legacy IDE drivers use ata_bmdma_status() as the bmdma_status() hook.
	</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);
	</programlisting>

	<para>
	Higher-level hooks, these two hooks can potentially supercede
	several of the above taskfile/DMA engine hooks.  ->qc_prep is
	called after the buffers have been DMA-mapped, and is typically
	used to populate the hardware's DMA scatter-gather table.
	Most drivers use the standard ata_qc_prep() helper function, but
	more advanced drivers roll their own.
	</para>
	<para>
	->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.
	</para>
	<para>
	ata_qc_issue_prot() calls ->tf_load(), ->bmdma_setup(), and
	->bmdma_start() as necessary to initiate a transfer.
	</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().
	</para>

	</sect2>

	<sect2><title>Hardware interrupt handling</title>
	<programlisting>
irqreturn_t (*irq_handler)(int, void *, struct pt_regs *);
void (*irq_clear) (struct ata_port *);
	</programlisting>

	<para>
	->irq_handler is the interrupt handling routine registered with
	the system, by libata.  ->irq_clear is called during probe just
	before the interrupt handler is registered, to be sure hardware
	is quiet.
	</para>
	<para>
	The second argument, dev_instance, should be cast to a pointer
	to struct ata_host_set.
	</para>
	<para>
	Most legacy IDE drivers use ata_interrupt() for the
	irq_handler hook, which scans all ports in the host_set,
	determines which queued command was active (if any), and calls
	ata_host_intr(ap,qc).
	</para>
	<para>
	Most legacy IDE drivers use ata_bmdma_irq_clear() for the
	irq_clear() hook, which simply clears the interrupt and error
	flags in the DMA status register.
	</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,
                   u32 val);
	</programlisting>

	<para>
	Read and write standard SATA phy registers.  Currently only used
	if ->phy_reset hook called the sata_phy_reset() helper function.
	sc_reg is one of SCR_STATUS, SCR_CONTROL, SCR_ERROR, or SCR_ACTIVE.
	</para>

	</sect2>

	<sect2><title>Init and shutdown</title>
	<programlisting>
int (*port_start) (struct ata_port *ap);
void (*port_stop) (struct ata_port *ap);
void (*host_stop) (struct ata_host_set *host_set);
	</programlisting>

	<para>
	->port_start() is called just after the data structures for each
	port are initialized.  Typically this is used to alloc per-port
	DMA buffers / tables / rings, enable DMA engines, and similar
	tasks.  Some drivers also use this entry point as a chance to
	allocate driver-private memory for ap->private_data.
	</para>
	<para>
	Many drivers use ata_port_start() as this hook or call
	it from their own port_start() hooks.  ata_port_start()
	allocates space for a legacy IDE PRD table and returns.
	</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.  Many drivers also free driver-private
	data from port at this time.
	</para>
	<para>
	Many drivers use ata_port_stop() as this hook, which frees the
	PRD table.
	</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.
	This hook may be specified as NULL, in which case it is not called.
	</para>

	</sect2>

     </sect1>
  </chapter>

  <chapter id="libataExt">
     <title>libata Library</title>
!Edrivers/scsi/libata-core.c
  </chapter>

  <chapter id="libataInt">
     <title>libata Core Internals</title>
!Idrivers/scsi/libata-core.c
  </chapter>

  <chapter id="libataScsiInt">
     <title>libata SCSI translation/emulation</title>
!Edrivers/scsi/libata-scsi.c
!Idrivers/scsi/libata-scsi.c
  </chapter>

  <chapter id="PiixInt">
     <title>ata_piix Internals</title>
!Idrivers/scsi/ata_piix.c
  </chapter>

  <chapter id="SILInt">
     <title>sata_sil Internals</title>
!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>
Commit	Line	Data
1da177e4 LT	1	<?xml version="1.0" encoding="UTF-8"?>
	2	<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
	3	"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
	4
	5	<book id="libataDevGuide">
	6	<bookinfo>
	7	<title>libATA Developer's Guide</title>
	8
	9	<authorgroup>
	10	<author>
	11	<firstname>Jeff</firstname>
	12	<surname>Garzik</surname>
	13	</author>
	14	</authorgroup>
	15
	16	<copyright>
780a87f7	17	<year>2003-2005</year>
1da177e4 LT	18	<holder>Jeff Garzik</holder>
	19	</copyright>
	20
	21	<legalnotice>
	22	<para>
	23	The contents of this file are subject to the Open
	24	Software License version 1.1 that can be found at
	25	<ulink url="http://www.opensource.org/licenses/osl-1.1.txt">http://www.opensource.org/licenses/osl-1.1.txt</ulink> and is included herein
	26	by reference.
	27	</para>
	28
	29	<para>
	30	Alternatively, the contents of this file may be used under the terms
	31	of the GNU General Public License version 2 (the "GPL") as distributed
	32	in the kernel source COPYING file, in which case the provisions of
	33	the GPL are applicable instead of the above. If you wish to allow
	34	the use of your version of this file only under the terms of the
	35	GPL and not to allow others to use your version of this file under
	36	the OSL, indicate your decision by deleting the provisions above and
	37	replace them with the notice and other provisions required by the GPL.
	38	If you do not delete the provisions above, a recipient may use your
	39	version of this file under either the OSL or the GPL.
	40	</para>
	41
	42	</legalnotice>
	43	</bookinfo>
	44
	45	<toc></toc>
	46
07dd39b9 JG	47	<chapter id="libataIntroduction">
	48	<title>Introduction</title>
	49	<para>
	50	libATA is a library used inside the Linux kernel to support ATA host
	51	controllers and devices. libATA provides an ATA driver API, class
	52	transports for ATA and ATAPI devices, and SCSI<->ATA translation
	53	for ATA devices according to the T10 SAT specification.
	54	</para>
	55	<para>
	56	This Guide documents the libATA driver API, library functions, library
	57	internals, and a couple sample ATA low-level drivers.
	58	</para>
	59	</chapter>
	60
1da177e4 LT	61	<chapter id="libataDriverApi">
1da177e4 LT	62	<title>libata Driver API</title>
92bab26b JG	63	<para>
	64	struct ata_port_operations is defined for every low-level libata
	65	hardware driver, and it controls how the low-level driver
	66	interfaces with the ATA and SCSI layers.
	67	</para>
	68	<para>
	69	FIS-based drivers will hook into the system with ->qc_prep() and
	70	->qc_issue() high-level hooks. Hardware which behaves in a manner
	71	similar to PCI IDE hardware may utilize several generic helpers,
	72	defining at a bare minimum the bus I/O addresses of the ATA shadow
	73	register blocks.
	74	</para>
1da177e4 LT	75	<sect1>
	76	<title>struct ata_port_operations</title>
	77
92bab26b	78	<sect2><title>Disable ATA port</title>
1da177e4 LT	79	<programlisting>
	80	void (port_disable) (struct ata_port );
	81	</programlisting>
	82
	83	<para>
	84	Called from ata_bus_probe() and ata_bus_reset() error paths,
	85	as well as when unregistering from the SCSI module (rmmod, hot
	86	unplug).
8b2af8f0 EF	87	This function should do whatever needs to be done to take the
	88	port out of use. In most cases, ata_port_disable() can be used
	89	as this hook.
	90	</para>
	91	<para>
	92	Called from ata_bus_probe() on a failed probe.
	93	Called from ata_bus_reset() on a failed bus reset.
	94	Called from ata_scsi_release().
1da177e4 LT	95	</para>
1da177e4 LT	96
92bab26b JG	97	</sect2>
	98
	99	<sect2><title>Post-IDENTIFY device configuration</title>
1da177e4 LT	100	<programlisting>
	101	void (dev_config) (struct ata_port , struct ata_device *);
	102	</programlisting>
	103
	104	<para>
	105	Called after IDENTIFY [PACKET] DEVICE is issued to each device
	106	found. Typically used to apply device-specific fixups prior to
	107	issue of SET FEATURES - XFER MODE, and prior to operation.
	108	</para>
8b2af8f0 EF	109	<para>
	110	Called by ata_device_add() after ata_dev_identify() determines
	111	a device is present.
	112	</para>
	113	<para>
	114	This entry may be specified as NULL in ata_port_operations.
	115	</para>
1da177e4	116
92bab26b JG	117	</sect2>
	118
	119	<sect2><title>Set PIO/DMA mode</title>
1da177e4 LT	120	<programlisting>
	121	void (set_piomode) (struct ata_port , struct ata_device *);
	122	void (set_dmamode) (struct ata_port , struct ata_device *);
	123	void (post_set_mode) (struct ata_port ap);
	124	</programlisting>
	125
	126	<para>
	127	Hooks called prior to the issue of SET FEATURES - XFER MODE
	128	command. dev->pio_mode is guaranteed to be valid when
	129	->set_piomode() is called, and dev->dma_mode is guaranteed to be
	130	valid when ->set_dmamode() is called. ->post_set_mode() is
	131	called unconditionally, after the SET FEATURES - XFER MODE
	132	command completes successfully.
	133	</para>
	134
	135	<para>
	136	->set_piomode() is always called (if present), but
	137	->set_dma_mode() is only called if DMA is possible.
	138	</para>
	139
92bab26b JG	140	</sect2>
	141
	142	<sect2><title>Taskfile read/write</title>
1da177e4 LT	143	<programlisting>
	144	void (tf_load) (struct ata_port ap, struct ata_taskfile *tf);
	145	void (tf_read) (struct ata_port ap, struct ata_taskfile *tf);
	146	</programlisting>
	147
	148	<para>
	149	->tf_load() is called to load the given taskfile into hardware
	150	registers / DMA buffers. ->tf_read() is called to read the
	151	hardware registers / DMA buffers, to obtain the current set of
	152	taskfile register values.
8b2af8f0 EF	153	Most drivers for taskfile-based hardware (PIO or MMIO) use
8b2af8f0 EF	154	ata_tf_load() and ata_tf_read() for these hooks.
1da177e4 LT	155	</para>
1da177e4 LT	156
92bab26b JG	157	</sect2>
	158
	159	<sect2><title>ATA command execute</title>
1da177e4 LT	160	<programlisting>
	161	void (exec_command)(struct ata_port ap, struct ata_taskfile *tf);
	162	</programlisting>
	163
	164	<para>
	165	causes an ATA command, previously loaded with
	166	->tf_load(), to be initiated in hardware.
8b2af8f0 EF	167	Most drivers for taskfile-based hardware use ata_exec_command()
8b2af8f0 EF	168	for this hook.
1da177e4 LT	169	</para>
1da177e4 LT	170
92bab26b JG	171	</sect2>
	172
	173	<sect2><title>Per-cmd ATAPI DMA capabilities filter</title>
780a87f7 JG	174	<programlisting>
	175	int (check_atapi_dma) (struct ata_queued_cmd qc);
	176	</programlisting>
	177
	178	<para>
	179	Allow low-level driver to filter ATA PACKET commands, returning a status
	180	indicating whether or not it is OK to use DMA for the supplied PACKET
	181	command.
	182	</para>
8b2af8f0 EF	183	<para>
	184	This hook may be specified as NULL, in which case libata will
	185	assume that atapi dma can be supported.
	186	</para>
780a87f7	187
92bab26b JG	188	</sect2>
	189
	190	<sect2><title>Read specific ATA shadow registers</title>
1da177e4 LT	191	<programlisting>
1da177e4 LT	192	u8 (check_status)(struct ata_port ap);
780a87f7 JG	193	u8 (check_altstatus)(struct ata_port ap);
780a87f7 JG	194	u8 (check_err)(struct ata_port ap);
1da177e4 LT	195	</programlisting>
	196
	197	<para>
780a87f7 JG	198	Reads the Status/AltStatus/Error ATA shadow register from
	199	hardware. On some hardware, reading the Status register has
	200	the side effect of clearing the interrupt condition.
8b2af8f0 EF	201	Most drivers for taskfile-based hardware use
	202	ata_check_status() for this hook.
	203	</para>
	204	<para>
	205	Note that because this is called from ata_device_add(), at
	206	least a dummy function that clears device interrupts must be
	207	provided for all drivers, even if the controller doesn't
	208	actually have a taskfile status register.
1da177e4 LT	209	</para>
1da177e4 LT	210
92bab26b JG	211	</sect2>
	212
	213	<sect2><title>Select ATA device on bus</title>
1da177e4 LT	214	<programlisting>
	215	void (dev_select)(struct ata_port ap, unsigned int device);
	216	</programlisting>
	217
	218	<para>
	219	Issues the low-level hardware command(s) that causes one of N
	220	hardware devices to be considered 'selected' (active and
780a87f7	221	available for use) on the ATA bus. This generally has no
8b2af8f0 EF	222	meaning on FIS-based devices.
	223	</para>
	224	<para>
	225	Most drivers for taskfile-based hardware use
	226	ata_std_dev_select() for this hook. Controllers which do not
	227	support second drives on a port (such as SATA contollers) will
	228	use ata_noop_dev_select().
1da177e4 LT	229	</para>
1da177e4 LT	230
92bab26b JG	231	</sect2>
	232
	233	<sect2><title>Reset ATA bus</title>
1da177e4 LT	234	<programlisting>
	235	void (phy_reset) (struct ata_port ap);
	236	</programlisting>
	237
	238	<para>
	239	The very first step in the probe phase. Actions vary depending
	240	on the bus type, typically. After waking up the device and probing
	241	for device presence (PATA and SATA), typically a soft reset
	242	(SRST) will be performed. Drivers typically use the helper
	243	functions ata_bus_reset() or sata_phy_reset() for this hook.
8b2af8f0 EF	244	Many SATA drivers use sata_phy_reset() or call it from within
8b2af8f0 EF	245	their own phy_reset() functions.
1da177e4 LT	246	</para>
1da177e4 LT	247
92bab26b JG	248	</sect2>
	249
	250	<sect2><title>Control PCI IDE BMDMA engine</title>
1da177e4 LT	251	<programlisting>
	252	void (bmdma_setup) (struct ata_queued_cmd qc);
	253	void (bmdma_start) (struct ata_queued_cmd qc);
780a87f7 JG	254	void (bmdma_stop) (struct ata_port ap);
780a87f7 JG	255	u8 (bmdma_status) (struct ata_port ap);
1da177e4 LT	256	</programlisting>
	257
	258	<para>
780a87f7 JG	259	When setting up an IDE BMDMA transaction, these hooks arm
	260	(->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop)
	261	the hardware's DMA engine. ->bmdma_status is used to read the standard
	262	PCI IDE DMA Status register.
	263	</para>
	264
	265	<para>
	266	These hooks are typically either no-ops, or simply not implemented, in
	267	FIS-based drivers.
1da177e4	268	</para>
8b2af8f0 EF	269	<para>
	270	Most legacy IDE drivers use ata_bmdma_setup() for the bmdma_setup()
	271	hook. ata_bmdma_setup() will write the pointer to the PRD table to
	272	the IDE PRD Table Address register, enable DMA in the DMA Command
	273	register, and call exec_command() to begin the transfer.
	274	</para>
	275	<para>
	276	Most legacy IDE drivers use ata_bmdma_start() for the bmdma_start()
	277	hook. ata_bmdma_start() will write the ATA_DMA_START flag to the DMA
	278	Command register.
	279	</para>
	280	<para>
	281	Many legacy IDE drivers use ata_bmdma_stop() for the bmdma_stop()
	282	hook. ata_bmdma_stop() clears the ATA_DMA_START flag in the DMA
	283	command register.
	284	</para>
	285	<para>
	286	Many legacy IDE drivers use ata_bmdma_status() as the bmdma_status() hook.
	287	</para>
1da177e4	288
92bab26b JG	289	</sect2>
	290
	291	<sect2><title>High-level taskfile hooks</title>
1da177e4 LT	292	<programlisting>
	293	void (qc_prep) (struct ata_queued_cmd qc);
	294	int (qc_issue) (struct ata_queued_cmd qc);
	295	</programlisting>
	296
	297	<para>
	298	Higher-level hooks, these two hooks can potentially supercede
	299	several of the above taskfile/DMA engine hooks. ->qc_prep is
	300	called after the buffers have been DMA-mapped, and is typically
	301	used to populate the hardware's DMA scatter-gather table.
	302	Most drivers use the standard ata_qc_prep() helper function, but
	303	more advanced drivers roll their own.
	304	</para>
	305	<para>
	306	->qc_issue is used to make a command active, once the hardware
	307	and S/G tables have been prepared. IDE BMDMA drivers use the
	308	helper function ata_qc_issue_prot() for taskfile protocol-based
780a87f7	309	dispatch. More advanced drivers implement their own ->qc_issue.
1da177e4	310	</para>
8b2af8f0 EF	311	<para>
	312	ata_qc_issue_prot() calls ->tf_load(), ->bmdma_setup(), and
	313	->bmdma_start() as necessary to initiate a transfer.
	314	</para>
1da177e4	315
92bab26b JG	316	</sect2>
	317
	318	<sect2><title>Timeout (error) handling</title>
1da177e4 LT	319	<programlisting>
	320	void (eng_timeout) (struct ata_port ap);
	321	</programlisting>
	322
	323	<para>
780a87f7 JG	324	This is a high level error handling function, called from the
	325	error handling thread, when a command times out. Most newer
	326	hardware will implement its own error handling code here. IDE BMDMA
	327	drivers may use the helper function ata_eng_timeout().
1da177e4 LT	328	</para>
1da177e4 LT	329
92bab26b JG	330	</sect2>
	331
	332	<sect2><title>Hardware interrupt handling</title>
1da177e4 LT	333	<programlisting>
	334	irqreturn_t (irq_handler)(int, void , struct pt_regs *);
	335	void (irq_clear) (struct ata_port );
	336	</programlisting>
	337
	338	<para>
	339	->irq_handler is the interrupt handling routine registered with
	340	the system, by libata. ->irq_clear is called during probe just
	341	before the interrupt handler is registered, to be sure hardware
	342	is quiet.
	343	</para>
8b2af8f0 EF	344	<para>
	345	The second argument, dev_instance, should be cast to a pointer
	346	to struct ata_host_set.
	347	</para>
	348	<para>
	349	Most legacy IDE drivers use ata_interrupt() for the
	350	irq_handler hook, which scans all ports in the host_set,
	351	determines which queued command was active (if any), and calls
	352	ata_host_intr(ap,qc).
	353	</para>
	354	<para>
	355	Most legacy IDE drivers use ata_bmdma_irq_clear() for the
	356	irq_clear() hook, which simply clears the interrupt and error
	357	flags in the DMA status register.
	358	</para>
1da177e4	359
92bab26b JG	360	</sect2>
	361
	362	<sect2><title>SATA phy read/write</title>
1da177e4 LT	363	<programlisting>
	364	u32 (scr_read) (struct ata_port ap, unsigned int sc_reg);
	365	void (scr_write) (struct ata_port ap, unsigned int sc_reg,
	366	u32 val);
	367	</programlisting>
	368
	369	<para>
	370	Read and write standard SATA phy registers. Currently only used
	371	if ->phy_reset hook called the sata_phy_reset() helper function.
8b2af8f0	372	sc_reg is one of SCR_STATUS, SCR_CONTROL, SCR_ERROR, or SCR_ACTIVE.
1da177e4 LT	373	</para>
1da177e4 LT	374
92bab26b JG	375	</sect2>
	376
	377	<sect2><title>Init and shutdown</title>
1da177e4 LT	378	<programlisting>
	379	int (port_start) (struct ata_port ap);
	380	void (port_stop) (struct ata_port ap);
	381	void (host_stop) (struct ata_host_set host_set);
	382	</programlisting>
	383
	384	<para>
	385	->port_start() is called just after the data structures for each
	386	port are initialized. Typically this is used to alloc per-port
	387	DMA buffers / tables / rings, enable DMA engines, and similar
8b2af8f0 EF	388	tasks. Some drivers also use this entry point as a chance to
	389	allocate driver-private memory for ap->private_data.
	390	</para>
	391	<para>
	392	Many drivers use ata_port_start() as this hook or call
	393	it from their own port_start() hooks. ata_port_start()
	394	allocates space for a legacy IDE PRD table and returns.
1da177e4 LT	395	</para>
1da177e4 LT	396	<para>
1da177e4 LT	397	->port_stop() is called after ->host_stop(). It's sole function
1da177e4 LT	398	is to release DMA/memory resources, now that they are no longer
8b2af8f0 EF	399	actively being used. Many drivers also free driver-private
	400	data from port at this time.
	401	</para>
	402	<para>
	403	Many drivers use ata_port_stop() as this hook, which frees the
	404	PRD table.
1da177e4	405	</para>
780a87f7 JG	406	<para>
	407	->host_stop() is called after all ->port_stop() calls
	408	have completed. The hook must finalize hardware shutdown, release DMA
	409	and other resources, etc.
8b2af8f0	410	This hook may be specified as NULL, in which case it is not called.
780a87f7	411	</para>
1da177e4	412
92bab26b JG	413	</sect2>
92bab26b JG	414
1da177e4 LT	415	</sect1>
	416	</chapter>
	417
	418	<chapter id="libataExt">
	419	<title>libata Library</title>
	420	!Edrivers/scsi/libata-core.c
	421	</chapter>
	422
	423	<chapter id="libataInt">
	424	<title>libata Core Internals</title>
	425	!Idrivers/scsi/libata-core.c
	426	</chapter>
	427
	428	<chapter id="libataScsiInt">
	429	<title>libata SCSI translation/emulation</title>
	430	!Edrivers/scsi/libata-scsi.c
	431	!Idrivers/scsi/libata-scsi.c
	432	</chapter>
	433
	434	<chapter id="PiixInt">
	435	<title>ata_piix Internals</title>
	436	!Idrivers/scsi/ata_piix.c
	437	</chapter>
	438
	439	<chapter id="SILInt">
	440	<title>sata_sil Internals</title>
	441	!Idrivers/scsi/sata_sil.c
	442	</chapter>
	443
0cba632b JG	444	<chapter id="libataThanks">
	445	<title>Thanks</title>
	446	<para>
	447	The bulk of the ATA knowledge comes thanks to long conversations with
	448	Andre Hedrick (www.linux-ide.org), and long hours pondering the ATA
	449	and SCSI specifications.
	450	</para>
	451	<para>
	452	Thanks to Alan Cox for pointing out similarities
	453	between SATA and SCSI, and in general for motivation to hack on
	454	libata.
	455	</para>
	456	<para>
	457	libata's device detection
	458	method, ata_pio_devchk, and in general all the early probing was
	459	based on extensive study of Hale Landis's probe/reset code in his
	460	ATADRVR driver (www.ata-atapi.com).
	461	</para>
	462	</chapter>
	463
1da177e4	464	</book>