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Linus Torvalds committed Jun 2, 2005
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156 changes: 124 additions & 32 deletions Documentation/DocBook/libata.tmpl
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@
</authorgroup>

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

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

<toc></toc>

<chapter id="libataThanks">
<title>Thanks</title>
<chapter id="libataIntroduction">
<title>Introduction</title>
<para>
The bulk of the ATA knowledge comes thanks to long conversations with
Andre Hedrick (www.linux-ide.org).
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>
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).
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>
Expand All @@ -78,6 +86,9 @@ 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 @@ -88,6 +99,9 @@ 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 @@ -108,6 +122,9 @@ 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 @@ -120,6 +137,9 @@ 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 @@ -129,27 +149,51 @@ 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);
void (*dev_select)(struct ata_port *ap, unsigned int device);
u8 (*check_altstatus)(struct ata_port *ap);
u8 (*check_err)(struct ata_port *ap);
</programlisting>

<para>
Reads the Status ATA shadow register from hardware. On some
hardware, this has the side effect of clearing the interrupt
condition.
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.
</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.
available for use) on the ATA bus. This generally has no
meaning on FIS-based devices.
</para>

</sect2>

<sect2><title>Reset ATA bus</title>
<programlisting>
void (*phy_reset) (struct ata_port *ap);
</programlisting>
Expand All @@ -162,17 +206,31 @@ 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) and fire (->bmdma_start) the hardware's DMA
engine.
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>

</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 @@ -190,20 +248,26 @@ 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 roll their own ->qc_issue
implementation, using this as the "issue new ATA command to
hardware" hook.
dispatch. More advanced drivers implement their own ->qc_issue.
</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.
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 *);
Expand All @@ -216,6 +280,9 @@ 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 @@ -227,6 +294,9 @@ 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 @@ -240,15 +310,17 @@ 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 @@ -279,4 +351,24 @@ void (*host_stop) (struct ata_host_set *host_set);
!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>
16 changes: 0 additions & 16 deletions drivers/scsi/ata_piix.c
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Original file line number Diff line number Diff line change
Expand Up @@ -665,15 +665,6 @@ static int piix_init_one (struct pci_dev *pdev, const struct pci_device_id *ent)
return ata_pci_init_one(pdev, port_info, n_ports);
}

/**
* piix_init -
*
* LOCKING:
*
* RETURNS:
*
*/

static int __init piix_init(void)
{
int rc;
Expand All @@ -689,13 +680,6 @@ static int __init piix_init(void)
return 0;
}

/**
* piix_exit -
*
* LOCKING:
*
*/

static void __exit piix_exit(void)
{
pci_unregister_driver(&piix_pci_driver);
Expand Down
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