1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
282 lines
8.2 KiB
XML
282 lines
8.2 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
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<book id="libataDevGuide">
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<bookinfo>
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<title>libATA Developer's Guide</title>
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<authorgroup>
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<author>
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<firstname>Jeff</firstname>
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<surname>Garzik</surname>
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</author>
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</authorgroup>
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<copyright>
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<year>2003</year>
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<holder>Jeff Garzik</holder>
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</copyright>
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<legalnotice>
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<para>
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The contents of this file are subject to the Open
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Software License version 1.1 that can be found at
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<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
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by reference.
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</para>
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<para>
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Alternatively, the contents of this file may be used under the terms
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of the GNU General Public License version 2 (the "GPL") as distributed
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in the kernel source COPYING file, in which case the provisions of
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the GPL are applicable instead of the above. If you wish to allow
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the use of your version of this file only under the terms of the
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GPL and not to allow others to use your version of this file under
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the OSL, indicate your decision by deleting the provisions above and
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replace them with the notice and other provisions required by the GPL.
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If you do not delete the provisions above, a recipient may use your
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version of this file under either the OSL or the GPL.
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</para>
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</legalnotice>
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</bookinfo>
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<toc></toc>
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<chapter id="libataThanks">
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<title>Thanks</title>
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<para>
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The bulk of the ATA knowledge comes thanks to long conversations with
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Andre Hedrick (www.linux-ide.org).
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</para>
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<para>
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Thanks to Alan Cox for pointing out similarities
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between SATA and SCSI, and in general for motivation to hack on
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libata.
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</para>
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<para>
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libata's device detection
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method, ata_pio_devchk, and in general all the early probing was
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based on extensive study of Hale Landis's probe/reset code in his
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ATADRVR driver (www.ata-atapi.com).
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</para>
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</chapter>
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<chapter id="libataDriverApi">
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<title>libata Driver API</title>
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<sect1>
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<title>struct ata_port_operations</title>
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<programlisting>
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void (*port_disable) (struct ata_port *);
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</programlisting>
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<para>
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Called from ata_bus_probe() and ata_bus_reset() error paths,
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as well as when unregistering from the SCSI module (rmmod, hot
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unplug).
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</para>
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<programlisting>
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void (*dev_config) (struct ata_port *, struct ata_device *);
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</programlisting>
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<para>
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Called after IDENTIFY [PACKET] DEVICE is issued to each device
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found. Typically used to apply device-specific fixups prior to
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issue of SET FEATURES - XFER MODE, and prior to operation.
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</para>
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<programlisting>
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void (*set_piomode) (struct ata_port *, struct ata_device *);
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void (*set_dmamode) (struct ata_port *, struct ata_device *);
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void (*post_set_mode) (struct ata_port *ap);
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</programlisting>
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<para>
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Hooks called prior to the issue of SET FEATURES - XFER MODE
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command. dev->pio_mode is guaranteed to be valid when
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->set_piomode() is called, and dev->dma_mode is guaranteed to be
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valid when ->set_dmamode() is called. ->post_set_mode() is
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called unconditionally, after the SET FEATURES - XFER MODE
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command completes successfully.
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</para>
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<para>
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->set_piomode() is always called (if present), but
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->set_dma_mode() is only called if DMA is possible.
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</para>
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<programlisting>
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void (*tf_load) (struct ata_port *ap, struct ata_taskfile *tf);
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void (*tf_read) (struct ata_port *ap, struct ata_taskfile *tf);
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</programlisting>
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<para>
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->tf_load() is called to load the given taskfile into hardware
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registers / DMA buffers. ->tf_read() is called to read the
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hardware registers / DMA buffers, to obtain the current set of
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taskfile register values.
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</para>
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<programlisting>
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void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
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</programlisting>
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<para>
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causes an ATA command, previously loaded with
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->tf_load(), to be initiated in hardware.
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</para>
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<programlisting>
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u8 (*check_status)(struct ata_port *ap);
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void (*dev_select)(struct ata_port *ap, unsigned int device);
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</programlisting>
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<para>
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Reads the Status ATA shadow register from hardware. On some
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hardware, this has the side effect of clearing the interrupt
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condition.
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</para>
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<programlisting>
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void (*dev_select)(struct ata_port *ap, unsigned int device);
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</programlisting>
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<para>
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Issues the low-level hardware command(s) that causes one of N
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hardware devices to be considered 'selected' (active and
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available for use) on the ATA bus.
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</para>
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<programlisting>
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void (*phy_reset) (struct ata_port *ap);
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</programlisting>
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<para>
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The very first step in the probe phase. Actions vary depending
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on the bus type, typically. After waking up the device and probing
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for device presence (PATA and SATA), typically a soft reset
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(SRST) will be performed. Drivers typically use the helper
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functions ata_bus_reset() or sata_phy_reset() for this hook.
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</para>
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<programlisting>
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void (*bmdma_setup) (struct ata_queued_cmd *qc);
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void (*bmdma_start) (struct ata_queued_cmd *qc);
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</programlisting>
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<para>
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When setting up an IDE BMDMA transaction, these hooks arm
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(->bmdma_setup) and fire (->bmdma_start) the hardware's DMA
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engine.
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</para>
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<programlisting>
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void (*qc_prep) (struct ata_queued_cmd *qc);
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int (*qc_issue) (struct ata_queued_cmd *qc);
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</programlisting>
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<para>
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Higher-level hooks, these two hooks can potentially supercede
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several of the above taskfile/DMA engine hooks. ->qc_prep is
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called after the buffers have been DMA-mapped, and is typically
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used to populate the hardware's DMA scatter-gather table.
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Most drivers use the standard ata_qc_prep() helper function, but
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more advanced drivers roll their own.
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</para>
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<para>
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->qc_issue is used to make a command active, once the hardware
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and S/G tables have been prepared. IDE BMDMA drivers use the
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helper function ata_qc_issue_prot() for taskfile protocol-based
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dispatch. More advanced drivers roll their own ->qc_issue
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implementation, using this as the "issue new ATA command to
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hardware" hook.
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</para>
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<programlisting>
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void (*eng_timeout) (struct ata_port *ap);
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</programlisting>
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<para>
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This is a high level error handling function, called from the
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error handling thread, when a command times out.
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</para>
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<programlisting>
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irqreturn_t (*irq_handler)(int, void *, struct pt_regs *);
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void (*irq_clear) (struct ata_port *);
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</programlisting>
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<para>
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->irq_handler is the interrupt handling routine registered with
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the system, by libata. ->irq_clear is called during probe just
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before the interrupt handler is registered, to be sure hardware
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is quiet.
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</para>
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<programlisting>
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u32 (*scr_read) (struct ata_port *ap, unsigned int sc_reg);
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void (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
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u32 val);
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</programlisting>
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<para>
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Read and write standard SATA phy registers. Currently only used
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if ->phy_reset hook called the sata_phy_reset() helper function.
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</para>
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<programlisting>
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int (*port_start) (struct ata_port *ap);
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void (*port_stop) (struct ata_port *ap);
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void (*host_stop) (struct ata_host_set *host_set);
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</programlisting>
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<para>
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->port_start() is called just after the data structures for each
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port are initialized. Typically this is used to alloc per-port
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DMA buffers / tables / rings, enable DMA engines, and similar
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tasks.
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</para>
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<para>
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->host_stop() is called when the rmmod or hot unplug process
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begins. The hook must stop all hardware interrupts, DMA
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engines, etc.
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</para>
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<para>
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->port_stop() is called after ->host_stop(). It's sole function
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is to release DMA/memory resources, now that they are no longer
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actively being used.
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</para>
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</sect1>
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</chapter>
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<chapter id="libataExt">
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<title>libata Library</title>
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!Edrivers/scsi/libata-core.c
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</chapter>
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<chapter id="libataInt">
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<title>libata Core Internals</title>
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!Idrivers/scsi/libata-core.c
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</chapter>
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<chapter id="libataScsiInt">
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<title>libata SCSI translation/emulation</title>
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!Edrivers/scsi/libata-scsi.c
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!Idrivers/scsi/libata-scsi.c
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</chapter>
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<chapter id="PiixInt">
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<title>ata_piix Internals</title>
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!Idrivers/scsi/ata_piix.c
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</chapter>
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<chapter id="SILInt">
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<title>sata_sil Internals</title>
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!Idrivers/scsi/sata_sil.c
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</chapter>
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</book>
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