[libata] Update docs to reflect current driver API

	</sect2>

	<sect2><title>PIO data read/write</title>

	<programlisting>

void (*data_xfer) (struct ata_device *, unsigned char *, unsigned int, int);

	</programlisting>

	<para>

All bmdma-style drivers must implement this hook.  This is the low-level

operation that actually copies the data bytes during a PIO data

transfer.

Typically the driver

will choose one of ata_pio_data_xfer_noirq(), ata_pio_data_xfer(), or

ata_mmio_data_xfer().

	</para>

	</sect2>

	<sect2><title>ATA command execute</title>

	<programlisting>

void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);

	<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

	Reads the Status/AltStatus 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

	</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);

	</sect2>

	<sect2><title>Timeout (error) handling</title>

	<sect2><title>Exception and probe handling (EH)</title>

	<programlisting>

void (*eng_timeout) (struct ata_port *ap);

void (*phy_reset) (struct ata_port *ap);

	</programlisting>

	<para>

Deprecated.  Use ->error_handler() instead.

	</para>

	<programlisting>

void (*freeze) (struct ata_port *ap);

void (*thaw) (struct ata_port *ap);

	</programlisting>

	<para>

ata_port_freeze() is called when HSM violations or some other

condition disrupts normal operation of the port.  A frozen port

is not allowed to perform any operation until the port is

thawed, which usually follows a successful reset.

	</para>

	<para>

The optional ->freeze() callback can be used for freezing the port

hardware-wise (e.g. mask interrupt and stop DMA engine).  If a

port cannot be frozen hardware-wise, the interrupt handler

must ack and clear interrupts unconditionally while the port

is frozen.

	</para>

	<para>

The optional ->thaw() callback is called to perform the opposite of ->freeze():

prepare the port for normal operation once again.  Unmask interrupts,

start DMA engine, etc.

	</para>

	<programlisting>

void (*error_handler) (struct ata_port *ap);

	</programlisting>

	<para>

->error_handler() is a driver's hook into probe, hotplug, and recovery

and other exceptional conditions.  The primary responsibility of an

implementation is to call ata_do_eh() or ata_bmdma_drive_eh() with a set

of EH hooks as arguments:

	</para>

	<para>

'prereset' hook (may be NULL) is called during an EH reset, before any other actions

are taken.

	</para>

	<para>

'postreset' hook (may be NULL) is called after the EH reset is performed.  Based on

existing conditions, severity of the problem, and hardware capabilities,

	</para>

	<para>

Either 'softreset' (may be NULL) or 'hardreset' (may be NULL) will be

called to perform the low-level EH reset.

	</para>

	<programlisting>

void (*post_internal_cmd) (struct ata_queued_cmd *qc);

	</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().

Perform any hardware-specific actions necessary to finish processing

after executing a probe-time or EH-time command via ata_exec_internal().

	</para>

	</sect2>

/**

 *	ata_mmio_data_xfer - Transfer data by MMIO

 *	@dev: device for this I/O

 *	@adev: device for this I/O

 *	@buf: data buffer

 *	@buflen: buffer length

 *	@write_data: read/write