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" []>
5 <book id="libataDevGuide">
7 <title>libATA Developer's Guide</title>
11 <firstname>Jeff</firstname>
12 <surname>Garzik</surname>
17 <year>2003-2005</year>
18 <holder>Jeff Garzik</holder>
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
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.
47 <chapter id="libataIntroduction">
48 <title>Introduction</title>
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.
56 This Guide documents the libATA driver API, library functions, library
57 internals, and a couple sample ATA low-level drivers.
61 <chapter id="libataThanks">
64 The bulk of the ATA knowledge comes thanks to long conversations with
65 Andre Hedrick (www.linux-ide.org), and long hours pondering the ATA
66 and SCSI specifications.
69 Thanks to Alan Cox for pointing out similarities
70 between SATA and SCSI, and in general for motivation to hack on
74 libata's device detection
75 method, ata_pio_devchk, and in general all the early probing was
76 based on extensive study of Hale Landis's probe/reset code in his
77 ATADRVR driver (www.ata-atapi.com).
81 <chapter id="libataDriverApi">
82 <title>libata Driver API</title>
84 <title>struct ata_port_operations</title>
87 void (*port_disable) (struct ata_port *);
91 Called from ata_bus_probe() and ata_bus_reset() error paths,
92 as well as when unregistering from the SCSI module (rmmod, hot
97 void (*dev_config) (struct ata_port *, struct ata_device *);
101 Called after IDENTIFY [PACKET] DEVICE is issued to each device
102 found. Typically used to apply device-specific fixups prior to
103 issue of SET FEATURES - XFER MODE, and prior to operation.
107 void (*set_piomode) (struct ata_port *, struct ata_device *);
108 void (*set_dmamode) (struct ata_port *, struct ata_device *);
109 void (*post_set_mode) (struct ata_port *ap);
113 Hooks called prior to the issue of SET FEATURES - XFER MODE
114 command. dev->pio_mode is guaranteed to be valid when
115 ->set_piomode() is called, and dev->dma_mode is guaranteed to be
116 valid when ->set_dmamode() is called. ->post_set_mode() is
117 called unconditionally, after the SET FEATURES - XFER MODE
118 command completes successfully.
122 ->set_piomode() is always called (if present), but
123 ->set_dma_mode() is only called if DMA is possible.
127 void (*tf_load) (struct ata_port *ap, struct ata_taskfile *tf);
128 void (*tf_read) (struct ata_port *ap, struct ata_taskfile *tf);
132 ->tf_load() is called to load the given taskfile into hardware
133 registers / DMA buffers. ->tf_read() is called to read the
134 hardware registers / DMA buffers, to obtain the current set of
135 taskfile register values.
139 void (*exec_command)(struct ata_port *ap, struct ata_taskfile *tf);
143 causes an ATA command, previously loaded with
144 ->tf_load(), to be initiated in hardware.
148 int (*check_atapi_dma) (struct ata_queued_cmd *qc);
152 Allow low-level driver to filter ATA PACKET commands, returning a status
153 indicating whether or not it is OK to use DMA for the supplied PACKET
158 u8 (*check_status)(struct ata_port *ap);
159 u8 (*check_altstatus)(struct ata_port *ap);
160 u8 (*check_err)(struct ata_port *ap);
164 Reads the Status/AltStatus/Error ATA shadow register from
165 hardware. On some hardware, reading the Status register has
166 the side effect of clearing the interrupt condition.
170 void (*dev_select)(struct ata_port *ap, unsigned int device);
174 Issues the low-level hardware command(s) that causes one of N
175 hardware devices to be considered 'selected' (active and
176 available for use) on the ATA bus. This generally has no
177 meaning on FIS-based devices.
181 void (*phy_reset) (struct ata_port *ap);
185 The very first step in the probe phase. Actions vary depending
186 on the bus type, typically. After waking up the device and probing
187 for device presence (PATA and SATA), typically a soft reset
188 (SRST) will be performed. Drivers typically use the helper
189 functions ata_bus_reset() or sata_phy_reset() for this hook.
193 void (*bmdma_setup) (struct ata_queued_cmd *qc);
194 void (*bmdma_start) (struct ata_queued_cmd *qc);
195 void (*bmdma_stop) (struct ata_port *ap);
196 u8 (*bmdma_status) (struct ata_port *ap);
200 When setting up an IDE BMDMA transaction, these hooks arm
201 (->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop)
202 the hardware's DMA engine. ->bmdma_status is used to read the standard
203 PCI IDE DMA Status register.
207 These hooks are typically either no-ops, or simply not implemented, in
212 void (*qc_prep) (struct ata_queued_cmd *qc);
213 int (*qc_issue) (struct ata_queued_cmd *qc);
217 Higher-level hooks, these two hooks can potentially supercede
218 several of the above taskfile/DMA engine hooks. ->qc_prep is
219 called after the buffers have been DMA-mapped, and is typically
220 used to populate the hardware's DMA scatter-gather table.
221 Most drivers use the standard ata_qc_prep() helper function, but
222 more advanced drivers roll their own.
225 ->qc_issue is used to make a command active, once the hardware
226 and S/G tables have been prepared. IDE BMDMA drivers use the
227 helper function ata_qc_issue_prot() for taskfile protocol-based
228 dispatch. More advanced drivers implement their own ->qc_issue.
232 void (*eng_timeout) (struct ata_port *ap);
236 This is a high level error handling function, called from the
237 error handling thread, when a command times out. Most newer
238 hardware will implement its own error handling code here. IDE BMDMA
239 drivers may use the helper function ata_eng_timeout().
243 irqreturn_t (*irq_handler)(int, void *, struct pt_regs *);
244 void (*irq_clear) (struct ata_port *);
248 ->irq_handler is the interrupt handling routine registered with
249 the system, by libata. ->irq_clear is called during probe just
250 before the interrupt handler is registered, to be sure hardware
255 u32 (*scr_read) (struct ata_port *ap, unsigned int sc_reg);
256 void (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
261 Read and write standard SATA phy registers. Currently only used
262 if ->phy_reset hook called the sata_phy_reset() helper function.
266 int (*port_start) (struct ata_port *ap);
267 void (*port_stop) (struct ata_port *ap);
268 void (*host_stop) (struct ata_host_set *host_set);
272 ->port_start() is called just after the data structures for each
273 port are initialized. Typically this is used to alloc per-port
274 DMA buffers / tables / rings, enable DMA engines, and similar
278 ->port_stop() is called after ->host_stop(). It's sole function
279 is to release DMA/memory resources, now that they are no longer
283 ->host_stop() is called after all ->port_stop() calls
284 have completed. The hook must finalize hardware shutdown, release DMA
285 and other resources, etc.
291 <chapter id="libataExt">
292 <title>libata Library</title>
293 !Edrivers/scsi/libata-core.c
296 <chapter id="libataInt">
297 <title>libata Core Internals</title>
298 !Idrivers/scsi/libata-core.c
301 <chapter id="libataScsiInt">
302 <title>libata SCSI translation/emulation</title>
303 !Edrivers/scsi/libata-scsi.c
304 !Idrivers/scsi/libata-scsi.c
307 <chapter id="PiixInt">
308 <title>ata_piix Internals</title>
309 !Idrivers/scsi/ata_piix.c
312 <chapter id="SILInt">
313 <title>sata_sil Internals</title>
314 !Idrivers/scsi/sata_sil.c