1 ================================== 1 ==================================
2 GPIO Descriptor Consumer Interface 2 GPIO Descriptor Consumer Interface
3 ================================== 3 ==================================
4 4
5 This document describes the consumer interface !! 5 This document describes the consumer interface of the GPIO framework. Note that
>> 6 it describes the new descriptor-based interface. For a description of the
>> 7 deprecated integer-based GPIO interface please refer to gpio-legacy.txt.
6 8
7 9
8 Guidelines for GPIOs consumers 10 Guidelines for GPIOs consumers
9 ============================== 11 ==============================
10 12
11 Drivers that can't work without standard GPIO 13 Drivers that can't work without standard GPIO calls should have Kconfig entries
12 that depend on GPIOLIB or select GPIOLIB. The 14 that depend on GPIOLIB or select GPIOLIB. The functions that allow a driver to
13 obtain and use GPIOs are available by includin !! 15 obtain and use GPIOs are available by including the following file:
14 16
15 #include <linux/gpio/consumer.h> 17 #include <linux/gpio/consumer.h>
16 18
17 There are static inline stubs for all function 19 There are static inline stubs for all functions in the header file in the case
18 where GPIOLIB is disabled. When these stubs ar 20 where GPIOLIB is disabled. When these stubs are called they will emit
19 warnings. These stubs are used for two use cas 21 warnings. These stubs are used for two use cases:
20 22
21 - Simple compile coverage with e.g. COMPILE_TE 23 - Simple compile coverage with e.g. COMPILE_TEST - it does not matter that
22 the current platform does not enable or sele 24 the current platform does not enable or select GPIOLIB because we are not
23 going to execute the system anyway. 25 going to execute the system anyway.
24 26
25 - Truly optional GPIOLIB support - where the d 27 - Truly optional GPIOLIB support - where the driver does not really make use
26 of the GPIOs on certain compile-time configu 28 of the GPIOs on certain compile-time configurations for certain systems, but
27 will use it under other compile-time configu 29 will use it under other compile-time configurations. In this case the
28 consumer must make sure not to call into the 30 consumer must make sure not to call into these functions, or the user will
29 be met with console warnings that may be per 31 be met with console warnings that may be perceived as intimidating.
30 Combining truly optional GPIOLIB usage with <<
31 ``[devm_]gpiod_get_optional()`` is a *bad id <<
32 error messages. Use the ordinary getter func <<
33 some open coding of error handling should be <<
34 32
35 All the functions that work with the descripto 33 All the functions that work with the descriptor-based GPIO interface are
36 prefixed with ``gpiod_``. The ``gpio_`` prefix 34 prefixed with ``gpiod_``. The ``gpio_`` prefix is used for the legacy
37 interface. No other function in the kernel sho 35 interface. No other function in the kernel should use these prefixes. The use
38 of the legacy functions is strongly discourage 36 of the legacy functions is strongly discouraged, new code should use
39 <linux/gpio/consumer.h> and descriptors exclus 37 <linux/gpio/consumer.h> and descriptors exclusively.
40 38
41 39
42 Obtaining and Disposing GPIOs 40 Obtaining and Disposing GPIOs
43 ============================= 41 =============================
44 42
45 With the descriptor-based interface, GPIOs are 43 With the descriptor-based interface, GPIOs are identified with an opaque,
46 non-forgeable handler that must be obtained th 44 non-forgeable handler that must be obtained through a call to one of the
47 gpiod_get() functions. Like many other kernel 45 gpiod_get() functions. Like many other kernel subsystems, gpiod_get() takes the
48 device that will use the GPIO and the function 46 device that will use the GPIO and the function the requested GPIO is supposed to
49 fulfill:: 47 fulfill::
50 48
51 struct gpio_desc *gpiod_get(struct dev 49 struct gpio_desc *gpiod_get(struct device *dev, const char *con_id,
52 enum gpiod 50 enum gpiod_flags flags)
53 51
54 If a function is implemented by using several 52 If a function is implemented by using several GPIOs together (e.g. a simple LED
55 device that displays digits), an additional in 53 device that displays digits), an additional index argument can be specified::
56 54
57 struct gpio_desc *gpiod_get_index(stru 55 struct gpio_desc *gpiod_get_index(struct device *dev,
58 cons 56 const char *con_id, unsigned int idx,
59 enum 57 enum gpiod_flags flags)
60 58
61 For a more detailed description of the con_id 59 For a more detailed description of the con_id parameter in the DeviceTree case
62 see Documentation/driver-api/gpio/board.rst 60 see Documentation/driver-api/gpio/board.rst
63 61
64 The flags parameter is used to optionally spec 62 The flags parameter is used to optionally specify a direction and initial value
65 for the GPIO. Values can be: 63 for the GPIO. Values can be:
66 64
67 * GPIOD_ASIS or 0 to not initialize the GPIO a 65 * GPIOD_ASIS or 0 to not initialize the GPIO at all. The direction must be set
68 later with one of the dedicated functions. 66 later with one of the dedicated functions.
69 * GPIOD_IN to initialize the GPIO as input. 67 * GPIOD_IN to initialize the GPIO as input.
70 * GPIOD_OUT_LOW to initialize the GPIO as outp 68 * GPIOD_OUT_LOW to initialize the GPIO as output with a value of 0.
71 * GPIOD_OUT_HIGH to initialize the GPIO as out 69 * GPIOD_OUT_HIGH to initialize the GPIO as output with a value of 1.
72 * GPIOD_OUT_LOW_OPEN_DRAIN same as GPIOD_OUT_L 70 * GPIOD_OUT_LOW_OPEN_DRAIN same as GPIOD_OUT_LOW but also enforce the line
73 to be electrically used with open drain. 71 to be electrically used with open drain.
74 * GPIOD_OUT_HIGH_OPEN_DRAIN same as GPIOD_OUT_ 72 * GPIOD_OUT_HIGH_OPEN_DRAIN same as GPIOD_OUT_HIGH but also enforce the line
75 to be electrically used with open drain. 73 to be electrically used with open drain.
76 74
77 Note that the initial value is *logical* and t <<
78 whether the line is configured active high or <<
79 :ref:`active_low_semantics`). <<
80 <<
81 The two last flags are used for use cases wher 75 The two last flags are used for use cases where open drain is mandatory, such
82 as I2C: if the line is not already configured 76 as I2C: if the line is not already configured as open drain in the mappings
83 (see board.rst), then open drain will be enfor !! 77 (see board.txt), then open drain will be enforced anyway and a warning will be
84 printed that the board configuration needs to 78 printed that the board configuration needs to be updated to match the use case.
85 79
86 Both functions return either a valid GPIO desc 80 Both functions return either a valid GPIO descriptor, or an error code checkable
87 with IS_ERR() (they will never return a NULL p 81 with IS_ERR() (they will never return a NULL pointer). -ENOENT will be returned
88 if and only if no GPIO has been assigned to th 82 if and only if no GPIO has been assigned to the device/function/index triplet,
89 other error codes are used for cases where a G 83 other error codes are used for cases where a GPIO has been assigned but an error
90 occurred while trying to acquire it. This is u 84 occurred while trying to acquire it. This is useful to discriminate between mere
91 errors and an absence of GPIO for optional GPI 85 errors and an absence of GPIO for optional GPIO parameters. For the common
92 pattern where a GPIO is optional, the gpiod_ge 86 pattern where a GPIO is optional, the gpiod_get_optional() and
93 gpiod_get_index_optional() functions can be us 87 gpiod_get_index_optional() functions can be used. These functions return NULL
94 instead of -ENOENT if no GPIO has been assigne 88 instead of -ENOENT if no GPIO has been assigned to the requested function::
95 89
96 struct gpio_desc *gpiod_get_optional(s 90 struct gpio_desc *gpiod_get_optional(struct device *dev,
97 c 91 const char *con_id,
98 e 92 enum gpiod_flags flags)
99 93
100 struct gpio_desc *gpiod_get_index_opti 94 struct gpio_desc *gpiod_get_index_optional(struct device *dev,
101 95 const char *con_id,
102 96 unsigned int index,
103 97 enum gpiod_flags flags)
104 98
105 Note that gpio_get*_optional() functions (and 99 Note that gpio_get*_optional() functions (and their managed variants), unlike
106 the rest of gpiolib API, also return NULL when 100 the rest of gpiolib API, also return NULL when gpiolib support is disabled.
107 This is helpful to driver authors, since they 101 This is helpful to driver authors, since they do not need to special case
108 -ENOSYS return codes. System integrators shou 102 -ENOSYS return codes. System integrators should however be careful to enable
109 gpiolib on systems that need it. 103 gpiolib on systems that need it.
110 104
111 For a function using multiple GPIOs all of tho 105 For a function using multiple GPIOs all of those can be obtained with one call::
112 106
113 struct gpio_descs *gpiod_get_array(str 107 struct gpio_descs *gpiod_get_array(struct device *dev,
114 con 108 const char *con_id,
115 enu 109 enum gpiod_flags flags)
116 110
117 This function returns a struct gpio_descs whic 111 This function returns a struct gpio_descs which contains an array of
118 descriptors. It also contains a pointer to a !! 112 descriptors::
119 if passed back to get/set array functions, may <<
120 113
121 struct gpio_descs { 114 struct gpio_descs {
122 struct gpio_array *info; <<
123 unsigned int ndescs; 115 unsigned int ndescs;
124 struct gpio_desc *desc[]; 116 struct gpio_desc *desc[];
125 } 117 }
126 118
127 The following function returns NULL instead of 119 The following function returns NULL instead of -ENOENT if no GPIOs have been
128 assigned to the requested function:: 120 assigned to the requested function::
129 121
130 struct gpio_descs *gpiod_get_array_opt 122 struct gpio_descs *gpiod_get_array_optional(struct device *dev,
131 123 const char *con_id,
132 124 enum gpiod_flags flags)
133 125
134 Device-managed variants of these functions are 126 Device-managed variants of these functions are also defined::
135 127
136 struct gpio_desc *devm_gpiod_get(struc 128 struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id,
137 enum 129 enum gpiod_flags flags)
138 130
139 struct gpio_desc *devm_gpiod_get_index 131 struct gpio_desc *devm_gpiod_get_index(struct device *dev,
140 132 const char *con_id,
141 133 unsigned int idx,
142 134 enum gpiod_flags flags)
143 135
144 struct gpio_desc *devm_gpiod_get_optio 136 struct gpio_desc *devm_gpiod_get_optional(struct device *dev,
145 137 const char *con_id,
146 138 enum gpiod_flags flags)
147 139
148 struct gpio_desc *devm_gpiod_get_index 140 struct gpio_desc *devm_gpiod_get_index_optional(struct device *dev,
149 141 const char *con_id,
150 142 unsigned int index,
151 143 enum gpiod_flags flags)
152 144
153 struct gpio_descs *devm_gpiod_get_arra 145 struct gpio_descs *devm_gpiod_get_array(struct device *dev,
154 146 const char *con_id,
155 147 enum gpiod_flags flags)
156 148
157 struct gpio_descs *devm_gpiod_get_arra 149 struct gpio_descs *devm_gpiod_get_array_optional(struct device *dev,
158 150 const char *con_id,
159 151 enum gpiod_flags flags)
160 152
161 A GPIO descriptor can be disposed of using the 153 A GPIO descriptor can be disposed of using the gpiod_put() function::
162 154
163 void gpiod_put(struct gpio_desc *desc) 155 void gpiod_put(struct gpio_desc *desc)
164 156
165 For an array of GPIOs this function can be use 157 For an array of GPIOs this function can be used::
166 158
167 void gpiod_put_array(struct gpio_descs 159 void gpiod_put_array(struct gpio_descs *descs)
168 160
169 It is strictly forbidden to use a descriptor a 161 It is strictly forbidden to use a descriptor after calling these functions.
170 It is also not allowed to individually release 162 It is also not allowed to individually release descriptors (using gpiod_put())
171 from an array acquired with gpiod_get_array(). 163 from an array acquired with gpiod_get_array().
172 164
173 The device-managed variants are, unsurprisingl 165 The device-managed variants are, unsurprisingly::
174 166
175 void devm_gpiod_put(struct device *dev 167 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
176 168
177 void devm_gpiod_put_array(struct devic 169 void devm_gpiod_put_array(struct device *dev, struct gpio_descs *descs)
178 170
179 171
180 Using GPIOs 172 Using GPIOs
181 =========== 173 ===========
182 174
183 Setting Direction 175 Setting Direction
184 ----------------- 176 -----------------
185 The first thing a driver must do with a GPIO i 177 The first thing a driver must do with a GPIO is setting its direction. If no
186 direction-setting flags have been given to gpi 178 direction-setting flags have been given to gpiod_get*(), this is done by
187 invoking one of the gpiod_direction_*() functi 179 invoking one of the gpiod_direction_*() functions::
188 180
189 int gpiod_direction_input(struct gpio_ 181 int gpiod_direction_input(struct gpio_desc *desc)
190 int gpiod_direction_output(struct gpio 182 int gpiod_direction_output(struct gpio_desc *desc, int value)
191 183
192 The return value is zero for success, else a n 184 The return value is zero for success, else a negative errno. It should be
193 checked, since the get/set calls don't return 185 checked, since the get/set calls don't return errors and since misconfiguration
194 is possible. You should normally issue these c 186 is possible. You should normally issue these calls from a task context. However,
195 for spinlock-safe GPIOs it is OK to use them b 187 for spinlock-safe GPIOs it is OK to use them before tasking is enabled, as part
196 of early board setup. 188 of early board setup.
197 189
198 For output GPIOs, the value provided becomes t 190 For output GPIOs, the value provided becomes the initial output value. This
199 helps avoid signal glitching during system sta 191 helps avoid signal glitching during system startup.
200 192
201 A driver can also query the current direction 193 A driver can also query the current direction of a GPIO::
202 194
203 int gpiod_get_direction(const struct g 195 int gpiod_get_direction(const struct gpio_desc *desc)
204 196
205 This function returns 0 for output, 1 for inpu 197 This function returns 0 for output, 1 for input, or an error code in case of error.
206 198
207 Be aware that there is no default direction fo 199 Be aware that there is no default direction for GPIOs. Therefore, **using a GPIO
208 without setting its direction first is illegal 200 without setting its direction first is illegal and will result in undefined
209 behavior!** 201 behavior!**
210 202
211 203
212 Spinlock-Safe GPIO Access 204 Spinlock-Safe GPIO Access
213 ------------------------- 205 -------------------------
214 Most GPIO controllers can be accessed with mem 206 Most GPIO controllers can be accessed with memory read/write instructions. Those
215 don't need to sleep, and can safely be done fr 207 don't need to sleep, and can safely be done from inside hard (non-threaded) IRQ
216 handlers and similar contexts. 208 handlers and similar contexts.
217 209
218 Use the following calls to access GPIOs from a 210 Use the following calls to access GPIOs from an atomic context::
219 211
220 int gpiod_get_value(const struct gpio_ 212 int gpiod_get_value(const struct gpio_desc *desc);
221 void gpiod_set_value(struct gpio_desc 213 void gpiod_set_value(struct gpio_desc *desc, int value);
222 214
223 The values are boolean, zero for inactive, non !! 215 The values are boolean, zero for low, nonzero for high. When reading the value
224 value of an output pin, the value returned sho !! 216 of an output pin, the value returned should be what's seen on the pin. That
225 That won't always match the specified output v !! 217 won't always match the specified output value, because of issues including
226 open-drain signaling and output latencies. 218 open-drain signaling and output latencies.
227 219
228 The get/set calls do not return errors because 220 The get/set calls do not return errors because "invalid GPIO" should have been
229 reported earlier from gpiod_direction_*(). How 221 reported earlier from gpiod_direction_*(). However, note that not all platforms
230 can read the value of output pins; those that 222 can read the value of output pins; those that can't should always return zero.
231 Also, using these calls for GPIOs that can't s 223 Also, using these calls for GPIOs that can't safely be accessed without sleeping
232 (see below) is an error. 224 (see below) is an error.
233 225
234 226
235 GPIO Access That May Sleep 227 GPIO Access That May Sleep
236 -------------------------- 228 --------------------------
237 Some GPIO controllers must be accessed using m 229 Some GPIO controllers must be accessed using message based buses like I2C or
238 SPI. Commands to read or write those GPIO valu 230 SPI. Commands to read or write those GPIO values require waiting to get to the
239 head of a queue to transmit a command and get 231 head of a queue to transmit a command and get its response. This requires
240 sleeping, which can't be done from inside IRQ 232 sleeping, which can't be done from inside IRQ handlers.
241 233
242 Platforms that support this type of GPIO disti 234 Platforms that support this type of GPIO distinguish them from other GPIOs by
243 returning nonzero from this call:: 235 returning nonzero from this call::
244 236
245 int gpiod_cansleep(const struct gpio_d 237 int gpiod_cansleep(const struct gpio_desc *desc)
246 238
247 To access such GPIOs, a different set of acces 239 To access such GPIOs, a different set of accessors is defined::
248 240
249 int gpiod_get_value_cansleep(const str 241 int gpiod_get_value_cansleep(const struct gpio_desc *desc)
250 void gpiod_set_value_cansleep(struct g 242 void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
251 243
252 Accessing such GPIOs requires a context which 244 Accessing such GPIOs requires a context which may sleep, for example a threaded
253 IRQ handler, and those accessors must be used 245 IRQ handler, and those accessors must be used instead of spinlock-safe
254 accessors without the cansleep() name suffix. 246 accessors without the cansleep() name suffix.
255 247
256 Other than the fact that these accessors might 248 Other than the fact that these accessors might sleep, and will work on GPIOs
257 that can't be accessed from hardIRQ handlers, 249 that can't be accessed from hardIRQ handlers, these calls act the same as the
258 spinlock-safe calls. 250 spinlock-safe calls.
259 251
260 252
261 .. _active_low_semantics: <<
262 <<
263 The active low and open drain semantics 253 The active low and open drain semantics
264 --------------------------------------- 254 ---------------------------------------
265 As a consumer should not have to care about th 255 As a consumer should not have to care about the physical line level, all of the
266 gpiod_set_value_xxx() or gpiod_set_array_value 256 gpiod_set_value_xxx() or gpiod_set_array_value_xxx() functions operate with
267 the *logical* value. With this they take the a 257 the *logical* value. With this they take the active low property into account.
268 This means that they check whether the GPIO is 258 This means that they check whether the GPIO is configured to be active low,
269 and if so, they manipulate the passed value be 259 and if so, they manipulate the passed value before the physical line level is
270 driven. 260 driven.
271 261
272 The same is applicable for open drain or open 262 The same is applicable for open drain or open source output lines: those do not
273 actively drive their output high (open drain) 263 actively drive their output high (open drain) or low (open source), they just
274 switch their output to a high impedance value. 264 switch their output to a high impedance value. The consumer should not need to
275 care. (For details read about open drain in dr !! 265 care. (For details read about open drain in driver.txt.)
276 266
277 With this, all the gpiod_set_(array)_value_xxx 267 With this, all the gpiod_set_(array)_value_xxx() functions interpret the
278 parameter "value" as "active" ("1") or "inacti !! 268 parameter "value" as "asserted" ("1") or "de-asserted" ("0"). The physical line
279 level will be driven accordingly. 269 level will be driven accordingly.
280 270
281 As an example, if the active low property for 271 As an example, if the active low property for a dedicated GPIO is set, and the
282 gpiod_set_(array)_value_xxx() passes "active" !! 272 gpiod_set_(array)_value_xxx() passes "asserted" ("1"), the physical line level
283 will be driven low. 273 will be driven low.
284 274
285 To summarize:: 275 To summarize::
286 276
287 Function (example) line prop 277 Function (example) line property physical line
288 gpiod_set_raw_value(desc, 0); don't car 278 gpiod_set_raw_value(desc, 0); don't care low
289 gpiod_set_raw_value(desc, 1); don't car 279 gpiod_set_raw_value(desc, 1); don't care high
290 gpiod_set_value(desc, 0); default ( 280 gpiod_set_value(desc, 0); default (active high) low
291 gpiod_set_value(desc, 1); default ( 281 gpiod_set_value(desc, 1); default (active high) high
292 gpiod_set_value(desc, 0); active lo 282 gpiod_set_value(desc, 0); active low high
293 gpiod_set_value(desc, 1); active lo 283 gpiod_set_value(desc, 1); active low low
>> 284 gpiod_set_value(desc, 0); default (active high) low
>> 285 gpiod_set_value(desc, 1); default (active high) high
294 gpiod_set_value(desc, 0); open drai 286 gpiod_set_value(desc, 0); open drain low
295 gpiod_set_value(desc, 1); open drai 287 gpiod_set_value(desc, 1); open drain high impedance
296 gpiod_set_value(desc, 0); open sour 288 gpiod_set_value(desc, 0); open source high impedance
297 gpiod_set_value(desc, 1); open sour 289 gpiod_set_value(desc, 1); open source high
298 290
299 It is possible to override these semantics usi 291 It is possible to override these semantics using the set_raw/get_raw functions
300 but it should be avoided as much as possible, 292 but it should be avoided as much as possible, especially by system-agnostic drivers
301 which should not need to care about the actual 293 which should not need to care about the actual physical line level and worry about
302 the logical value instead. 294 the logical value instead.
303 295
304 296
305 Accessing raw GPIO values 297 Accessing raw GPIO values
306 ------------------------- 298 -------------------------
307 Consumers exist that need to manage the logica 299 Consumers exist that need to manage the logical state of a GPIO line, i.e. the value
308 their device will actually receive, no matter 300 their device will actually receive, no matter what lies between it and the GPIO
309 line. 301 line.
310 302
311 The following set of calls ignore the active-l 303 The following set of calls ignore the active-low or open drain property of a GPIO and
312 work on the raw line value:: 304 work on the raw line value::
313 305
314 int gpiod_get_raw_value(const struct g 306 int gpiod_get_raw_value(const struct gpio_desc *desc)
315 void gpiod_set_raw_value(struct gpio_d 307 void gpiod_set_raw_value(struct gpio_desc *desc, int value)
316 int gpiod_get_raw_value_cansleep(const 308 int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc)
317 void gpiod_set_raw_value_cansleep(stru 309 void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value)
318 int gpiod_direction_output_raw(struct 310 int gpiod_direction_output_raw(struct gpio_desc *desc, int value)
319 311
320 The active low state of a GPIO can also be que !! 312 The active low state of a GPIO can also be queried using the following call::
321 following calls:: <<
322 313
323 int gpiod_is_active_low(const struct g 314 int gpiod_is_active_low(const struct gpio_desc *desc)
324 void gpiod_toggle_active_low(struct gp <<
325 315
326 Note that these functions should only be used 316 Note that these functions should only be used with great moderation; a driver
327 should not have to care about the physical lin 317 should not have to care about the physical line level or open drain semantics.
328 318
329 319
330 Access multiple GPIOs with a single function c 320 Access multiple GPIOs with a single function call
331 ---------------------------------------------- 321 -------------------------------------------------
332 The following functions get or set the values 322 The following functions get or set the values of an array of GPIOs::
333 323
334 int gpiod_get_array_value(unsigned int 324 int gpiod_get_array_value(unsigned int array_size,
335 struct gpio_ 325 struct gpio_desc **desc_array,
336 struct gpio_ !! 326 int *value_array);
337 unsigned lon <<
338 int gpiod_get_raw_array_value(unsigned 327 int gpiod_get_raw_array_value(unsigned int array_size,
339 struct g 328 struct gpio_desc **desc_array,
340 struct g !! 329 int *value_array);
341 unsigned <<
342 int gpiod_get_array_value_cansleep(uns 330 int gpiod_get_array_value_cansleep(unsigned int array_size,
343 str 331 struct gpio_desc **desc_array,
344 str !! 332 int *value_array);
345 uns <<
346 int gpiod_get_raw_array_value_cansleep 333 int gpiod_get_raw_array_value_cansleep(unsigned int array_size,
347 str 334 struct gpio_desc **desc_array,
348 str !! 335 int *value_array);
349 uns <<
350 336
351 int gpiod_set_array_value(unsigned int !! 337 void gpiod_set_array_value(unsigned int array_size,
352 struct gpio_ !! 338 struct gpio_desc **desc_array,
353 struct gpio_ !! 339 int *value_array)
354 unsigned lon !! 340 void gpiod_set_raw_array_value(unsigned int array_size,
355 int gpiod_set_raw_array_value(unsigned !! 341 struct gpio_desc **desc_array,
356 struct g !! 342 int *value_array)
357 struct g !! 343 void gpiod_set_array_value_cansleep(unsigned int array_size,
358 unsigned !! 344 struct gpio_desc **desc_array,
359 int gpiod_set_array_value_cansleep(uns !! 345 int *value_array)
360 str !! 346 void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
361 str !! 347 struct gpio_desc **desc_array,
362 uns !! 348 int *value_array)
363 int gpiod_set_raw_array_value_cansleep <<
364 <<
365 <<
366 <<
367 349
368 The array can be an arbitrary set of GPIOs. Th 350 The array can be an arbitrary set of GPIOs. The functions will try to access
369 GPIOs belonging to the same bank or chip simul 351 GPIOs belonging to the same bank or chip simultaneously if supported by the
370 corresponding chip driver. In that case a sign 352 corresponding chip driver. In that case a significantly improved performance
371 can be expected. If simultaneous access is not 353 can be expected. If simultaneous access is not possible the GPIOs will be
372 accessed sequentially. 354 accessed sequentially.
373 355
374 The functions take four arguments: !! 356 The functions take three arguments:
375 <<
376 * array_size - the number of array 357 * array_size - the number of array elements
377 * desc_array - an array of GPIO des 358 * desc_array - an array of GPIO descriptors
378 * array_info - optional information !! 359 * value_array - an array to store the GPIOs' values (get) or
379 * value_bitmap - a bitmap to store th !! 360 an array of values to assign to the GPIOs (set)
380 a bitmap of values to assign to the <<
381 361
382 The descriptor array can be obtained using the 362 The descriptor array can be obtained using the gpiod_get_array() function
383 or one of its variants. If the group of descri 363 or one of its variants. If the group of descriptors returned by that function
384 matches the desired group of GPIOs, those GPIO 364 matches the desired group of GPIOs, those GPIOs can be accessed by simply using
385 the struct gpio_descs returned by gpiod_get_ar 365 the struct gpio_descs returned by gpiod_get_array()::
386 366
387 struct gpio_descs *my_gpio_descs = gpi 367 struct gpio_descs *my_gpio_descs = gpiod_get_array(...);
388 gpiod_set_array_value(my_gpio_descs->n 368 gpiod_set_array_value(my_gpio_descs->ndescs, my_gpio_descs->desc,
389 my_gpio_descs->i !! 369 my_gpio_values);
390 370
391 It is also possible to access a completely arb 371 It is also possible to access a completely arbitrary array of descriptors. The
392 descriptors may be obtained using any combinat 372 descriptors may be obtained using any combination of gpiod_get() and
393 gpiod_get_array(). Afterwards the array of des 373 gpiod_get_array(). Afterwards the array of descriptors has to be setup
394 manually before it can be passed to one of the !! 374 manually before it can be passed to one of the above functions.
395 array_info should be set to NULL. <<
396 375
397 Note that for optimal performance GPIOs belong 376 Note that for optimal performance GPIOs belonging to the same chip should be
398 contiguous within the array of descriptors. 377 contiguous within the array of descriptors.
399 378
400 Still better performance may be achieved if ar <<
401 match hardware pin numbers of a single chip. <<
402 array function matches the one obtained from g <<
403 associated with the array is also passed, the <<
404 processing path, passing the value_bitmap argu <<
405 .get/set_multiple() callback of the chip. Tha <<
406 banks as data I/O ports without much loss of p <<
407 <<
408 The return value of gpiod_get_array_value() an 379 The return value of gpiod_get_array_value() and its variants is 0 on success
409 or negative on error. Note the difference to g 380 or negative on error. Note the difference to gpiod_get_value(), which returns
410 0 or 1 on success to convey the GPIO value. Wi 381 0 or 1 on success to convey the GPIO value. With the array functions, the GPIO
411 values are stored in value_array rather than p 382 values are stored in value_array rather than passed back as return value.
412 383
413 384
414 GPIOs mapped to IRQs 385 GPIOs mapped to IRQs
415 -------------------- 386 --------------------
416 GPIO lines can quite often be used as IRQs. Yo 387 GPIO lines can quite often be used as IRQs. You can get the IRQ number
417 corresponding to a given GPIO using the follow 388 corresponding to a given GPIO using the following call::
418 389
419 int gpiod_to_irq(const struct gpio_des 390 int gpiod_to_irq(const struct gpio_desc *desc)
420 391
421 It will return an IRQ number, or a negative er 392 It will return an IRQ number, or a negative errno code if the mapping can't be
422 done (most likely because that particular GPIO 393 done (most likely because that particular GPIO cannot be used as IRQ). It is an
423 unchecked error to use a GPIO that wasn't set 394 unchecked error to use a GPIO that wasn't set up as an input using
424 gpiod_direction_input(), or to use an IRQ numb 395 gpiod_direction_input(), or to use an IRQ number that didn't originally come
425 from gpiod_to_irq(). gpiod_to_irq() is not all 396 from gpiod_to_irq(). gpiod_to_irq() is not allowed to sleep.
426 397
427 Non-error values returned from gpiod_to_irq() 398 Non-error values returned from gpiod_to_irq() can be passed to request_irq() or
428 free_irq(). They will often be stored into IRQ 399 free_irq(). They will often be stored into IRQ resources for platform devices,
429 by the board-specific initialization code. Not 400 by the board-specific initialization code. Note that IRQ trigger options are
430 part of the IRQ interface, e.g. IRQF_TRIGGER_F 401 part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are system wakeup
431 capabilities. 402 capabilities.
432 403
433 404
434 GPIOs and ACPI 405 GPIOs and ACPI
435 ============== 406 ==============
436 407
437 On ACPI systems, GPIOs are described by GpioIo 408 On ACPI systems, GPIOs are described by GpioIo()/GpioInt() resources listed by
438 the _CRS configuration objects of devices. Th 409 the _CRS configuration objects of devices. Those resources do not provide
439 connection IDs (names) for GPIOs, so it is nec 410 connection IDs (names) for GPIOs, so it is necessary to use an additional
440 mechanism for this purpose. 411 mechanism for this purpose.
441 412
442 Systems compliant with ACPI 5.1 or newer may p 413 Systems compliant with ACPI 5.1 or newer may provide a _DSD configuration object
443 which, among other things, may be used to prov 414 which, among other things, may be used to provide connection IDs for specific
444 GPIOs described by the GpioIo()/GpioInt() reso 415 GPIOs described by the GpioIo()/GpioInt() resources in _CRS. If that is the
445 case, it will be handled by the GPIO subsystem 416 case, it will be handled by the GPIO subsystem automatically. However, if the
446 _DSD is not present, the mappings between Gpio 417 _DSD is not present, the mappings between GpioIo()/GpioInt() resources and GPIO
447 connection IDs need to be provided by device d 418 connection IDs need to be provided by device drivers.
448 419
449 For details refer to Documentation/firmware-gu !! 420 For details refer to Documentation/acpi/gpio-properties.txt
450 421
451 422
452 Interacting With the Legacy GPIO Subsystem 423 Interacting With the Legacy GPIO Subsystem
453 ========================================== 424 ==========================================
454 Many kernel subsystems and drivers still handl !! 425 Many kernel subsystems still handle GPIOs using the legacy integer-based
455 integer-based interface. It is strongly recomm !! 426 interface. Although it is strongly encouraged to upgrade them to the safer
456 gpiod interface. For cases where both interfac !! 427 descriptor-based API, the following two functions allow you to convert a GPIO
457 two functions allow to convert a GPIO descript !! 428 descriptor into the GPIO integer namespace and vice-versa::
458 and vice-versa:: <<
459 429
460 int desc_to_gpio(const struct gpio_des 430 int desc_to_gpio(const struct gpio_desc *desc)
461 struct gpio_desc *gpio_to_desc(unsigne 431 struct gpio_desc *gpio_to_desc(unsigned gpio)
462 432
463 The GPIO number returned by desc_to_gpio() can !! 433 The GPIO number returned by desc_to_gpio() can be safely used as long as the
464 the gpio\_*() functions for as long as the GPI !! 434 GPIO descriptor has not been freed. All the same, a GPIO number passed to
465 All the same, a GPIO number passed to gpio_to_ !! 435 gpio_to_desc() must have been properly acquired, and usage of the returned GPIO
466 acquired using e.g. gpio_request_one(), and th !! 436 descriptor is only possible after the GPIO number has been released.
467 considered valid until that GPIO number is rel <<
468 437
469 Freeing a GPIO obtained by one API with the ot 438 Freeing a GPIO obtained by one API with the other API is forbidden and an
470 unchecked error. 439 unchecked error.
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