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. It also contains a pointer to a gpiolib private structure which,
119 if passed back to get/set array functions, may !! 113 if passed back to get/set array functions, may speed up I/O proocessing::
120 114
121 struct gpio_descs { 115 struct gpio_descs {
122 struct gpio_array *info; 116 struct gpio_array *info;
123 unsigned int ndescs; 117 unsigned int ndescs;
124 struct gpio_desc *desc[]; 118 struct gpio_desc *desc[];
125 } 119 }
126 120
127 The following function returns NULL instead of 121 The following function returns NULL instead of -ENOENT if no GPIOs have been
128 assigned to the requested function:: 122 assigned to the requested function::
129 123
130 struct gpio_descs *gpiod_get_array_opt 124 struct gpio_descs *gpiod_get_array_optional(struct device *dev,
131 125 const char *con_id,
132 126 enum gpiod_flags flags)
133 127
134 Device-managed variants of these functions are 128 Device-managed variants of these functions are also defined::
135 129
136 struct gpio_desc *devm_gpiod_get(struc 130 struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id,
137 enum 131 enum gpiod_flags flags)
138 132
139 struct gpio_desc *devm_gpiod_get_index 133 struct gpio_desc *devm_gpiod_get_index(struct device *dev,
140 134 const char *con_id,
141 135 unsigned int idx,
142 136 enum gpiod_flags flags)
143 137
144 struct gpio_desc *devm_gpiod_get_optio 138 struct gpio_desc *devm_gpiod_get_optional(struct device *dev,
145 139 const char *con_id,
146 140 enum gpiod_flags flags)
147 141
148 struct gpio_desc *devm_gpiod_get_index 142 struct gpio_desc *devm_gpiod_get_index_optional(struct device *dev,
149 143 const char *con_id,
150 144 unsigned int index,
151 145 enum gpiod_flags flags)
152 146
153 struct gpio_descs *devm_gpiod_get_arra 147 struct gpio_descs *devm_gpiod_get_array(struct device *dev,
154 148 const char *con_id,
155 149 enum gpiod_flags flags)
156 150
157 struct gpio_descs *devm_gpiod_get_arra 151 struct gpio_descs *devm_gpiod_get_array_optional(struct device *dev,
158 152 const char *con_id,
159 153 enum gpiod_flags flags)
160 154
161 A GPIO descriptor can be disposed of using the 155 A GPIO descriptor can be disposed of using the gpiod_put() function::
162 156
163 void gpiod_put(struct gpio_desc *desc) 157 void gpiod_put(struct gpio_desc *desc)
164 158
165 For an array of GPIOs this function can be use 159 For an array of GPIOs this function can be used::
166 160
167 void gpiod_put_array(struct gpio_descs 161 void gpiod_put_array(struct gpio_descs *descs)
168 162
169 It is strictly forbidden to use a descriptor a 163 It is strictly forbidden to use a descriptor after calling these functions.
170 It is also not allowed to individually release 164 It is also not allowed to individually release descriptors (using gpiod_put())
171 from an array acquired with gpiod_get_array(). 165 from an array acquired with gpiod_get_array().
172 166
173 The device-managed variants are, unsurprisingl 167 The device-managed variants are, unsurprisingly::
174 168
175 void devm_gpiod_put(struct device *dev 169 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
176 170
177 void devm_gpiod_put_array(struct devic 171 void devm_gpiod_put_array(struct device *dev, struct gpio_descs *descs)
178 172
179 173
180 Using GPIOs 174 Using GPIOs
181 =========== 175 ===========
182 176
183 Setting Direction 177 Setting Direction
184 ----------------- 178 -----------------
185 The first thing a driver must do with a GPIO i 179 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 180 direction-setting flags have been given to gpiod_get*(), this is done by
187 invoking one of the gpiod_direction_*() functi 181 invoking one of the gpiod_direction_*() functions::
188 182
189 int gpiod_direction_input(struct gpio_ 183 int gpiod_direction_input(struct gpio_desc *desc)
190 int gpiod_direction_output(struct gpio 184 int gpiod_direction_output(struct gpio_desc *desc, int value)
191 185
192 The return value is zero for success, else a n 186 The return value is zero for success, else a negative errno. It should be
193 checked, since the get/set calls don't return 187 checked, since the get/set calls don't return errors and since misconfiguration
194 is possible. You should normally issue these c 188 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 189 for spinlock-safe GPIOs it is OK to use them before tasking is enabled, as part
196 of early board setup. 190 of early board setup.
197 191
198 For output GPIOs, the value provided becomes t 192 For output GPIOs, the value provided becomes the initial output value. This
199 helps avoid signal glitching during system sta 193 helps avoid signal glitching during system startup.
200 194
201 A driver can also query the current direction 195 A driver can also query the current direction of a GPIO::
202 196
203 int gpiod_get_direction(const struct g 197 int gpiod_get_direction(const struct gpio_desc *desc)
204 198
205 This function returns 0 for output, 1 for inpu 199 This function returns 0 for output, 1 for input, or an error code in case of error.
206 200
207 Be aware that there is no default direction fo 201 Be aware that there is no default direction for GPIOs. Therefore, **using a GPIO
208 without setting its direction first is illegal 202 without setting its direction first is illegal and will result in undefined
209 behavior!** 203 behavior!**
210 204
211 205
212 Spinlock-Safe GPIO Access 206 Spinlock-Safe GPIO Access
213 ------------------------- 207 -------------------------
214 Most GPIO controllers can be accessed with mem 208 Most GPIO controllers can be accessed with memory read/write instructions. Those
215 don't need to sleep, and can safely be done fr 209 don't need to sleep, and can safely be done from inside hard (non-threaded) IRQ
216 handlers and similar contexts. 210 handlers and similar contexts.
217 211
218 Use the following calls to access GPIOs from a 212 Use the following calls to access GPIOs from an atomic context::
219 213
220 int gpiod_get_value(const struct gpio_ 214 int gpiod_get_value(const struct gpio_desc *desc);
221 void gpiod_set_value(struct gpio_desc 215 void gpiod_set_value(struct gpio_desc *desc, int value);
222 216
223 The values are boolean, zero for inactive, non !! 217 The values are boolean, zero for low, nonzero for high. When reading the value
224 value of an output pin, the value returned sho !! 218 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 !! 219 won't always match the specified output value, because of issues including
226 open-drain signaling and output latencies. 220 open-drain signaling and output latencies.
227 221
228 The get/set calls do not return errors because 222 The get/set calls do not return errors because "invalid GPIO" should have been
229 reported earlier from gpiod_direction_*(). How 223 reported earlier from gpiod_direction_*(). However, note that not all platforms
230 can read the value of output pins; those that 224 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 225 Also, using these calls for GPIOs that can't safely be accessed without sleeping
232 (see below) is an error. 226 (see below) is an error.
233 227
234 228
235 GPIO Access That May Sleep 229 GPIO Access That May Sleep
236 -------------------------- 230 --------------------------
237 Some GPIO controllers must be accessed using m 231 Some GPIO controllers must be accessed using message based buses like I2C or
238 SPI. Commands to read or write those GPIO valu 232 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 233 head of a queue to transmit a command and get its response. This requires
240 sleeping, which can't be done from inside IRQ 234 sleeping, which can't be done from inside IRQ handlers.
241 235
242 Platforms that support this type of GPIO disti 236 Platforms that support this type of GPIO distinguish them from other GPIOs by
243 returning nonzero from this call:: 237 returning nonzero from this call::
244 238
245 int gpiod_cansleep(const struct gpio_d 239 int gpiod_cansleep(const struct gpio_desc *desc)
246 240
247 To access such GPIOs, a different set of acces 241 To access such GPIOs, a different set of accessors is defined::
248 242
249 int gpiod_get_value_cansleep(const str 243 int gpiod_get_value_cansleep(const struct gpio_desc *desc)
250 void gpiod_set_value_cansleep(struct g 244 void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
251 245
252 Accessing such GPIOs requires a context which 246 Accessing such GPIOs requires a context which may sleep, for example a threaded
253 IRQ handler, and those accessors must be used 247 IRQ handler, and those accessors must be used instead of spinlock-safe
254 accessors without the cansleep() name suffix. 248 accessors without the cansleep() name suffix.
255 249
256 Other than the fact that these accessors might 250 Other than the fact that these accessors might sleep, and will work on GPIOs
257 that can't be accessed from hardIRQ handlers, 251 that can't be accessed from hardIRQ handlers, these calls act the same as the
258 spinlock-safe calls. 252 spinlock-safe calls.
259 253
260 254
261 .. _active_low_semantics: <<
262 <<
263 The active low and open drain semantics 255 The active low and open drain semantics
264 --------------------------------------- 256 ---------------------------------------
265 As a consumer should not have to care about th 257 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 258 gpiod_set_value_xxx() or gpiod_set_array_value_xxx() functions operate with
267 the *logical* value. With this they take the a 259 the *logical* value. With this they take the active low property into account.
268 This means that they check whether the GPIO is 260 This means that they check whether the GPIO is configured to be active low,
269 and if so, they manipulate the passed value be 261 and if so, they manipulate the passed value before the physical line level is
270 driven. 262 driven.
271 263
272 The same is applicable for open drain or open 264 The same is applicable for open drain or open source output lines: those do not
273 actively drive their output high (open drain) 265 actively drive their output high (open drain) or low (open source), they just
274 switch their output to a high impedance value. 266 switch their output to a high impedance value. The consumer should not need to
275 care. (For details read about open drain in dr !! 267 care. (For details read about open drain in driver.txt.)
276 268
277 With this, all the gpiod_set_(array)_value_xxx 269 With this, all the gpiod_set_(array)_value_xxx() functions interpret the
278 parameter "value" as "active" ("1") or "inacti !! 270 parameter "value" as "asserted" ("1") or "de-asserted" ("0"). The physical line
279 level will be driven accordingly. 271 level will be driven accordingly.
280 272
281 As an example, if the active low property for 273 As an example, if the active low property for a dedicated GPIO is set, and the
282 gpiod_set_(array)_value_xxx() passes "active" !! 274 gpiod_set_(array)_value_xxx() passes "asserted" ("1"), the physical line level
283 will be driven low. 275 will be driven low.
284 276
285 To summarize:: 277 To summarize::
286 278
287 Function (example) line prop 279 Function (example) line property physical line
288 gpiod_set_raw_value(desc, 0); don't car 280 gpiod_set_raw_value(desc, 0); don't care low
289 gpiod_set_raw_value(desc, 1); don't car 281 gpiod_set_raw_value(desc, 1); don't care high
290 gpiod_set_value(desc, 0); default ( 282 gpiod_set_value(desc, 0); default (active high) low
291 gpiod_set_value(desc, 1); default ( 283 gpiod_set_value(desc, 1); default (active high) high
292 gpiod_set_value(desc, 0); active lo 284 gpiod_set_value(desc, 0); active low high
293 gpiod_set_value(desc, 1); active lo 285 gpiod_set_value(desc, 1); active low low
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 struct gpio_array *array_info,
337 unsigned lon 327 unsigned long *value_bitmap);
338 int gpiod_get_raw_array_value(unsigned 328 int gpiod_get_raw_array_value(unsigned int array_size,
339 struct g 329 struct gpio_desc **desc_array,
340 struct g 330 struct gpio_array *array_info,
341 unsigned 331 unsigned long *value_bitmap);
342 int gpiod_get_array_value_cansleep(uns 332 int gpiod_get_array_value_cansleep(unsigned int array_size,
343 str 333 struct gpio_desc **desc_array,
344 str 334 struct gpio_array *array_info,
345 uns 335 unsigned long *value_bitmap);
346 int gpiod_get_raw_array_value_cansleep 336 int gpiod_get_raw_array_value_cansleep(unsigned int array_size,
347 str 337 struct gpio_desc **desc_array,
348 str 338 struct gpio_array *array_info,
349 uns 339 unsigned long *value_bitmap);
350 340
351 int gpiod_set_array_value(unsigned int 341 int gpiod_set_array_value(unsigned int array_size,
352 struct gpio_ 342 struct gpio_desc **desc_array,
353 struct gpio_ 343 struct gpio_array *array_info,
354 unsigned lon 344 unsigned long *value_bitmap)
355 int gpiod_set_raw_array_value(unsigned 345 int gpiod_set_raw_array_value(unsigned int array_size,
356 struct g 346 struct gpio_desc **desc_array,
357 struct g 347 struct gpio_array *array_info,
358 unsigned 348 unsigned long *value_bitmap)
359 int gpiod_set_array_value_cansleep(uns 349 int gpiod_set_array_value_cansleep(unsigned int array_size,
360 str 350 struct gpio_desc **desc_array,
361 str 351 struct gpio_array *array_info,
362 uns 352 unsigned long *value_bitmap)
363 int gpiod_set_raw_array_value_cansleep 353 int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
364 354 struct gpio_desc **desc_array,
365 355 struct gpio_array *array_info,
366 356 unsigned long *value_bitmap)
367 357
368 The array can be an arbitrary set of GPIOs. Th 358 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 359 GPIOs belonging to the same bank or chip simultaneously if supported by the
370 corresponding chip driver. In that case a sign 360 corresponding chip driver. In that case a significantly improved performance
371 can be expected. If simultaneous access is not 361 can be expected. If simultaneous access is not possible the GPIOs will be
372 accessed sequentially. 362 accessed sequentially.
373 363
374 The functions take four arguments: 364 The functions take four arguments:
375 365
376 * array_size - the number of array 366 * array_size - the number of array elements
377 * desc_array - an array of GPIO des 367 * desc_array - an array of GPIO descriptors
378 * array_info - optional information 368 * array_info - optional information obtained from gpiod_get_array()
379 * value_bitmap - a bitmap to store th 369 * value_bitmap - a bitmap to store the GPIOs' values (get) or
380 a bitmap of values to assign to the 370 a bitmap of values to assign to the GPIOs (set)
381 371
382 The descriptor array can be obtained using the 372 The descriptor array can be obtained using the gpiod_get_array() function
383 or one of its variants. If the group of descri 373 or one of its variants. If the group of descriptors returned by that function
384 matches the desired group of GPIOs, those GPIO 374 matches the desired group of GPIOs, those GPIOs can be accessed by simply using
385 the struct gpio_descs returned by gpiod_get_ar 375 the struct gpio_descs returned by gpiod_get_array()::
386 376
387 struct gpio_descs *my_gpio_descs = gpi 377 struct gpio_descs *my_gpio_descs = gpiod_get_array(...);
388 gpiod_set_array_value(my_gpio_descs->n 378 gpiod_set_array_value(my_gpio_descs->ndescs, my_gpio_descs->desc,
389 my_gpio_descs->i 379 my_gpio_descs->info, my_gpio_value_bitmap);
390 380
391 It is also possible to access a completely arb 381 It is also possible to access a completely arbitrary array of descriptors. The
392 descriptors may be obtained using any combinat 382 descriptors may be obtained using any combination of gpiod_get() and
393 gpiod_get_array(). Afterwards the array of des 383 gpiod_get_array(). Afterwards the array of descriptors has to be setup
394 manually before it can be passed to one of the 384 manually before it can be passed to one of the above functions. In that case,
395 array_info should be set to NULL. 385 array_info should be set to NULL.
396 386
397 Note that for optimal performance GPIOs belong 387 Note that for optimal performance GPIOs belonging to the same chip should be
398 contiguous within the array of descriptors. 388 contiguous within the array of descriptors.
399 389
400 Still better performance may be achieved if ar 390 Still better performance may be achieved if array indexes of the descriptors
401 match hardware pin numbers of a single chip. 391 match hardware pin numbers of a single chip. If an array passed to a get/set
402 array function matches the one obtained from g 392 array function matches the one obtained from gpiod_get_array() and array_info
403 associated with the array is also passed, the 393 associated with the array is also passed, the function may take a fast bitmap
404 processing path, passing the value_bitmap argu 394 processing path, passing the value_bitmap argument directly to the respective
405 .get/set_multiple() callback of the chip. Tha 395 .get/set_multiple() callback of the chip. That allows for utilization of GPIO
406 banks as data I/O ports without much loss of p 396 banks as data I/O ports without much loss of performance.
407 397
408 The return value of gpiod_get_array_value() an 398 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 399 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 400 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 401 values are stored in value_array rather than passed back as return value.
412 402
413 403
414 GPIOs mapped to IRQs 404 GPIOs mapped to IRQs
415 -------------------- 405 --------------------
416 GPIO lines can quite often be used as IRQs. Yo 406 GPIO lines can quite often be used as IRQs. You can get the IRQ number
417 corresponding to a given GPIO using the follow 407 corresponding to a given GPIO using the following call::
418 408
419 int gpiod_to_irq(const struct gpio_des 409 int gpiod_to_irq(const struct gpio_desc *desc)
420 410
421 It will return an IRQ number, or a negative er 411 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 412 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 413 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 414 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 415 from gpiod_to_irq(). gpiod_to_irq() is not allowed to sleep.
426 416
427 Non-error values returned from gpiod_to_irq() 417 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 418 free_irq(). They will often be stored into IRQ resources for platform devices,
429 by the board-specific initialization code. Not 419 by the board-specific initialization code. Note that IRQ trigger options are
430 part of the IRQ interface, e.g. IRQF_TRIGGER_F 420 part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are system wakeup
431 capabilities. 421 capabilities.
432 422
433 423
434 GPIOs and ACPI 424 GPIOs and ACPI
435 ============== 425 ==============
436 426
437 On ACPI systems, GPIOs are described by GpioIo 427 On ACPI systems, GPIOs are described by GpioIo()/GpioInt() resources listed by
438 the _CRS configuration objects of devices. Th 428 the _CRS configuration objects of devices. Those resources do not provide
439 connection IDs (names) for GPIOs, so it is nec 429 connection IDs (names) for GPIOs, so it is necessary to use an additional
440 mechanism for this purpose. 430 mechanism for this purpose.
441 431
442 Systems compliant with ACPI 5.1 or newer may p 432 Systems compliant with ACPI 5.1 or newer may provide a _DSD configuration object
443 which, among other things, may be used to prov 433 which, among other things, may be used to provide connection IDs for specific
444 GPIOs described by the GpioIo()/GpioInt() reso 434 GPIOs described by the GpioIo()/GpioInt() resources in _CRS. If that is the
445 case, it will be handled by the GPIO subsystem 435 case, it will be handled by the GPIO subsystem automatically. However, if the
446 _DSD is not present, the mappings between Gpio 436 _DSD is not present, the mappings between GpioIo()/GpioInt() resources and GPIO
447 connection IDs need to be provided by device d 437 connection IDs need to be provided by device drivers.
448 438
449 For details refer to Documentation/firmware-gu 439 For details refer to Documentation/firmware-guide/acpi/gpio-properties.rst
450 440
451 441
452 Interacting With the Legacy GPIO Subsystem 442 Interacting With the Legacy GPIO Subsystem
453 ========================================== 443 ==========================================
454 Many kernel subsystems and drivers still handl 444 Many kernel subsystems and drivers still handle GPIOs using the legacy
455 integer-based interface. It is strongly recomm 445 integer-based interface. It is strongly recommended to update these to the new
456 gpiod interface. For cases where both interfac 446 gpiod interface. For cases where both interfaces need to be used, the following
457 two functions allow to convert a GPIO descript 447 two functions allow to convert a GPIO descriptor into the GPIO integer namespace
458 and vice-versa:: 448 and vice-versa::
459 449
460 int desc_to_gpio(const struct gpio_des 450 int desc_to_gpio(const struct gpio_desc *desc)
461 struct gpio_desc *gpio_to_desc(unsigne 451 struct gpio_desc *gpio_to_desc(unsigned gpio)
462 452
463 The GPIO number returned by desc_to_gpio() can 453 The GPIO number returned by desc_to_gpio() can safely be used as a parameter of
464 the gpio\_*() functions for as long as the GPI 454 the gpio\_*() functions for as long as the GPIO descriptor `desc` is not freed.
465 All the same, a GPIO number passed to gpio_to_ 455 All the same, a GPIO number passed to gpio_to_desc() must first be properly
466 acquired using e.g. gpio_request_one(), and th 456 acquired using e.g. gpio_request_one(), and the returned GPIO descriptor is only
467 considered valid until that GPIO number is rel 457 considered valid until that GPIO number is released using gpio_free().
468 458
469 Freeing a GPIO obtained by one API with the ot 459 Freeing a GPIO obtained by one API with the other API is forbidden and an
470 unchecked error. 460 unchecked error.
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