path: root/Documentation/driver-api
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authorJanusz Krzysztofik <jmkrzyszt@gmail.com>2018-09-05 23:50:06 +0200
committerLinus Walleij <linus.walleij@linaro.org>2018-09-13 11:16:12 +0200
commitbf9346f5d47b4506aafbc384dfb5796b0adc3f8d (patch)
tree36059c2536ba006875029d5edbe9615d98dc3180 /Documentation/driver-api
parentb9762bebc6332b40c33e03dea03e30fa12d9e3ed (diff)
gpiolib: Identify arrays matching GPIO hardware
Certain GPIO array lookup results may map directly to GPIO pins of a single GPIO chip in hardware order. If that condition is recognized and handled efficiently, significant performance gain of get/set array functions may be possible. While processing a request for an array of GPIO descriptors, identify those which represent corresponding pins of a single GPIO chip. Skip over pins which require open source or open drain special processing. Moreover, identify pins which require inversion. Pass a pointer to that information with the array to the caller so it can benefit from enhanced performance as soon as get/set array functions can accept and make efficient use of it. Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'Documentation/driver-api')
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/driver-api/gpio/consumer.rst b/Documentation/driver-api/gpio/consumer.rst
index ed68042ddccf..7e0298b9a7b9 100644
--- a/Documentation/driver-api/gpio/consumer.rst
+++ b/Documentation/driver-api/gpio/consumer.rst
@@ -109,9 +109,11 @@ For a function using multiple GPIOs all of those can be obtained with one call::
enum gpiod_flags flags)
This function returns a struct gpio_descs which contains an array of
+descriptors. It also contains a pointer to a gpiolib private structure which,
+if passed back to get/set array functions, may speed up I/O proocessing::
struct gpio_descs {
+ struct gpio_array *info;
unsigned int ndescs;
struct gpio_desc *desc[];