processing. If yes, a bitmap is passed over get/set array functions directly
between a caller and a respective .get/set_multiple() callback of a GPIO chip.
-In order to qualify for fast bitmap processing, the pin mapping must meet the
+In order to qualify for fast bitmap processing, the array must meet the
following requirements:
-- it must belong to the same chip as other 'fast' pins of the function,
-- its index within the function must match its hardware number within the chip.
-
-Open drain and open source pins are excluded from fast bitmap output processing.
+- pin hardware number of array member 0 must also be 0,
+- pin hardware numbers of consecutive array members which belong to the same
+ chip as member 0 does must also match their array indexes.
+
+Otherwise fast bitmap processing path is not used in order to avoid consecutive
+pins which belong to the same chip but are not in hardware order being processed
+separately.
+
+If the array applies for fast bitmap processing path, pins which belong to
+different chips than member 0 does, as well as those with indexes different from
+their hardware pin numbers, are excluded from the fast path, both input and
+output. Moreover, open drain and open source pins are excluded from fast bitmap
+output processing.
chip = gpiod_to_chip(desc);
/*
- * Select a chip of first array member
- * whose index matches its pin hardware number
- * as a candidate for fast bitmap processing.
+ * If pin hardware number of array member 0 is also 0, select
+ * its chip as a candidate for fast bitmap processing path.
*/
- if (!array_info && gpio_chip_hwgpio(desc) == descs->ndescs) {
+ if (descs->ndescs == 0 && gpio_chip_hwgpio(desc) == 0) {
struct gpio_descs *array;
bitmap_size = BITS_TO_LONGS(chip->ngpio > count ?
count - descs->ndescs);
descs->info = array_info;
}
- /*
- * Unmark members which don't qualify for fast bitmap
- * processing (different chip, not in hardware order)
- */
- if (array_info && (chip != array_info->chip ||
- gpio_chip_hwgpio(desc) != descs->ndescs)) {
+ /* Unmark array members which don't belong to the 'fast' chip */
+ if (array_info && array_info->chip != chip) {
__clear_bit(descs->ndescs, array_info->get_mask);
__clear_bit(descs->ndescs, array_info->set_mask);
+ }
+ /*
+ * Detect array members which belong to the 'fast' chip
+ * but their pins are not in hardware order.
+ */
+ else if (array_info &&
+ gpio_chip_hwgpio(desc) != descs->ndescs) {
+ /*
+ * Don't use fast path if all array members processed so
+ * far belong to the same chip as this one but its pin
+ * hardware number is different from its array index.
+ */
+ if (bitmap_full(array_info->get_mask, descs->ndescs)) {
+ array_info = NULL;
+ } else {
+ __clear_bit(descs->ndescs,
+ array_info->get_mask);
+ __clear_bit(descs->ndescs,
+ array_info->set_mask);
+ }
} else if (array_info) {
/* Exclude open drain or open source from fast output */
if (gpiochip_line_is_open_drain(chip, descs->ndescs) ||