counter: Introduce the COUNTER_COMP_ARRAY component type

The COUNTER_COMP_ARRAY Counter component type is introduced to enable
support for Counter array components. With Counter array components,
exposure for buffers on counter devices can be defined via new Counter
array component macros. This should simplify code for driver authors who
would otherwise need to define individual Counter components for each
array element.

Eight Counter array component macros are introduced::

        DEFINE_COUNTER_ARRAY_U64(_name, _length)
        DEFINE_COUNTER_ARRAY_CAPTURE(_name, _length)
        DEFINE_COUNTER_ARRAY_POLARITY(_name, _enums, _length)
        COUNTER_COMP_DEVICE_ARRAY_U64(_name, _read, _write, _array)
        COUNTER_COMP_COUNT_ARRAY_U64(_name, _read, _write, _array)
        COUNTER_COMP_SIGNAL_ARRAY_U64(_name, _read, _write, _array)
        COUNTER_COMP_ARRAY_CAPTURE(_read, _write, _array)
        COUNTER_COMP_ARRAY_POLARITY(_read, _write, _array)

Eight Counter array callbacks are introduced as well::

        int (*signal_array_u32_read)(struct counter_device *counter,
                                     struct counter_signal *signal,
                                     size_t idx, u32 *val);
        int (*signal_array_u32_write)(struct counter_device *counter,
                                      struct counter_signal *signal,
                                      size_t idx, u32 val);
        int (*device_array_u64_read)(struct counter_device *counter,
                                     size_t idx, u64 *val);
        int (*count_array_u64_read)(struct counter_device *counter,
                                    struct counter_count *count,
                                    size_t idx, u64 *val);
        int (*signal_array_u64_read)(struct counter_device *counter,
                                     struct counter_signal *signal,
                                     size_t idx, u64 *val);
        int (*device_array_u64_write)(struct counter_device *counter,
                                      size_t idx, u64 val);
        int (*count_array_u64_write)(struct counter_device *counter,
                                     struct counter_count *count,
                                     size_t idx, u64 val);
        int (*signal_array_u64_write)(struct counter_device *counter,
                                      struct counter_signal *signal,
                                      size_t idx, u64 val);

Driver authors can handle reads/writes for an array component by
receiving an element index via the `idx` parameter and processing the
respective value via the `val` parameter.

For example, suppose a driver wants to expose a Count's read-only
capture buffer of four elements using a callback
`foobar_capture_read()`::

        DEFINE_COUNTER_ARRAY_CAPTURE(foobar_capture_array, 4);
        COUNTER_COMP_ARRAY_CAPTURE(foobar_capture_read, NULL,
                                   foobar_capture_array)

Respective sysfs attributes for each array element would appear for the
respective Count:

* /sys/bus/counter/devices/counterX/countY/capture0
* /sys/bus/counter/devices/counterX/countY/capture1
* /sys/bus/counter/devices/counterX/countY/capture2
* /sys/bus/counter/devices/counterX/countY/capture3

If a user tries to read _capture2_ for example, `idx` will be `2` when
passed to the `foobar_capture_read()` callback, and thus the driver
knows which array element to handle.

Counter arrays for polarity elements can be defined in a similar
manner as u64 elements::

        const enum counter_signal_polarity foobar_polarity_states[] = {
                COUNTER_SIGNAL_POLARITY_POSITIVE,
                COUNTER_SIGNAL_POLARITY_NEGATIVE,
        };
        DEFINE_COUNTER_ARRAY_POLARITY(foobar_polarity_array,
                                      foobar_polarity_states, 4);
        COUNTER_COMP_ARRAY_POLARITY(foobar_polarity_read,
                                    foobar_polarity_write,
                                    foobar_polarity_array)

Tested-by: Julien Panis <[email protected]>
Link: https://lore.kernel.org/r/5310c22520aeae65b1b74952419f49ac4c8e1ec1.1664204990.git.william.gray@linaro.org/
Signed-off-by: William Breathitt Gray <[email protected]>
Link: https://lore.kernel.org/r/a51fd608704bdfc5a0efa503fc5481df34241e0a.1664318353.git.william.gray@linaro.org
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: William Breathitt Gray

drivers/counter/counter-chrdev.c

@@ -40,7 +40,11 @@ struct counter_comp_node {
 	a.signal_u32_read == b.signal_u32_read || \
 	a.device_u64_read == b.device_u64_read || \
 	a.count_u64_read == b.count_u64_read || \
-	a.signal_u64_read == b.signal_u64_read)
+	a.signal_u64_read == b.signal_u64_read || \
+	a.signal_array_u32_read == b.signal_array_u32_read || \
+	a.device_array_u64_read == b.device_array_u64_read || \
+	a.count_array_u64_read == b.count_array_u64_read || \
+	a.signal_array_u64_read == b.signal_array_u64_read)
 
 #define counter_comp_read_is_set(comp) \
 	(comp.action_read || \
@@ -52,7 +56,11 @@ struct counter_comp_node {
 	comp.signal_u32_read || \
 	comp.device_u64_read || \
 	comp.count_u64_read || \
-	comp.signal_u64_read)
+	comp.signal_u64_read || \
+	comp.signal_array_u32_read || \
+	comp.device_array_u64_read || \
+	comp.count_array_u64_read || \
+	comp.signal_array_u64_read)
 
 static ssize_t counter_chrdev_read(struct file *filp, char __user *buf,
 				   size_t len, loff_t *f_ps)
@@ -228,6 +236,31 @@ static int counter_disable_events(struct counter_device *const counter)
 	return err;
 }
 
+static int counter_get_ext(const struct counter_comp *const ext,
+			   const size_t num_ext, const size_t component_id,
+			   size_t *const ext_idx, size_t *const id)
+{
+	struct counter_array *element;
+
+	*id = 0;
+	for (*ext_idx = 0; *ext_idx < num_ext; (*ext_idx)++) {
+		if (*id == component_id)
+			return 0;
+
+		if (ext->type == COUNTER_COMP_ARRAY) {
+			element = ext->priv;
+
+			if (component_id - *id < element->length)
+				return 0;
+
+			*id += element->length;
+		} else
+			(*id)++;
+	}
+
+	return -EINVAL;
+}
+
 static int counter_add_watch(struct counter_device *const counter,
 			     const unsigned long arg)
 {
@@ -237,6 +270,7 @@ static int counter_add_watch(struct counter_device *const counter,
 	size_t parent, id;
 	struct counter_comp *ext;
 	size_t num_ext;
+	size_t ext_idx, ext_id;
 	int err = 0;
 
 	if (copy_from_user(&watch, uwatch, sizeof(watch)))
@@ -314,11 +348,11 @@ static int counter_add_watch(struct counter_device *const counter,
 		comp_node.comp.priv = counter->counts[parent].synapses + id;
 		break;
 	case COUNTER_COMPONENT_EXTENSION:
-		if (id >= num_ext)
-			return -EINVAL;
-		id = array_index_nospec(id, num_ext);
+		err = counter_get_ext(ext, num_ext, id, &ext_idx, &ext_id);
+		if (err < 0)
+			return err;
 
-		comp_node.comp = ext[id];
+		comp_node.comp = ext[ext_idx];
 		break;
 	default:
 		return -EINVAL;
@@ -451,14 +485,56 @@ void counter_chrdev_remove(struct counter_device *const counter)
 	kfifo_free(&counter->events);
 }
 
+static int counter_get_array_data(struct counter_device *const counter,
+				  const enum counter_scope scope,
+				  void *const parent,
+				  const struct counter_comp *const comp,
+				  const size_t idx, u64 *const value)
+{
+	const struct counter_array *const element = comp->priv;
+	u32 value_u32 = 0;
+	int ret;
+
+	switch (element->type) {
+	case COUNTER_COMP_SIGNAL_POLARITY:
+		if (scope != COUNTER_SCOPE_SIGNAL)
+			return -EINVAL;
+		ret = comp->signal_array_u32_read(counter, parent, idx,
+						  &value_u32);
+		*value = value_u32;
+		return ret;
+	case COUNTER_COMP_U64:
+		switch (scope) {
+		case COUNTER_SCOPE_DEVICE:
+			return comp->device_array_u64_read(counter, idx, value);
+		case COUNTER_SCOPE_SIGNAL:
+			return comp->signal_array_u64_read(counter, parent, idx,
+							   value);
+		case COUNTER_SCOPE_COUNT:
+			return comp->count_array_u64_read(counter, parent, idx,
+							  value);
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
 static int counter_get_data(struct counter_device *const counter,
 			    const struct counter_comp_node *const comp_node,
 			    u64 *const value)
 {
 	const struct counter_comp *const comp = &comp_node->comp;
-	void *const parent = comp_node->parent;
+	const enum counter_scope scope = comp_node->component.scope;
+	const size_t id = comp_node->component.id;
+	struct counter_signal *const signal = comp_node->parent;
+	struct counter_count *const count = comp_node->parent;
 	u8 value_u8 = 0;
 	u32 value_u32 = 0;
+	const struct counter_comp *ext;
+	size_t num_ext;
+	size_t ext_idx, ext_id;
 	int ret;
 
 	if (comp_node->component.type == COUNTER_COMPONENT_NONE)
@@ -467,15 +543,15 @@ static int counter_get_data(struct counter_device *const counter,
 	switch (comp->type) {
 	case COUNTER_COMP_U8:
 	case COUNTER_COMP_BOOL:
-		switch (comp_node->component.scope) {
+		switch (scope) {
 		case COUNTER_SCOPE_DEVICE:
 			ret = comp->device_u8_read(counter, &value_u8);
 			break;
 		case COUNTER_SCOPE_SIGNAL:
-			ret = comp->signal_u8_read(counter, parent, &value_u8);
+			ret = comp->signal_u8_read(counter, signal, &value_u8);
 			break;
 		case COUNTER_SCOPE_COUNT:
-			ret = comp->count_u8_read(counter, parent, &value_u8);
+			ret = comp->count_u8_read(counter, count, &value_u8);
 			break;
 		default:
 			return -EINVAL;
@@ -488,38 +564,60 @@ static int counter_get_data(struct counter_device *const counter,
 	case COUNTER_COMP_COUNT_DIRECTION:
 	case COUNTER_COMP_COUNT_MODE:
 	case COUNTER_COMP_SIGNAL_POLARITY:
-		switch (comp_node->component.scope) {
+		switch (scope) {
 		case COUNTER_SCOPE_DEVICE:
 			ret = comp->device_u32_read(counter, &value_u32);
 			break;
 		case COUNTER_SCOPE_SIGNAL:
-			ret = comp->signal_u32_read(counter, parent,
+			ret = comp->signal_u32_read(counter, signal,
 						    &value_u32);
 			break;
 		case COUNTER_SCOPE_COUNT:
-			ret = comp->count_u32_read(counter, parent, &value_u32);
+			ret = comp->count_u32_read(counter, count, &value_u32);
 			break;
 		default:
 			return -EINVAL;
 		}
 		*value = value_u32;
 		return ret;
 	case COUNTER_COMP_U64:
-		switch (comp_node->component.scope) {
+		switch (scope) {
 		case COUNTER_SCOPE_DEVICE:
 			return comp->device_u64_read(counter, value);
 		case COUNTER_SCOPE_SIGNAL:
-			return comp->signal_u64_read(counter, parent, value);
+			return comp->signal_u64_read(counter, signal, value);
 		case COUNTER_SCOPE_COUNT:
-			return comp->count_u64_read(counter, parent, value);
+			return comp->count_u64_read(counter, count, value);
 		default:
 			return -EINVAL;
 		}
 	case COUNTER_COMP_SYNAPSE_ACTION:
-		ret = comp->action_read(counter, parent, comp->priv,
-					&value_u32);
+		ret = comp->action_read(counter, count, comp->priv, &value_u32);
 		*value = value_u32;
 		return ret;
+	case COUNTER_COMP_ARRAY:
+		switch (scope) {
+		case COUNTER_SCOPE_DEVICE:
+			ext = counter->ext;
+			num_ext = counter->num_ext;
+			break;
+		case COUNTER_SCOPE_SIGNAL:
+			ext = signal->ext;
+			num_ext = signal->num_ext;
+			break;
+		case COUNTER_SCOPE_COUNT:
+			ext = count->ext;
+			num_ext = count->num_ext;
+			break;
+		default:
+			return -EINVAL;
+		}
+		ret = counter_get_ext(ext, num_ext, id, &ext_idx, &ext_id);
+		if (ret < 0)
+			return ret;
+
+		return counter_get_array_data(counter, scope, comp_node->parent,
+					      comp, id - ext_id, value);
 	default:
 		return -EINVAL;
 	}