[PATCH v2 01/15] nvmem: add support for cell lookups

Bartosz Golaszewski
2018-06-26T10:30:42Z

We can currently only register nvmem cells from device tree or by
manually calling nvmem_add_cells(). The latter options however forces
users to make sure that the nvmem provider with which the cells are
associated is registered before the call.

This patch proposes a new solution inspired by other frameworks that
offer resource lookups (GPIO, PWM etc.). It adds a function that allows
machine code to register nvmem lookup which are later lazily used to
add corresponding nvmem cells.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/nvmem/core.c | 57 +++++++++++++++++++++++++++++++++-
include/linux/nvmem-consumer.h | 6 ++++
include/linux/nvmem-provider.h | 6 ++++
3 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index b5b0cdc21d01..a2e87b464319 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -62,6 +62,9 @@ static DEFINE_IDA(nvmem_ida);
static LIST_HEAD(nvmem_cells);
static DEFINE_MUTEX(nvmem_cells_mutex);

+static LIST_HEAD(nvmem_cell_lookups);
+static DEFINE_MUTEX(nvmem_lookup_mutex);
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key eeprom_lock_key;
#endif
@@ -247,6 +250,23 @@ static const struct attribute_group *nvmem_ro_root_dev_groups[] = {
NULL,
};

+/**
+ * nvmem_register_lookup() - register a number of nvmem cell lookup entries
+ *
+ * @lookup: array of nvmem cell lookup entries
+ * @nentries: number of lookup entries in the array
+ */
+void nvmem_register_lookup(struct nvmem_cell_lookup *lookup, size_t nentries)
+{
+ int i;
+
+ mutex_lock(&nvmem_lookup_mutex);
+ for (i = 0; i < nentries; i++)
+ list_add_tail(&lookup[i].list, &nvmem_cell_lookups);
+ mutex_unlock(&nvmem_lookup_mutex);
+}
+EXPORT_SYMBOL_GPL(nvmem_register_lookup);
+
static void nvmem_release(struct device *dev)
{
struct nvmem_device *nvmem = to_nvmem_device(dev);
@@ -916,6 +936,37 @@ struct nvmem_cell *of_nvmem_cell_get(struct device_node *np,
EXPORT_SYMBOL_GPL(of_nvmem_cell_get);
#endif

+static struct nvmem_cell *nvmem_cell_from_lookup(const char *cell_id)
+{
+ struct nvmem_cell *cell = ERR_PTR(-EPROBE_DEFER);
+ struct nvmem_cell_lookup *lookup;
+ struct nvmem_device *nvmem;
+ int rc;
+
+ mutex_lock(&nvmem_lookup_mutex);
+
+ list_for_each_entry(lookup, &nvmem_cell_lookups, list) {
+ if (strcmp(cell_id, lookup->info.name) == 0) {
+ nvmem = nvmem_find(lookup->nvmem_name);
+ if (!nvmem)
+ goto out;
+
+ rc = nvmem_add_cells(nvmem, &lookup->info, 1);
+ if (rc) {
+ cell = ERR_PTR(rc);
+ goto out;
+ }
+
+ cell = nvmem_cell_get_from_list(cell_id);
+ break;
+ }
+ }
+
+out:
+ mutex_unlock(&nvmem_lookup_mutex);
+ return cell;
+}
+
/**
* nvmem_cell_get() - Get nvmem cell of device form a given cell name
*
@@ -936,7 +987,11 @@ struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *cell_id)
return cell;
}

- return nvmem_cell_get_from_list(cell_id);
+ cell = nvmem_cell_get_from_list(cell_id);
+ if (!IS_ERR(cell) || PTR_ERR(cell) == -EPROBE_DEFER)
+ return cell;
+
+ return nvmem_cell_from_lookup(cell_id);
}
EXPORT_SYMBOL_GPL(nvmem_cell_get);

diff --git a/include/linux/nvmem-consumer.h b/include/linux/nvmem-consumer.h
index 4e85447f7860..f4b5d3186e94 100644
--- a/include/linux/nvmem-consumer.h
+++ b/include/linux/nvmem-consumer.h
@@ -29,6 +29,12 @@ struct nvmem_cell_info {
unsigned int nbits;
};

+struct nvmem_cell_lookup {
+ struct nvmem_cell_info info;
+ struct list_head list;
+ const char *nvmem_name;
+};
+
#if IS_ENABLED(CONFIG_NVMEM)

/* Cell based interface */
diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
index 24def6ad09bb..766c0a96c113 100644
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -17,6 +17,7 @@

struct nvmem_device;
struct nvmem_cell_info;
+struct nvmem_cell_lookup;
typedef int (*nvmem_reg_read_t)(void *priv, unsigned int offset,
void *val, size_t bytes);
typedef int (*nvmem_reg_write_t)(void *priv, unsigned int offset,
@@ -72,6 +73,8 @@ struct nvmem_config {
struct nvmem_device *nvmem_register(const struct nvmem_config *cfg);
int nvmem_unregister(struct nvmem_device *nvmem);

+void nvmem_register_lookup(struct nvmem_cell_lookup *lookup, size_t nentries);
+
struct nvmem_device *devm_nvmem_register(struct device *dev,
const struct nvmem_config *cfg);

@@ -92,6 +95,9 @@ static inline int nvmem_unregister(struct nvmem_device *nvmem)
return -ENOSYS;
}

+static inline void
+nvmem_register_lookup(struct nvmem_cell_lookup *lookup, size_t nentries) {}
+
static inline struct nvmem_device *
devm_nvmem_register(struct device *dev, const struct nvmem_config *c)
{
--
2.17.1