This function allows nvmem consumers to know the size of an nvmem cell
before calling nvmem_cell_write() or nvmem_cell_read(), which is helpful
for drivers that may need to handle devices with different cell sizes.

Signed-off-by: Jennifer Berringer <jberring@redhat.com>
---
 drivers/nvmem/core.c           | 18 ++++++++++++++++++
 include/linux/nvmem-consumer.h |  6 ++++++
 2 files changed, 24 insertions(+)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index d6494dfc20a7..4d0cbd20da48 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1624,6 +1624,24 @@ void nvmem_cell_put(struct nvmem_cell *cell)
 }
 EXPORT_SYMBOL_GPL(nvmem_cell_put);
 
+/**
+ * nvmem_cell_size() - Get nvmem cell size in bytes.
+ *
+ * @cell: nvmem cell.
+ *
+ * Return: size of the nvmem cell.
+ */
+size_t nvmem_cell_size(struct nvmem_cell *cell)
+{
+	struct nvmem_cell_entry *entry = cell->entry;
+
+	if (!entry)
+		return 0;
+
+	return entry->bytes;
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_size);
+
 static void nvmem_shift_read_buffer_in_place(struct nvmem_cell_entry *cell, void *buf)
 {
 	u8 *p, *b;
diff --git a/include/linux/nvmem-consumer.h b/include/linux/nvmem-consumer.h
index 34c0e58dfa26..a2020527d2d3 100644
--- a/include/linux/nvmem-consumer.h
+++ b/include/linux/nvmem-consumer.h
@@ -54,6 +54,7 @@ struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *id);
 struct nvmem_cell *devm_nvmem_cell_get(struct device *dev, const char *id);
 void nvmem_cell_put(struct nvmem_cell *cell);
 void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell);
+size_t nvmem_cell_size(struct nvmem_cell *cell);
 void *nvmem_cell_read(struct nvmem_cell *cell, size_t *len);
 int nvmem_cell_write(struct nvmem_cell *cell, void *buf, size_t len);
 int nvmem_cell_read_u8(struct device *dev, const char *cell_id, u8 *val);
@@ -117,6 +118,11 @@ static inline void nvmem_cell_put(struct nvmem_cell *cell)
 {
 }
 
+static inline size_t nvmem_cell_size(struct nvmem_cell *cell)
+{
+	return 0;
+}
+
 static inline void *nvmem_cell_read(struct nvmem_cell *cell, size_t *len)
 {
 	return ERR_PTR(-EOPNOTSUPP);
-- 
2.47.1

Hi Jennifer,

On 28/02/2025 18:03, Jennifer Berringer wrote:
> This function allows nvmem consumers to know the size of an nvmem cell
> before calling nvmem_cell_write() or nvmem_cell_read(), which is helpful
> for drivers that may need to handle devices with different cell sizes.
> 
> Signed-off-by: Jennifer Berringer <jberring@redhat.com>
> ---
>   drivers/nvmem/core.c           | 18 ++++++++++++++++++
>   include/linux/nvmem-consumer.h |  6 ++++++
>   2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index d6494dfc20a7..4d0cbd20da48 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -1624,6 +1624,24 @@ void nvmem_cell_put(struct nvmem_cell *cell)
>   }
>   EXPORT_SYMBOL_GPL(nvmem_cell_put);
>   
> +/**
> + * nvmem_cell_size() - Get nvmem cell size in bytes.
> + *
> + * @cell: nvmem cell.
> + *
> + * Return: size of the nvmem cell.
> + */
> +size_t nvmem_cell_size(struct nvmem_cell *cell)
> +{
> +	struct nvmem_cell_entry *entry = cell->entry;
> +
> +	if (!entry)
> +		return 0;
> +
> +	return entry->bytes;
> +}
> +EXPORT_SYMBOL_GPL(nvmem_cell_size);
> +

There is a similar patch on the list, could you take a look and see if 
that is usable in power reset driver.

https://lore.kernel.org/lkml/20250306093900.2199442-3-o.rempel@pengutronix.de/T/#m97bbb1870d7140661894a4e806a695e563588524



--srini
>   static void nvmem_shift_read_buffer_in_place(struct nvmem_cell_entry *cell, void *buf)
>   {
>   	u8 *p, *b;
> diff --git a/include/linux/nvmem-consumer.h b/include/linux/nvmem-consumer.h
> index 34c0e58dfa26..a2020527d2d3 100644
> --- a/include/linux/nvmem-consumer.h
> +++ b/include/linux/nvmem-consumer.h
> @@ -54,6 +54,7 @@ struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *id);
>   struct nvmem_cell *devm_nvmem_cell_get(struct device *dev, const char *id);
>   void nvmem_cell_put(struct nvmem_cell *cell);
>   void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell);
> +size_t nvmem_cell_size(struct nvmem_cell *cell);
>   void *nvmem_cell_read(struct nvmem_cell *cell, size_t *len);
>   int nvmem_cell_write(struct nvmem_cell *cell, void *buf, size_t len);
>   int nvmem_cell_read_u8(struct device *dev, const char *cell_id, u8 *val);
> @@ -117,6 +118,11 @@ static inline void nvmem_cell_put(struct nvmem_cell *cell)
>   {
>   }
>   
> +static inline size_t nvmem_cell_size(struct nvmem_cell *cell)
> +{
> +	return 0;
> +}
> +
>   static inline void *nvmem_cell_read(struct nvmem_cell *cell, size_t *len)
>   {
>   	return ERR_PTR(-EOPNOTSUPP);

Hello,

On 3/7/25 12:42, Srinivas Kandagatla wrote:
> Hi Jennifer,
> 
> There is a similar patch on the list, could you take a look and see if that is usable in power reset driver.
> 
> https://lore.kernel.org/lkml/20250306093900.2199442-3-o.rempel@pengutronix.de/T/#m97bbb1870d7140661894a4e806a695e563588524
> 
> --srini

Yes, the nvmem_cell_get_size() function defined in that patch would make my own nvmem_cell_size() function in this patch redundant. I can update my reboot mode driver change to depend on that patch instead of introducing my own function for the same purpose.