On Mon, Dec 20, 2021 at 07:47:30AM +0100, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@xxxxxxxxxx>
>
> This allows reading NVMEM cells using /sys/bus/nvmem/devices/*/cells/*
> which may be helpful for userspace & debugging purposes.
>
> Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx>
> ---
> Documentation/driver-api/nvmem.rst | 11 ++++++
> drivers/nvmem/core.c | 60 ++++++++++++++++++++++++++++++
> 2 files changed, 71 insertions(+)
>
> diff --git a/Documentation/driver-api/nvmem.rst b/Documentation/driver-api/nvmem.rst
> index 287e86819640..20f7d68143be 100644
> --- a/Documentation/driver-api/nvmem.rst
> +++ b/Documentation/driver-api/nvmem.rst
> @@ -185,6 +185,17 @@ ex::
> *
> 0001000
>
> +Single cells can be read using files located at::
> +
> + /sys/bus/nvmem/devices/*/cells/*
> +
> +ex::
> +
> + hexdump -C /sys/bus/nvmem/devices/mtd0/cells/mac
> +
> + 00000000 10 7b 44 c4 8a b0 |.{D...|
> + 00000006
> +
> 7. DeviceTree Binding
> =====================
>
sysfs apis are documented in Documenatation/ABI/ not in other random
files. Please fix this.
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index 23a38dcf0fc4..785a56e33f69 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -55,6 +55,7 @@ struct nvmem_cell_entry {
> struct device_node *np;
> struct nvmem_device *nvmem;
> struct list_head node;
> + struct bin_attribute battr;
> };
>
> struct nvmem_cell {
> @@ -73,6 +74,10 @@ static LIST_HEAD(nvmem_lookup_list);
>
> static BLOCKING_NOTIFIER_HEAD(nvmem_notifier);
>
> +static int __nvmem_cell_read(struct nvmem_device *nvmem,
> + struct nvmem_cell_entry *cell,
> + void *buf, size_t *len, const char *id);
> +
> static int __nvmem_reg_read(struct nvmem_device *nvmem, unsigned int offset,
> void *val, size_t bytes)
> {
> @@ -338,8 +343,18 @@ static const struct attribute_group nvmem_bin_group = {
> .is_bin_visible = nvmem_bin_attr_is_visible,
> };
>
> +static struct bin_attribute *nvmem_cells_bin_attrs[] = {
> + NULL,
> +};
> +
> +static const struct attribute_group nvmem_cells_group = {
> + .name = "cells",
> + .bin_attrs = nvmem_cells_bin_attrs,
> +};
> +
> static const struct attribute_group *nvmem_dev_groups[] = {
> &nvmem_bin_group,
> + &nvmem_cells_group,
> NULL,
> };
>
> @@ -431,7 +446,13 @@ static struct bus_type nvmem_bus_type = {
>
> static void nvmem_cell_entry_drop(struct nvmem_cell_entry *cell)
> {
> + struct device *dev = &cell->nvmem->dev;
> +
> blocking_notifier_call_chain(&nvmem_notifier, NVMEM_CELL_REMOVE, cell);
> +
> + sysfs_remove_file_from_group(&dev->kobj, &cell->battr.attr,
> + nvmem_cells_group.name);
> +
> mutex_lock(&nvmem_mutex);
> list_del(&cell->node);
> mutex_unlock(&nvmem_mutex);
> @@ -448,11 +469,50 @@ static void nvmem_device_remove_all_cells(const struct nvmem_device *nvmem)
> nvmem_cell_entry_drop(cell);
> }
>
> +static ssize_t nvmem_cell_attr_read(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *battr, char *buf,
> + loff_t pos, size_t count)
> +{
> + struct nvmem_cell_entry *cell = container_of(battr, struct nvmem_cell_entry, battr);
> + struct nvmem_device *nvmem = cell->nvmem;
> + size_t bytes;
> + u8 *data;
> + int err;
> +
> + if (pos >= cell->bytes)
> + return 0;
> +
> + data = kzalloc(cell->bytes, GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + err = __nvmem_cell_read(nvmem, cell, data, &bytes, NULL);
> + if (!err)
> + memcpy(buf, data + pos, count - pos);
> +
> + kfree(data);
> +
> + return err ? err : bytes;
> +}
> +
> static void nvmem_cell_entry_add(struct nvmem_cell_entry *cell)
> {
> + struct device *dev = &cell->nvmem->dev;
> + int err;
> +
> mutex_lock(&nvmem_mutex);
> list_add_tail(&cell->node, &cell->nvmem->cells);
> mutex_unlock(&nvmem_mutex);
> +
> + sysfs_attr_init(&cell->battr.attr);
> + cell->battr.attr.name = cell->name;
> + cell->battr.attr.mode = 0400;
> + cell->battr.read = nvmem_cell_attr_read;
> + err = sysfs_add_bin_file_to_group(&dev->kobj, &cell->battr,
> + nvmem_cells_group.name);
Why not just use the is_bin_visible attribute instead to determine if
the attribute should be shown or not instead of having to add it
after-the-fact which will race with userspace and loose?
thanks,
greg k-h
