On Thu, Jun 13, 2024 at 03:15:29PM +0200, Marco Felsch wrote:
> Expose the nvmem cells via cdevs which is our equivalent to the Linux
> sysfs exposure. This allows the easier user queries for board code and
> shell. Keep the Linux function name scheme for
> nvmem_populate_sysfs_cells() to reduce the diff for nvmem_register()
> function.
>
> Signed-off-by: Marco Felsch <m.felsch@xxxxxxxxxxxxxx>
> ---
> v2:
> - fix error handling path during nvmem_register
> - drop useless list_empty()
>
> drivers/nvmem/core.c | 101 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 101 insertions(+)
>
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index ee7d4c6301c3..8e91d9c0fc8a 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -44,6 +44,8 @@ struct nvmem_cell_entry {
> struct device_node *np;
> struct nvmem_device *nvmem;
> struct list_head node;
> +
> + struct cdev cdev;
> };
>
> struct nvmem_cell {
> @@ -144,6 +146,101 @@ static struct nvmem_device *of_nvmem_find(struct device_node *nvmem_np)
> return NULL;
> }
>
> +static struct nvmem_cell *nvmem_create_cell(struct nvmem_cell_entry *entry,
> + const char *id, int index);
> +
> +static ssize_t nvmem_cell_cdev_read(struct cdev *cdev, void *buf, size_t count,
> + loff_t offset, unsigned long flags)
> +{
> + struct nvmem_cell_entry *entry;
> + struct nvmem_cell *cell = NULL;
> + size_t cell_sz, read_len;
> + void *content;
> +
> + entry = container_of(cdev, struct nvmem_cell_entry, cdev);
> + cell = nvmem_create_cell(entry, entry->name, 0);
> + if (IS_ERR(cell))
> + return PTR_ERR(cell);
> +
> + content = nvmem_cell_read(cell, &cell_sz);
> + if (IS_ERR(content)) {
> + read_len = PTR_ERR(content);
> + goto destroy_cell;
> + }
> +
> + read_len = min_t(unsigned int, cell_sz - offset, count);
> + memcpy(buf, content + offset, read_len);
> + kfree(content);
> +
> +destroy_cell:
> + kfree_const(cell->id);
> + kfree(cell);
> +
> + return read_len;
> +}
> +
> +static ssize_t nvmem_cell_cdev_write(struct cdev *cdev, const void *buf, size_t count,
> + loff_t offset, unsigned long flags)
> +{
> + struct nvmem_cell_entry *entry;
> + struct nvmem_cell *cell;
> + int ret;
> +
> + entry = container_of(cdev, struct nvmem_cell_entry, cdev);
> +
> + if (!entry->nvmem->reg_write)
> + return -EPERM;
> +
> + if (offset >= entry->bytes)
> + return -EFBIG;
> +
> + if (offset + count > entry->bytes)
> + count = entry->bytes - offset;
> +
> + cell = nvmem_create_cell(entry, entry->name, 0);
> + if (IS_ERR(cell))
> + return PTR_ERR(cell);
> +
> + if (!cell)
> + return -EINVAL;
> +
> + ret = nvmem_cell_write(cell, buf, count);
> +
> + kfree_const(cell->id);
> + kfree(cell);
> +
> + return ret;
> +}
> +
> +static struct cdev_operations nvmem_cell_chrdev_ops = {
> + .read = nvmem_cell_cdev_read,
> + .write = nvmem_cell_cdev_write,
> +};
> +
> +static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
> +{
> + struct device *dev = &nvmem->dev;
> + struct nvmem_cell_entry *entry;
> +
> + list_for_each_entry(entry, &nvmem->cells, node) {
> + struct cdev *cdev;
> + int ret;
> +
> + cdev = &entry->cdev;
> + cdev->name = xasprintf("%s.%s", dev_name(dev),
> + kbasename(entry->name));
> + cdev->ops = &nvmem_cell_chrdev_ops;
> + cdev->dev = dev;
> + cdev->size = entry->bytes;
> +
> + ret = devfs_create(cdev);
> + if (ret)
> + return ret;
You might fail here without unregistering the already registered cells.
Furthermore you free the nvmem device which likely leads to memory
corruptions further down. Your choices are:
- Do not fail here, but only print a warning when devfs_create() fails,
or:
- properly unregister what you registered beforehand.
Sascha
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