Messages in this thread Patch in this message | | | From | Nicholas Johnson <> | Subject | [PATCH v2 1/3] nvmem: Add support for write-only instances | Date | Mon, 2 Mar 2020 15:42:34 +0000 |
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There is at least one real-world use-case for write-only nvmem instances. Refer to 03cd45d2e219 ("thunderbolt: Prevent crash if non-active NVMem file is read").
Add support for write-only nvmem instances by adding attrs for 0200.
Change nvmem_register() to abort if NULL group is returned from nvmem_sysfs_get_groups().
Return NULL from nvmem_sysfs_get_groups() in invalid cases.
Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au> --- drivers/nvmem/core.c | 2 ++ drivers/nvmem/nvmem-sysfs.c | 53 ++++++++++++++++++++++++++++++++----- 2 files changed, 48 insertions(+), 7 deletions(-)
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index ef326f243..27bd4c4e3 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -388,6 +388,8 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) config->read_only || !nvmem->reg_write; nvmem->dev.groups = nvmem_sysfs_get_groups(nvmem, config); + if (!nvmem->dev.groups) + return NULL; device_initialize(&nvmem->dev); diff --git a/drivers/nvmem/nvmem-sysfs.c b/drivers/nvmem/nvmem-sysfs.c index 9e0c429cd..00d3259ea 100644 --- a/drivers/nvmem/nvmem-sysfs.c +++ b/drivers/nvmem/nvmem-sysfs.c @@ -196,16 +196,50 @@ static const struct attribute_group *nvmem_ro_root_dev_groups[] = { NULL, }; +/* write only permission, root only */ +static struct bin_attribute bin_attr_wo_root_nvmem = { + .attr = { + .name = "nvmem", + .mode = 0200, + }, + .write = bin_attr_nvmem_write, +}; + +static struct bin_attribute *nvmem_bin_wo_root_attributes[] = { + &bin_attr_wo_root_nvmem, + NULL, +}; + +static const struct attribute_group nvmem_bin_wo_root_group = { + .bin_attrs = nvmem_bin_wo_root_attributes, + .attrs = nvmem_attrs, +}; + +static const struct attribute_group *nvmem_wo_root_dev_groups[] = { + &nvmem_bin_wo_root_group, + NULL, +}; + const struct attribute_group **nvmem_sysfs_get_groups( struct nvmem_device *nvmem, const struct nvmem_config *config) { - if (config->root_only) - return nvmem->read_only ? - nvmem_ro_root_dev_groups : - nvmem_rw_root_dev_groups; - - return nvmem->read_only ? nvmem_ro_dev_groups : nvmem_rw_dev_groups; + /* Read-only */ + if (nvmem->reg_read && (!nvmem->reg_write || nvmem->read_only)) + return config->root_only ? + nvmem_ro_root_dev_groups : nvmem_ro_dev_groups; + + /* Read-write */ + if (nvmem->reg_read && nvmem->reg_write) + return config->root_only ? + nvmem_rw_root_dev_groups : nvmem_rw_dev_groups; + + /* Write-only, do not honour request for global writable entry */ + if (!nvmem->reg_read && nvmem->reg_write) + return config->root_only ? nvmem_wo_root_dev_groups : NULL; + + /* Neither reg_read nor reg_write are provided, abort */ + return NULL; } /* @@ -224,11 +258,16 @@ int nvmem_sysfs_setup_compat(struct nvmem_device *nvmem, if (!config->base_dev) return -EINVAL; - if (nvmem->read_only) { + if (nvmem->reg_read && (!nvmem->reg_write || nvmem->read_only)) { if (config->root_only) nvmem->eeprom = bin_attr_ro_root_nvmem; else nvmem->eeprom = bin_attr_ro_nvmem; + } else if (!nvmem->reg_read && nvmem->reg_write) { + if (config->root_only) + nvmem->eeprom = bin_attr_wo_root_nvmem; + else + return -EPERM; } else { if (config->root_only) nvmem->eeprom = bin_attr_rw_root_nvmem; -- 2.25.1
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