Messages in this thread Patch in this message |  | | From | Nicholas Johnson <> | Subject | [PATCH v1 1/3] nvmem: Add support for write-only instances | Date | Mon, 24 Feb 2020 17:42:33 +0000 |
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Mika Westerberg requires write-only nvmem for the Thunderbolt driver. Refer to 03cd45d2e219 ("thunderbolt: Prevent crash if non-active NVMem file is read"). Hence, there is at least one real-world use for write-only nvmem instances.
Add support for write-only nvmem instances by changing the nvmem attrs to 0222 if the .reg_read callback is not populated.
Add a WARN_ON in case a driver populates neither .reg_read nor .reg_write because this behaviour should clearly never occur.
Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au> --- drivers/nvmem/nvmem-sysfs.c | 77 +++++++++++++++++++++++++++++++++---- 1 file changed, 70 insertions(+), 7 deletions(-)
diff --git a/drivers/nvmem/nvmem-sysfs.c b/drivers/nvmem/nvmem-sysfs.c index 9e0c429cd..be3b94f0b 100644 --- a/drivers/nvmem/nvmem-sysfs.c +++ b/drivers/nvmem/nvmem-sysfs.c @@ -147,6 +147,30 @@ static const struct attribute_group *nvmem_ro_dev_groups[] = { NULL, }; +/* write only permission */ +static struct bin_attribute bin_attr_wo_nvmem = { + .attr = { + .name = "nvmem", + .mode = 0222, + }, + .write = bin_attr_nvmem_write, +}; + +static struct bin_attribute *nvmem_bin_wo_attributes[] = { + &bin_attr_wo_nvmem, + NULL, +}; + +static const struct attribute_group nvmem_bin_wo_group = { + .bin_attrs = nvmem_bin_wo_attributes, + .attrs = nvmem_attrs, +}; + +static const struct attribute_group *nvmem_wo_dev_groups[] = { + &nvmem_bin_wo_group, + NULL, +}; + /* default read/write permissions, root only */ static struct bin_attribute bin_attr_rw_root_nvmem = { .attr = { @@ -196,16 +220,50 @@ 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; + /* + * If neither reg_read nor reg_write are provided, we cannot use this + * nvmem entry, as any operation will cause kernel mode NULL reference. + */ + WARN_ON(!nvmem->reg_read && !nvmem->reg_write); + + if (nvmem->reg_read && nvmem->reg_write) + return config->root_only ? + nvmem_rw_root_dev_groups : nvmem_rw_dev_groups; + + if (nvmem->reg_read && !nvmem->reg_write) + return config->root_only ? + nvmem_ro_root_dev_groups : nvmem_ro_dev_groups; + + return config->root_only ? + nvmem_wo_root_dev_groups : nvmem_wo_dev_groups; } /* @@ -224,11 +282,16 @@ 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) { 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 + nvmem->eeprom = bin_attr_wo_nvmem; } else { if (config->root_only) nvmem->eeprom = bin_attr_rw_root_nvmem; -- 2.25.1
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