Messages in this thread Patch in this message | | | From | Nicholas Johnson <> | Subject | Re: [PATCH v3 2/2] nvmem: Add support for write-only instances | Date | Tue, 10 Mar 2020 01:10:24 +0000 |
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On Mon, Mar 09, 2020 at 05:50:17PM +0000, Nicholas Johnson wrote: > 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. Oops, late night. Please drop the above line if you accept this. This above line applies to patch 1/2 now.
> > Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au> > --- > drivers/nvmem/nvmem-sysfs.c | 56 +++++++++++++++++++++++++++++++------ > 1 file changed, 48 insertions(+), 8 deletions(-) > > diff --git a/drivers/nvmem/nvmem-sysfs.c b/drivers/nvmem/nvmem-sysfs.c > index 9e0c429cd..846112786 100644 > --- a/drivers/nvmem/nvmem-sysfs.c > +++ b/drivers/nvmem/nvmem-sysfs.c > @@ -196,16 +196,49 @@ 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; > + /* 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 && !nvmem->read_only) > + return config->root_only ? > + nvmem_rw_root_dev_groups : nvmem_rw_dev_groups; > > - return nvmem->read_only ? nvmem_ro_dev_groups : nvmem_rw_dev_groups; > + /* Write-only, do not honour request for global writable entry */ > + if (!nvmem->reg_read && nvmem->reg_write && !nvmem->read_only) > + return config->root_only ? nvmem_wo_root_dev_groups : NULL; > + > + return NULL; > } > > /* > @@ -224,17 +257,24 @@ 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 { > + } else if (!nvmem->reg_read && nvmem->reg_write && !nvmem->read_only) { > + if (config->root_only) > + nvmem->eeprom = bin_attr_wo_root_nvmem; > + else > + return -EPERM; > + } else if (nvmem->reg_read && nvmem->reg_write && !nvmem->read_only) { > if (config->root_only) > nvmem->eeprom = bin_attr_rw_root_nvmem; > else > nvmem->eeprom = bin_attr_rw_nvmem; > - } > + } else > + return -EPERM; > + > nvmem->eeprom.attr.name = "eeprom"; > nvmem->eeprom.size = nvmem->size; > #ifdef CONFIG_DEBUG_LOCK_ALLOC > -- > 2.25.1 >
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