diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/nvmem/nvmem.rst (renamed from Documentation/nvmem/nvmem.txt) | 112 |
1 files changed, 59 insertions, 53 deletions
diff --git a/Documentation/nvmem/nvmem.txt b/Documentation/nvmem/nvmem.rst index fc2fe4b18655..3866b6e066d5 100644 --- a/Documentation/nvmem/nvmem.txt +++ b/Documentation/nvmem/nvmem.rst @@ -1,5 +1,10 @@ - NVMEM SUBSYSTEM - Srinivas Kandagatla <srinivas.kandagatla@linaro.org> +:orphan: + +=============== +NVMEM Subsystem +=============== + + Srinivas Kandagatla <srinivas.kandagatla@linaro.org> This document explains the NVMEM Framework along with the APIs provided, and how to use it. @@ -40,54 +45,54 @@ nvmem_device pointer. nvmem_unregister(nvmem) is used to unregister a previously registered provider. -For example, a simple qfprom case: +For example, a simple qfprom case:: -static struct nvmem_config econfig = { + static struct nvmem_config econfig = { .name = "qfprom", .owner = THIS_MODULE, -}; + }; -static int qfprom_probe(struct platform_device *pdev) -{ + static int qfprom_probe(struct platform_device *pdev) + { ... econfig.dev = &pdev->dev; nvmem = nvmem_register(&econfig); ... -} + } It is mandatory that the NVMEM provider has a regmap associated with its struct device. Failure to do would return error code from nvmem_register(). Users of board files can define and register nvmem cells using the -nvmem_cell_table struct: +nvmem_cell_table struct:: -static struct nvmem_cell_info foo_nvmem_cells[] = { + static struct nvmem_cell_info foo_nvmem_cells[] = { { .name = "macaddr", .offset = 0x7f00, .bytes = ETH_ALEN, } -}; + }; -static struct nvmem_cell_table foo_nvmem_cell_table = { + static struct nvmem_cell_table foo_nvmem_cell_table = { .nvmem_name = "i2c-eeprom", .cells = foo_nvmem_cells, .ncells = ARRAY_SIZE(foo_nvmem_cells), -}; + }; -nvmem_add_cell_table(&foo_nvmem_cell_table); + nvmem_add_cell_table(&foo_nvmem_cell_table); Additionally it is possible to create nvmem cell lookup entries and register -them with the nvmem framework from machine code as shown in the example below: +them with the nvmem framework from machine code as shown in the example below:: -static struct nvmem_cell_lookup foo_nvmem_lookup = { + static struct nvmem_cell_lookup foo_nvmem_lookup = { .nvmem_name = "i2c-eeprom", .cell_name = "macaddr", .dev_id = "foo_mac.0", .con_id = "mac-address", -}; + }; -nvmem_add_cell_lookups(&foo_nvmem_lookup, 1); + nvmem_add_cell_lookups(&foo_nvmem_lookup, 1); NVMEM Consumers +++++++++++++++ @@ -99,43 +104,43 @@ read from and to NVMEM. ================================= NVMEM cells are the data entries/fields in the NVMEM. -The NVMEM framework provides 3 APIs to read/write NVMEM cells. +The NVMEM framework provides 3 APIs to read/write NVMEM cells:: -struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *name); -struct nvmem_cell *devm_nvmem_cell_get(struct device *dev, const char *name); + struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *name); + struct nvmem_cell *devm_nvmem_cell_get(struct device *dev, const char *name); -void nvmem_cell_put(struct nvmem_cell *cell); -void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell); + void nvmem_cell_put(struct nvmem_cell *cell); + void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell); -void *nvmem_cell_read(struct nvmem_cell *cell, ssize_t *len); -int nvmem_cell_write(struct nvmem_cell *cell, void *buf, ssize_t len); + void *nvmem_cell_read(struct nvmem_cell *cell, ssize_t *len); + int nvmem_cell_write(struct nvmem_cell *cell, void *buf, ssize_t len); -*nvmem_cell_get() apis will get a reference to nvmem cell for a given id, +`*nvmem_cell_get()` apis will get a reference to nvmem cell for a given id, and nvmem_cell_read/write() can then read or write to the cell. -Once the usage of the cell is finished the consumer should call *nvmem_cell_put() -to free all the allocation memory for the cell. +Once the usage of the cell is finished the consumer should call +`*nvmem_cell_put()` to free all the allocation memory for the cell. 4. Direct NVMEM device based consumer APIs ========================================== In some instances it is necessary to directly read/write the NVMEM. -To facilitate such consumers NVMEM framework provides below apis. +To facilitate such consumers NVMEM framework provides below apis:: -struct nvmem_device *nvmem_device_get(struct device *dev, const char *name); -struct nvmem_device *devm_nvmem_device_get(struct device *dev, + struct nvmem_device *nvmem_device_get(struct device *dev, const char *name); + struct nvmem_device *devm_nvmem_device_get(struct device *dev, const char *name); -void nvmem_device_put(struct nvmem_device *nvmem); -int nvmem_device_read(struct nvmem_device *nvmem, unsigned int offset, + void nvmem_device_put(struct nvmem_device *nvmem); + int nvmem_device_read(struct nvmem_device *nvmem, unsigned int offset, size_t bytes, void *buf); -int nvmem_device_write(struct nvmem_device *nvmem, unsigned int offset, + int nvmem_device_write(struct nvmem_device *nvmem, unsigned int offset, size_t bytes, void *buf); -int nvmem_device_cell_read(struct nvmem_device *nvmem, + int nvmem_device_cell_read(struct nvmem_device *nvmem, struct nvmem_cell_info *info, void *buf); -int nvmem_device_cell_write(struct nvmem_device *nvmem, + int nvmem_device_cell_write(struct nvmem_device *nvmem, struct nvmem_cell_info *info, void *buf); Before the consumers can read/write NVMEM directly, it should get hold -of nvmem_controller from one of the *nvmem_device_get() api. +of nvmem_controller from one of the `*nvmem_device_get()` api. The difference between these apis and cell based apis is that these apis always take nvmem_device as parameter. @@ -145,12 +150,12 @@ take nvmem_device as parameter. When a consumer no longer needs the NVMEM, it has to release the reference to the NVMEM it has obtained using the APIs mentioned in the above section. -The NVMEM framework provides 2 APIs to release a reference to the NVMEM. +The NVMEM framework provides 2 APIs to release a reference to the NVMEM:: -void nvmem_cell_put(struct nvmem_cell *cell); -void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell); -void nvmem_device_put(struct nvmem_device *nvmem); -void devm_nvmem_device_put(struct device *dev, struct nvmem_device *nvmem); + void nvmem_cell_put(struct nvmem_cell *cell); + void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell); + void nvmem_device_put(struct nvmem_device *nvmem); + void devm_nvmem_device_put(struct device *dev, struct nvmem_device *nvmem); Both these APIs are used to release a reference to the NVMEM and devm_nvmem_cell_put and devm_nvmem_device_put destroys the devres associated @@ -162,20 +167,21 @@ Userspace 6. Userspace binary interface ============================== -Userspace can read/write the raw NVMEM file located at -/sys/bus/nvmem/devices/*/nvmem +Userspace can read/write the raw NVMEM file located at:: + + /sys/bus/nvmem/devices/*/nvmem -ex: +ex:: -hexdump /sys/bus/nvmem/devices/qfprom0/nvmem + hexdump /sys/bus/nvmem/devices/qfprom0/nvmem -0000000 0000 0000 0000 0000 0000 0000 0000 0000 -* -00000a0 db10 2240 0000 e000 0c00 0c00 0000 0c00 -0000000 0000 0000 0000 0000 0000 0000 0000 0000 -... -* -0001000 + 0000000 0000 0000 0000 0000 0000 0000 0000 0000 + * + 00000a0 db10 2240 0000 e000 0c00 0c00 0000 0c00 + 0000000 0000 0000 0000 0000 0000 0000 0000 0000 + ... + * + 0001000 7. DeviceTree Binding ===================== |