Disk Access¶
Overview¶
The disk access API provides access to storage devices.
SD Card support¶
Zephyr has support for some SD card controllers and support for interfacing SD cards via SPI. These drivers use disk driver interface and a file system can access the SD cards via disk access API. Both standard and high-capacity SD cards are supported.
Note
The system does not support inserting or removing cards while the system is running. The cards must be present at boot and must not be removed. This may be fixed in future releases.
FAT filesystems are not power safe so the filesystem may become corrupted if power is lost or if the card is removed.
SD Card support via SPI¶
Example devicetree fragment below shows how to add SD card node to spi1
interface. Example uses pin PA27 for chip select, and runs the SPI bus
at 24 MHz once the SD card has been initialized:
&spi1 {
status = "okay";
cs-gpios = <&porta 27 GPIO_ACTIVE_LOW>;
sdhc0: sdhc@0 {
compatible = "zephyr,mmc-spi-slot";
reg = <0>;
status = "okay";
label = "SDHC0";
spi-max-frequency = <24000000>;
};
};
The SD card will be automatically detected and initialized by the filesystem driver when the board boots.
To read and write files and directories, see the File Systems in
include/fs.h such as fs_open(),
fs_read(), and fs_write().
API Reference¶
-
group
disk_access_interface Disk Access APIs.
Functions
-
int
disk_access_init(const char *pdrv)¶ perform any initialization
This call is made by the consumer before doing any IO calls so that the disk or the backing device can do any initialization.
- Parameters
pdrv – [in] Disk name
- Returns
0 on success, negative errno code on fail
-
int
disk_access_status(const char *pdrv)¶ Get the status of disk.
This call is used to get the status of the disk
- Parameters
pdrv – [in] Disk name
- Returns
DISK_STATUS_OK or other DISK_STATUS_*s
-
int
disk_access_read(const char *pdrv, uint8_t *data_buf, uint32_t start_sector, uint32_t num_sector)¶ read data from disk
Function to read data from disk to a memory buffer.
- Parameters
pdrv – [in] Disk name
data_buf – [in] Pointer to the memory buffer to put data.
start_sector – [in] Start disk sector to read from
num_sector – [in] Number of disk sectors to read
- Returns
0 on success, negative errno code on fail
-
int
disk_access_write(const char *pdrv, const uint8_t *data_buf, uint32_t start_sector, uint32_t num_sector)¶ write data to disk
Function write data from memory buffer to disk.
- Parameters
pdrv – [in] Disk name
data_buf – [in] Pointer to the memory buffer
start_sector – [in] Start disk sector to write to
num_sector – [in] Number of disk sectors to write
- Returns
0 on success, negative errno code on fail
-
int
disk_access_ioctl(const char *pdrv, uint8_t cmd, void *buff)¶ Get/Configure disk parameters.
Function to get disk parameters and make any special device requests.
- Parameters
pdrv – [in] Disk name
cmd – [in] DISK_IOCTL_* code describing the request
buff – [in] Command data buffer
- Returns
0 on success, negative errno code on fail
-
int
Disk Driver Interface¶
-
group
disk_driver_interface Disk Driver Interface.
Defines
-
DISK_IOCTL_GET_SECTOR_COUNT¶ Possible Cmd Codes for disk_ioctl()
Get the number of sectors in the disk
-
DISK_IOCTL_GET_SECTOR_SIZE¶ Get the size of a disk SECTOR in bytes
-
DISK_IOCTL_RESERVED¶ reserved. It used to be DISK_IOCTL_GET_DISK_SIZE
-
DISK_IOCTL_GET_ERASE_BLOCK_SZ¶ How many sectors constitute a FLASH Erase block
-
DISK_IOCTL_CTRL_SYNC¶ Commit any cached read/writes to disk
-
DISK_STATUS_OK¶ Possible return bitmasks for disk_status()
Disk status okay
-
DISK_STATUS_UNINIT¶ Disk status uninitialized
-
DISK_STATUS_NOMEDIA¶ Disk status no media
-
DISK_STATUS_WR_PROTECT¶ Disk status write protected
Functions
-
struct
disk_info¶ - #include <disk.h>
Disk info.
Public Members
-
sys_dnode_t
node¶ Internally used list node
-
char *
name¶ Disk name
-
const struct disk_operations *
ops¶ Disk operations
-
sys_dnode_t
-
struct
disk_operations¶ - #include <disk.h>
Disk operations.
-