Chapter 2. API Reference
esp_vfs_t myfs = {
.flags = ESP_VFS_FLAG_DEFAULT,
.write = &myfs_write,
.open = &myfs_open,
.fstat = &myfs_fstat,
.close = &myfs_close,
.read = &myfs_read,
};
ESP_ERROR_CHECK(esp_vfs_register("/data", &myfs, NULL));
Depending on the way how the FS driver declares its API functions, either read, write, etc., or read_p,
write_p, etc., should be used.
Case 1: API functions are declared without an extra context pointer (the FS driver is a singleton):
ssize_t myfs_write(int fd, const void * data, size_t size);
// In definition of esp_vfs_t:
.flags = ESP_VFS_FLAG_DEFAULT,
.write = &myfs_write,
// ... other members initialized
// When registering FS, context pointer (third argument) is NULL:
ESP_ERROR_CHECK(esp_vfs_register("/data", &myfs, NULL));
Case 2: API functions are declared with an extra context pointer (the FS driver supports multiple instances):
ssize_t myfs_write(myfs_t* fs, int fd, const void * data, size_t size);
// In definition of esp_vfs_t:
.flags = ESP_VFS_FLAG_CONTEXT_PTR,
.write_p = &myfs_write,
// ... other members initialized
// When registering FS, pass the FS context pointer into the third argument
// (hypothetical myfs_mount function is used for illustrative purposes)
myfs_t* myfs_inst1 = myfs_mount(partition1->offset, partition1->size);
ESP_ERROR_CHECK(esp_vfs_register("/data1", &myfs, myfs_inst1));
// Can register another instance:
myfs_t* myfs_inst2 = myfs_mount(partition2->offset, partition2->size);
ESP_ERROR_CHECK(esp_vfs_register("/data2", &myfs, myfs_inst2));
Synchronous input/output multiplexing Synchronous input/output multiplexing by select() is supported in
the VFS component. The implementation works in the following way.
1. select() is called with file descriptors which could belong to various VFS drivers.
2. The file descriptors are divided into groups each belonging to one VFS driver.
3. The file descriptors belonging to non-socket VFS drivers are handed over to the given VFS drivers by
start_select() described later on this page. This function represents the driver-specific implementa-
tion of select() for the given driver. This should be a non-blocking call which means the function should
immediately return after setting up the environment for checking events related to the given file descriptors.
4. The file descriptors belonging to the socket VFS driver are handed over to the socket driver by
socket_select() described later on this page. This is a blocking call which means that it will return
only if there is an event related to socket file descriptors or a non-socket driver signals socket_select()
to exit.
5. Results are collected from each VFS driver and all drivers are stopped by deinitiazation of the environment for
checking events.
6. The select() call ends and returns the appropriate results.
Espressif Systems 769
Submit Document Feedback
Release v4.4
To Next Page
Loading...
Need help?
General