The interface from the hardware specific driver to the hardware
independent driver is contained in a disk_callbacks_t
structure. A pointer to this is automatically included into the disk
channel structure callbacks field by the
DISK_CHANNEL() macro. The
disk_callbacks_t structure contains the following
This is called when a valid disk device has been recognised on the
given disk channel. At this point, if the disk supports partitioning
the disk's partition table will be read and the partitions determined.
This may be called either from the driver's init routine, for fixed
disks, or alternatively from the driver's lookup routine. It may also
be called from other places when, for example, disk insertion is
detected. All the fields of the ident structure
must be filled in by the driver before this call is made.
This must be called from the driver's lookup function to complete the
lookup process. It is here that the interpretation of the partition
number element of the device name is done and a new devtab entry
created for the partition if necessary.
When the call to the read() or
write() disk function returns
-EWOULDBLOCK then the driver must indicate
completion of the actual transfer by calling this function. This
function should not be called from an ISR, but it may be called from
In addition to these functions in disk_callbacks_t, the
hardware driver is also responsible for calling the disk event
callback. The calls should be made as follows:
disk_channel *chan = <get pointer to disk channel>;
chan->event( CYG_DISK_EVENT_CONNECT, devno, chan->event_data );
The first argument should be the event being notified:
CYG_DISK_EVENT_CONNECT as shown here, or
CYG_DISK_EVENT_DISCONNECT. The second argument is a
device number; this is needed for devices that dynamically instantiate
disk devices, such as USB. If the driver does not do this, then this
argument should be -1. The third argument is the user data value
passed in when the callback was registered.
The driver may call this function at any time and from any context
other than an ISR. Normally it will be called either from a DSR or
from a thread context. By default, the generic disk layer will install
a dummy function in the disk channel structure, so the driver can
always make the call without needing to test for a NULL pointer. A
CONNECT event call should be made when the driver detects that a new
device has been inserted into the drive, and an DISCONNECT event call
should be made when the device is removed.
A CONNECT event call should also be made if a disk device is already
connected when the driver observes the application registering for
notification of disk events by use of the
CYG_IO_SET_CONFIG_DISK_EVENTcyg_io_set_config() operation. However, this only
applies to connected disks - the driver does not indicate DISCONNECT events
for unconnected disks.