In addition to statically allocated memory ranges, they may also be
a desire to use dynamically allocated regions in a user space driver.
In particular, being able to access memory made available through the
dma-mapping API, may be particularly useful. The
uio_dmem_genirq driver provides a way to accomplish
this.
This driver is used in a similar manner to the
"uio_pdrv_genirq" driver with respect to interrupt
configuration and handling.
Set the .name element of
struct platform_device to
"uio_dmem_genirq" to use this driver.
When using this driver, fill in the .platform_data
element of struct platform_device, which is of type
struct uio_dmem_genirq_pdata and which contains the
following elements:
struct uio_info uioinfo: The same
structure used as the uio_pdrv_genirq platform
data
unsigned int *dynamic_region_sizes:
Pointer to list of sizes of dynamic memory regions to be mapped into
user space.
unsigned int num_dynamic_regions:
Number of elements in dynamic_region_sizes array.
The dynamic regions defined in the platform data will be appended to
the mem[] array after the platform device
resources, which implies that the total number of static and dynamic
memory regions cannot exceed MAX_UIO_MAPS.
The dynamic memory regions will be allocated when the UIO device file,
/dev/uioX is opened.
Similar to static memory resources, the memory region information for
dynamic regions is then visible via sysfs at
/sys/class/uio/uioX/maps/mapY/*.
The dynamic memory regions will be freed when the UIO device file is
closed. When no processes are holding the device file open, the address
returned to userspace is ~0.