116 lines
3.1 KiB
Plaintext
116 lines
3.1 KiB
Plaintext
Introduction
|
|
============
|
|
|
|
This is a new platform driver for newly introduced UIO devices
|
|
to facilitate clients in Userspace.
|
|
|
|
Hardware description
|
|
====================
|
|
This driver does not implement any specific hardware driver.
|
|
|
|
Software description
|
|
====================
|
|
|
|
Design
|
|
======
|
|
|
|
The goal of this driver is to ensure there is no security lapse in the
|
|
Userspace clients' functionality. This new driver uses the existing
|
|
UIO framework to facilitate the clients to be able to memory map their
|
|
respective allotted shared memory address in the client's address space.
|
|
|
|
|
|
|
Userspace | Kernel space
|
|
+--------------+ +---------------+ +---------------+
|
|
| Client | | Shared | | shrdmem_uio |
|
|
| <-------> Memory <-------> driver |
|
|
+--------------+ +---------------+ +---------------+
|
|
|
|
|
|
|
|
|
|
The shared memory (a transport buffer) address is unique for each
|
|
individual client and is made available to the driver via device tree.
|
|
|
|
For a given client the probe would be called once in the shrdmem_uio driver.
|
|
This driver would parse the device tree and register a new UIO device with kernel
|
|
available under /dev/uioX (where X would start from zero, being serially
|
|
incremented for the next UIO device probed)
|
|
|
|
The client in Userspace would be able to access the respective UIO device
|
|
under the sysfs entry(/sys/class/uio/uioX) upon verifying the name and version
|
|
of the device under this sysfs node. Once verified it could access the physical
|
|
address under /sys/class/uio/uioX/maps/map0/addr
|
|
|
|
The client would request for memory mapping which would be taken care of in the
|
|
kernel space by the UIO framework. No explicit mmap() implementation required by
|
|
the shrdmem_uio driver.
|
|
|
|
Power Management
|
|
================
|
|
Does not implement any power management.
|
|
|
|
SMP/multi-core
|
|
==============
|
|
|
|
The platform driver would be loaded/probed once per client.
|
|
DTS files will be looked up for shared memory addresses and sizes for all the clients.
|
|
The UIO char device will be created under /dev/uioX.
|
|
|
|
This being one time activity for a given client it does not require SMP/multi-core safety.
|
|
|
|
Security
|
|
========
|
|
|
|
The devices (/dev/uioX) would have permission checks for restricted access
|
|
|
|
Performance
|
|
===========
|
|
|
|
None.
|
|
|
|
Interface
|
|
=========
|
|
|
|
This driver does not export any APIs for kernel.
|
|
Android user space can access the shared memory by mmaping it.
|
|
|
|
Driver parameters
|
|
=================
|
|
|
|
None.
|
|
|
|
Config options
|
|
==============
|
|
|
|
None.
|
|
|
|
Dependencies
|
|
============
|
|
|
|
The only dependency is the kernel device tree files for the
|
|
Userspace client details.
|
|
|
|
User space utilities
|
|
====================
|
|
This driver communicates with the following user space clients/utilities:
|
|
|
|
Remote File System:
|
|
- Based on Qualcomm Messaging Interface (QMI)
|
|
- This service enables the modules on the MSM modem processor to
|
|
read data from and write data to the embedded multimedia card (eMMC),
|
|
which is solely controlled by the applications processor.
|
|
|
|
Remote File System Access (QMI_RFSA):
|
|
- Based on Qualcomm Messaging Interface (QMI)
|
|
- This service provides access from the Hexagon processor to a High-Level
|
|
Operating Sytem (HLOS) file system
|
|
Other
|
|
=====
|
|
|
|
None.
|
|
|
|
Known issues
|
|
============
|
|
|
|
None.
|