Printable View
Good day,
I have read that the file server in the user space can access the local media LDD in the kernel space, which in turn can interact with the PDDs like the nand media driver.
Can we access the ram by accessing the local media LDD (ELOCD.LDD)?
Is the ram registered with the LDD?
If we cannot do that, how then could we access the ram?
Thanks in advance.
As far I know, a user-mode app can only access virtual memory addresses (of its own process), and not [D]RAM directly. You'd need to be able to write and install kernel-mode code (such as a device driver) to bypass that, and Nokia's Symbian phones does not allow user-installable arbitrary device drivers.
Note that the Wiki contains the complete book "Symbian OS Internals", [url]http://www.developer.nokia.com/Community/Wiki/Symbian_OS_Internals[/url]
It should provide some details about memory management and the driver model.
Good day,
thanks for the replies.
Another question is that is the Internal Ram different from the Dram that is used as the memory?
When we refer to physical memory, we are referring to the Dram?
Thanks.
Phones usually have both DRAM and NAND Flash.
The NAND Flash is divided to ROM (firmware, Z-drive, not writable), and writable, non-volatile phone storage memory (C-drive). There may be also a separate Flash memory as internal "mass storage", the E-drive). If there is no internal mass storage, an external memory card may be supported (E-drive, if no internal mass storage, and F-drive if internal mass storage is E).
DRAM is allocated in a single-CPU device to the telephony software (usually a fixed block taken from the higher addresses, in the case of Nokia phones about), and the rest (most of it) is given to the application OS (Symbian).
Symbian also allocates a chunk of DRAM to a RAM drive (D-drive) for temporary files/content (lost at reboot).
[QUOTE=mouse_321;859387]Another question is that is the Internal Ram different from the Dram that is used as the memory?
When we refer to physical memory, we are referring to the Dram?[/QUOTE]In the everyday context, all "internal RAM", DRAM, "physical memory" are referring the same thing, the actual operating memory of a given system, with (more or less) direct read-write access by the CPU.
[QUOTE=wizard_hu_;859392]In the everyday context, all "internal RAM", DRAM, "physical memory" are referring the same thing, the actual operating memory of a given system, with (more or less) direct read-write access by the CPU.[/QUOTE]
Not necessarily... True - RAM, DRAM - refers to the same memory, which is usually SDRAM (LPDDR or LPDDR2 these days). This is the memory, that is physically connected to the SoC and controlled using memory controller (DMC - dynamic memory controller). Some controllers allow interfaces to other types of memory (NAND, NVRAM, SDRAM etc.).
But internal RAM is a static RAM that lives on the SoC itself (this is why it's called internal). SymbianOS does not generally make use of this memory, so no mapping exists. One of exceptions, when this memory is used is during RAM defrag, but this has to be implemented by the baseport. In such case - internal RAM is accessed from low-level code directly- program that executes the defragmentation has to be copied there to ensure, that it will be able to execute correctly whilst external memory is manipulated.
mouse_321 - what is the reason for using this internal memory anyway? Why are you asking this?
[QUOTE=mouse_321;859387]
When we refer to physical memory, we are referring to the Dram?
[/QUOTE]
Most likely we do. Also, of course - referring to physical memory means that we are accessing it using a physical address instead of virtual one. (google for virtual memory if you're not familiar with this).