What is a mailbox in programming terms?

Phishfry

Phishfry

I see the term mailbox pop up all over. Mostly on Arm.

I also saw it on Video Output for an Arm board. Video mailbox I think it was called.

Is it computer slang or defined? I am not talking about e-mail or mail services.

The request is done through the HPS-SDM mailbox.
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Single Image Boot

This document describes what is a Single Image Boot and the updates done to support it.
www.rocketboards.org www.rocketboards.org
 
Phishfry said:
I see the term mailbox pop up all over. Mostly on Arm.
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It is a hardware mechanism to allow cores to "talk" to each other. The mailbox analogy is appropriate. The "sending" core puts a "message" into a mailbox. The meaning of that message is defined by mutual agreement of the sender and receiver. The "receiving" core is interrupted to indicate the presence of that message, which it then retrieves and interprets.

Such a mechanism is typically used for TLB shootdowns, cache consistency, etc. -- any time two concurrently executing cores have to agree on the state of the hardware and the processes running in it.
 
Jose said:
a form of inter-process communication
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No, interprocessOR communication. It addresses the fact that two or more real processors are concurrently executing so a hardware mechanism to connect them is required.

IPC doesn't require any special hardware, just some set of conventions that THE processor observes to pass information between the processes that it manages.
 
Here in the video context. I thought maybe it was from assembly code.

The Mailbox Peripheral

Mailbox Overview The Mailbox Peripheral is a peripheral that facilitates communication between the ARM CPU and the VideoCore GPU. It starts at offset 0xB880 and has three relevent registers. The Read register is at offset 0x00 from the mailbox base, and facilitates reading messages from the GPU...
jsandler18.github.io
 
Don Y said:
No, interprocessOR communication. It addresses the fact that two or more real processors are concurrently executing so a hardware mechanism to connect them is required.

IPC doesn't require any special hardware, just some set of conventions that THE processor observes to pass information between the processes that it manages.
Click to expand...
The term mailbox is also used in inter-process (or multi-threaded or distributed) system design, along with terms such as queue, lock, semaphore.
 
ralphbsz said:
The term mailbox is also used in inter-process (or multi-threaded or distributed) system design, along with terms such as queue, lock, semaphore.
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The OP mentioned ARM; there, mailboxes are a distinct hardware mechanism designed for interprocessor communication. In a single processor (core) scenario, THE ONE processor knows when it wants to exchange information between processes so no special hardware is required.
 
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