Re: IOUserClient size limit?

Subject: Re: IOUserClient size limit?

From: Chris Sarcone <email@hidden>

Date: Mon, 10 Nov 2008 16:53:42 -0800

Delivered-to: email@hidden

Duane --

I am seeing a kIOReturnIPCError form an IOUserClient down call (i.e.
from my app into the kernel) when I have a structure that is over 4K
(4096) bytes in size.

Is this a hard limit? Can I change this limit? I have some I/O through
the user client that I would like to take a larger buffer (16K).

Yes, it's a hard limit for IPC.

Typically, you solve this by:

1) Save the task_t passed to your user client in initWithTask().

2) Pass a pointer to the large buffer and use IOMD::withAddressRange() (which takes the task_t parameter)

3) prepare() it

4) Use it for DMA in conjunction with an IODMACommand or use readBytes()/writeBytes()

5) complete() it

6) release the IOMD

HTH,

-- Chris

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Follow-Ups:

Re: IOUserClient size limit?
- From: "Duane Murphy" <email@hidden>

References:

>IOUserClient size limit? (From: "Duane Murphy" <email@hidden>)