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Problem with too big data buffer in DEVCTL
OpenQNX Forum Index » General » QNX Newsgroups » qnx.ddk
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juro
Post subject: Problem with too big data buffer in DEVCTL  PostPosted: Oct 01, 2007 - 01:13 PM
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Joined: Sep 18, 2007
Posts: 3
Hello,
it is possible to send data buffer with size about 1MB with using DEVCTL?
Or how to send such mount of data between resmgr and client?
Thanks
Juraj
 
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async
Post subject: RE: Problem with too big data buffer in DEVCTL  PostPosted: Oct 03, 2007 - 02:06 PM
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Joined: Sep 16, 2007
Posts: 3
MsgSend() is used to transfer the data, and the maximum size for one-part message-pass is 2^32 - 1 (SSIZE_MAX). If you want to avoid copying the data in the buffer, you can use MsgRead () / MsgWrite () to read data from the client's address.

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stefano
 
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David Gibbs
Post subject: Re: Problem with too big data buffer in DEVCTL  PostPosted: Oct 09, 2007 - 09:03 PM
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juro <juraj.frank@naex-dot-sk.no-spam.invalid> wrote:
Quote:
Hello,
it is possible to send data buffer with size about 1MB with using
DEVCTL?

Yes, the API will happily transfer any size of buffer up to the
maximum that can be sent.

Quote:
Or how to send such mount of data between resmgr and client?

MsgSend() (the underlying kernel call) uses signed 32-bit integers
for message lengths. This suggests the maximum transfer would be
2G -- for a devctl() it would be 2G-sizeof(devctl header).

-David
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David Gibbs
QNX Training Services
dagibbs@qnx.com
 
   
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David Gibbs
Post subject: Re: Problem with too big data buffer in DEVCTL  PostPosted: Oct 09, 2007 - 09:04 PM
Guest
async <asreti@gmail-dot-com.no-spam.invalid> wrote:
Quote:
MsgSend() is used to transfer the data, and the maximum size for
one-part message-pass is 2^32 - 1 (SSIZE_MAX). If you want to avoid
copying the data in the buffer, you can use MsgRead () / MsgWrite ()
to read data from the client's address.

MsgSend() takes signed ints for the lengths. This suggests 2^31, rather
than 2^32.

-David
--
David Gibbs
QNX Training Services
dagibbs@qnx.com
 
   
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