memoryDesc->writeBytes doesn't seem to 'write bytes'
memoryDesc->writeBytes doesn't seem to 'write bytes'
- Subject: memoryDesc->writeBytes doesn't seem to 'write bytes'
- From: Lance Drake <email@hidden>
- Date: Fri, 24 Oct 2003 14:42:32 -0600
PROBLEM:
My 'memoryDesc-> writeBytes' call seems to be working in
that the returned value is as expected but the data that
gets returned to the Userspace client is not changed.
================================================
PARTICULARS:
My driver is overriding a Type05 device READ_CD function.
After the super::READ_CD(...); call returns, I take a look
at the buffer and, under special circumstances, may decide
to change some of the data in the buffer.
I call memoryDesc->prepare(kIODirectionOutIn);
For purposes of checking on and confirming the map status,
A memoryDesc->map(0) call is made (to get the IOMemoryMap*)
and then a call to getMapOptions returns kIOMapAnywhere.
Call bytesWritten = memoryDesc->writeBytes(myOffset, myBuffer,
byteCount);
Observe that bytesWritten == byteCount; It looks like all went well.
Any ideas why the data arrives back in Userspace with no apparent
change?
Thanks for any input or suggestions,
Lance Drake
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