Re: Read through Filter Scheme Driver

12 May 2005

      site_archiver@lists.apple.com
Delivered-To: darwin-kernel@lists.apple.com

Hi Imran,
    IOLog("\n Calling read routine of driver.....\n");
    getProvider()->read(client, 0, OutBuffer, completion);
    IOLog("\n Called read routine of driver.....\n");

Dan
On 11 May 2005, at 8:31 AM, Imran Kazi wrote:
Dear Mike,
Please go through the below code for our Read issue
/***************User Space Application **************************/
/* Purpose: This calls the 'read' method of user client using
IOConnectMethodStructureIStructureO */
static kern_return_t MyDoRead(io_connect_t connect)
    kern_return_t    kernResult;
    MySampleStruct   sampleStructIn;  // Input structure
    MySampleStruct   sampleStructOut; //Output structure
    kernResult = vm_allocate(mach_task_self(), (vm_address_t*)
&sampleStructIn.buff, vm_page_size, TRUE);
    if(sampleStructIn.buff)
    {
           char* buff = (char*) sampleStructOut.buff;
           strcpy(buff, "");
    }
    IOByteCount structSizeIn = sizeof(MySampleStruct);
        IOByteCount structSizeOut = sizeof(MySampleStruct);
        if(retRead == kIOReturnSuccess)
        {
            IOLog("\n prepare for buff Succeded....\n");
        // mapping the IOMemoryDescriptr buffer
            retRead = ReadBuffer->map();
            retRead = UCProvider->CoreSnapDriverDoRead(this, 512,
ReadBuffer, completion);
    IOByteCount readBytes;
    IOByteCount requestByteCount = 0;
    IOReturn status = 0;
    IOByteCount bufLength = OutBuffer->getLength();
    char *myBuff = new char[bufLength];
    readBytes = OutBuffer->readBytes(0, myBuff, bufLength);
    // Make "filter" changes to the buffer here.
    IOLog("\n Calling read routine of driver.....\n");
    getProvider()->read(client, 0, OutBuffer, completion);
    IOLog("\n Called read routine of driver.....\n");
    IOLog("\n Calling readbytes.......in driver\n");
    readBytes = OutBuffer->readBytes(0, myBuff, bufLength);
    IOLog("\n Calling complete routine of driver......\n");
    getProvider()->complete(completion, status, requestByteCount);
    IOLog("\n Called complete routine of driver......\n");
    delete[] myBuff;
    return  retDrRead;
}
Do we need to call withAddress() and prepare() and map() the
IOMemoryDescriptor before passing it to standard read() method.

Thanks
Imran

This email sent to markarian@apple.com

_______________________________________________
Do not post admin requests to the list. They will be ignored.
Darwin-kernel mailing list      (Darwin-kernel@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.a...

You made an asynchronous request.  You must wait until the completion
routine you pass in fires before you may access the result.  You are
welcome to make a synchronous request in case that was your
intention.  You do not require a completion routine in that case.
        if (connect)

       {

          kernResult = IOConnectMethodStructureIStructureO
(connect,  //

connection handle returned from IOServiceOpen().

kCoreDoRead,          // an

index to the function in the kernel.

structSizeIn,          // the

number of scalar parameters.

                                            &structSizeOut,

                                            &sampleStructIn,

                                            &sampleStructOut

                                            );

        }

   return kernResult;

}

/***************User client **************************/

getTargetAndMethodForIndex(IOService ** target, UInt32 index)

{

  { // kCoreDoRead

            NULL,

            (IOMethod)
&com_CoreSnap_UserClient::CoreSnapUserClientDoRead,

            kIOUCStructIStructO,

            sizeof(MySampleStruct),

            sizeof(MySampleStruct)

  },

}
IOReturn com_CoreSnap_UserClient::CoreSnapUserClientDoRead
(MySampleStruct

*InStruct, IOByteCount InStructSize, MySampleStruct *OutStruct,
IOByteCount

*OutStructSize)

{

    IOMemoryDescriptor *ReadBuffer = NULL;

        // Constructing memory descriptor for out put structure

     ReadBuffer = IOMemoryDescriptor::withAddress((vm_address_t)

OutStruct->buff, (IOByteCount) OutStruct->size, kIODirectionIn,
fTask);
  if(ReadBuffer) //Created IOMemoryDescriptor for buff
Successfully....

  {

    retRead = ReadBuffer->prepare();

        IOLog("\n address of prepare buffer = %p\n", retRead);
            if(retRead == kIOReturnSuccess)

            {

            IOLog("map successful\n");

            // get the provider for our userclient and call driver
read

routine

            UCProvider = OSDynamicCast(com_CoreSnap_driver,
fProvider);

            IOLog("\n UCProvider = %p\n", UCProvider);
            IOStorageCompletion completion;

            // calling driver read call by passing
IOMemoryDescriptor buffer
            if(retRead == kIOReturnSuccess)

            {

                  IOLog("\n CoreSnapDriverDoRead of Driver
Succeded...\n");

                  //return retRead;

            }

        }// end of prepare

  }

        ReadBuffer->complete();

        ReadBuffer->release();
   if (kIOReturnSuccess != retRead)

    {

            IOLog("%s[%p]::%s - returning err 0x%08x", getName(),
this,

__FUNCTION__, retRead);

    }

     fProvider->release();
    return retRead;

}

 /********************************Driver Read routine

***************************/

// kCoreDoRead

IOReturn com_CoreSnap_driver::CoreSnapDriverDoRead(IOService*
client, UInt64

byteStart, IOMemoryDescriptor * OutBuffer, IOStorageCompletion
completion)

{

    IOReturn retDrRead = kIOReturnSuccess;
    IOLog("com_CoreSnap_driver::read BEFORE **** readBytes = %lu
byteStart =

%lu \

            bufLength = %lu buffer = %s ***\n", (long)readBytes,

(long)byteStart, (long)bufLength, myBuff);
    IOLog("com_CoreSnap_driver::***AFTER::readBytes = %lu byteStart
= %lu

bufLength = %lu buffer = %s \n", (long)readBytes, (long)byteStart,

(long)bufLength, myBuff);

We are able to prepare() and map() IOMemoryDescriptor successfully
and pass

this buffer to driver's read routine(we also have interchange the
prepare

and map). My problem is while debugging it prints all the IOLogs
before

driver's standard read() method, but IOLogs after  read()  does not
get

printed in system.logs.
Are we following correct steps for reading the buffer from disk and
passing

it to user space application?

 _______________________________________________

Do not post admin requests to the list. They will be ignored.

Darwin-kernel mailing list      (Darwin-kernel@lists.apple.com)

Help/Unsubscribe/Update your Subscription:

http://lists.apple.com/mailman/options/darwin-kernel/markarian%
40apple.com
This email sent to site_archiver@lists.apple.com

Re: Read through Filter Scheme Driver

Dan Markarian