Re: Writing to disk using filter scheme driver

4 Apr 2005

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Hi Dan,

I have make some changes in my code as follows.
UserkernelShared.h includes the following structure.
typedef struct  MySampleStruct
{
  UInt32 size;
  char* buff;
} MySampleStruct;

// these are the User Client method names
enum
{
    kMyUserClientOpen,
    kMyUserClientClose,
    kMyDoWrite,
    kMyDoRead,
    kMyNumberOfMethods
};
In main function of userspace application i am calling the MyDoWrite
function as follows
kernResult = MyDoWrite(dataPort);
if (kernResult != KERN_SUCCESS)
{
     printf("\n kMyDoWrite returned %d\n", kernResult);
     fflush(stdout);
}
The definition of MyDoWrite is as follows.
MyDoWrite(io_connect_t connect)
{   kern_return_t     kernResult;
    MySampleStruct    sampleStruct;
    char *buf;
    UInt32 size;
    size = kBufSize; //kBufSize = 512
    buf = malloc(sizeof(char) * kBufSize);
    bzero(buf, sizeof(char) * kBufSize);
    strcpy(buf, "Hello MAC.OS.X");
    sampleStruct.size = size;
    sampleStruct.buff = buf;

    IOByteCount structSize = sizeof(MySampleStruct);

    if (!connect)    {
        return kIOReturnNoDevice;
    }
    else    {        kernResult =
			IOConnectMethodScalarIStructureI(connect,
                                            kMyDoWrite,
                                            0,
                                            structSize,
                                            &sampleStruct
                                            );
    }
    if (kernResult == kIOReturnSuccess)
    {
        printf("\n kMyDoWrite was successful..........\n");
    }
    return kernResult;
}
My Userclient.h includes the following code.
class com_MySoftwareCompany_MyUserClient : public IOUserClient //derived
from IOUserClient

IOService*                  fProvider; //previously i was mentioned
					//com_MySoftwareCompany_driver_MyFilterSchemeheme

My Userclient.cpp includes the following code.
IOExternalMethod *
com_MySoftwareCompany_MyUserClient::getTargetAndMethodForIndex(IOService
** target, UInt32 index)
{
       { // kMyDoWrite
            NULL,
            (IOMethod) &com_MySoftwareCompany_MyUserClient::myDoWrite,
            kIOUCScalarIStructI,
            0,
            sizeof(MySampleStruct)
       },*/
}

IOReturn com_MySoftwareCompany_MyUserClient::myDoWrite(MySampleStruct *
vInStruct, UInt32 * structSize)
{   IOReturn retWrite = kIOReturnSuccess;
    char *buf;
    UInt32 Size;
    IOService* ffProvider;
    memset(buf, 0x0, 512);
    buf = vInStruct->buff;
    Size = vInStruct->size;

   if ( *structSize != sizeof(MySampleStruct))
                    return kIOReturnBadArgument;

     if (fProvider && !isInactive())
    {
          IOMemoryDescriptor *mem = IOMemoryDescriptor::withAddress(buf,
Size, kIODirectionOut, fTask);
          if (mem)
          {
                retWrite = mem->prepare();
                if(kIOReturnSuccess == retWrite)
                {
                   ffProvider =
OSDynamicCast(com_MySoftwareCompany_driver_MyFilterScheme, fProvider);
// is this a correct way of casting???

                    if (!ffProvider)
                    {
                           return false;
                    }
                    else
                    {
        		   //retWrite = ffProvider->write(provider, 512, mem,
completion);
                            retWrite = ffProvider->DoDriverWrite(mem);
                    }
                }
		mem->complete();
                mem->release();
          }
          else
          {
               retWrite = kIOReturnNoMemory;
          }
          release();
    }
    else
    {
         retWrite = kIOReturnNotAttached;
    }

    if (kIOReturnSuccess != retWrite)
    {
        IOLog("\n myDoWrite returned = %d\n", retWrite);
    }

    return retWrite;
}

But i am still facing the same problem that "no matching function
IOService::DoDriverWrite()"

And if i have to call driver routine from my userclient how should i
call them???

Thanks in Advance,
Yogesh Pahilwan

On Thu, 2005-03-31 at 02:44, Dan Markarian wrote:
...
Hi Parav,
I believe I see the disconnect.  I saw MySampleStruct and was under
the impression that MySampleStruct is what carries the "buf" address
and the "buf" size into the kernel.  It seems, rather, that it passes
the "buf" address and "buf" size as a variable-size structure across
the user client interface.  You might wish to note that technique is
limited to 4 kB, I believe, and does involve a copy across the kernel
boundary.  I am not sure what the problem is though offhand.  It
might be one of:
...
...
size = kBufSize;
size = 1024;
...
...
bzero(buf, sizeof(char) * 1048576);
bzero(buf, sizeof(char) * 1024);
...
...
IOMemoryDescriptor *mem = IOMemoryDescriptor::withAddress(buf,
1024,
kIODirectionOut);
IOMemoryDescriptor *mem = IOMemoryDescriptor::withAddress(buf,
size,
kIODirectionOut);
Dan
On 30 Mar 2005, at 12:44 PM, Parav Pandit wrote:
...
...
com_MySoftwareCompany_driver_MyFilterScheme*        fProvider;
I am sorry, I haven't look the code properly.
you have fProvider of your filterScheme class.
fTask would tell to map in kernel userClient context for calling
task - fTask but than how this would solve the problem of calling
the driver function?
Please help me to understand.
fTask is the application task which has made the code to driver. is
this correct?
We need to share memory between kernel task and user space, so why
to give fTask rather than kernel_task?
I couldn't find the answer from the Writing custom user client
docuement.
Regards,
Parav Pandit
Dan Markarian <markarian@apple.com> wrote:
Hi Yogesh,
...
IOMemoryDescriptor *mem = IOMemoryDescriptor::withAddress(buf,
1024, kIODirectionOut);
IOMemoryDescriptor *mem = IOMemoryDescriptor::withAddress(buf,
1024, kIODirectionOut, fTask);
Dan
On 30 Mar 2005, at 7:54 AM, Yogesh P wrote:
...
Hi folks,
I have written a filter scheme driver,userclient and userspace
application tool for doing read/write operations on IOMedia
partitions.
I have successfully send a structure from userspace to kernelspace
through userclient.But when i try to read/write a buffer from
userspace
to kernel space,i am not able to map userspace buffer to kernel
address
space.
I am specifying my code here.
UserkernelShared.h includes the following structure.
typedef struct MySampleStruct
! { UInt32 size;
void* buff;
} MySampleStruct;
In main function of userspace application i am calling the
SPSOFT_Write
function as follows.
char *buf;
UInt32 size;
size = kBufSize;
buf = malloc(sizeof(char) * 1024);
bzero(buf, sizeof(char) * 1048576);
strcpy(buf, " Hello MACOSX");
I want to write this "buf" to the disk through userclient.
// This shows an example of calling a user client's open method.
kernResult = MyDoWrite(dataPort, buf, size);
if (kernResult != KERN_SUCCESS)
{ printf("\n kMyDoWrite returned %d\n", kernResult);
// This closes the connection to our user client and destroys the
connect handle.
IOServiceClose(dataPort);
return 0;
}
The definition of MyDoWrite is as follows.
kern_return_t
MyDoWrite(io_connect_t connect, void *buf, UInt32 size)
{ kern_return_t kernResult;
if (!connect){
return kIOReturnNoDevice;
}
else {
kernResult = IOConnectMethodScalarIStructureI(connect,
kMyDoWrite,
0,
size,
buf
);
}
if (kernResult == kIOReturnSuccess){
printf("\n kMyDoWrite was successful..........\n");
}
return kernResult;
}
My Userclient.h and Userclient.cpp includes the following code.
com_MySoftwareCompany_driver_MyFilterScheme* fProvider;
IOExternalMethod *
com_MySoftwareCompany_MyUserClient::getTargetAndMethodForIndex
(IOService
** target, UInt32 index)
{
{ // kMyDoWrite
NULL,
(IOMethod) &com_MySoftwareCompany_MyUserClient::myDoWrite,
kIOUCScalarIStructI,
0,
0xffffffff
},
}
IOReturn com_MySoftwareCompany_MyUserClient::myDoWrite(void* buf,
UInt32
size)
{ IOReturn retWrite = kIOReturnSuccess;
UInt32 Size = size;
if (fProvider && !isInactive()){
IOMemoryDescriptor *mem = IOMemoryDescriptor::withAddress(buf,
1024,
kIODirectionOut);
if (mem){
retWrite = mem->prepare();
if(kIOReturnSuccess == retWrite){
retWrite = fProvider->myDoWrite
(mem,Size); //when i
call this driver function it gives me the error as
IOService::fProvider
has no function myDoWrite.
}
mem->complete();
mem->release();
}else{
retWrite = kIOReturnNoMemory;
}
release();
}
How should i call the filter scheme driver read/write routines
from my
userclient?? Or is there any sample code of read/write for filter
scheme
driver???
Any help, certainly help me in solving this problem.
Thanks! in advance.
Yogesh Pahilwan
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