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Darwin 0.2 Driver Kit

			notes for IODisk presentation
			
IODevAndIdInfo usage

* Declared in disk driver's kernel glue layer
* Fields:
  * rawDev, blockDev:
    * init'd:
      * in dev-specific routine in kernel glue layer (e.g., 
        sd_init_idmap(), called from SCSIDisk's +initialize)
    * Used: 
      * for volCheck communication (needed for insertion/automount)
  
  * id's 
    * init'd: 
      * in -registerUnixDisk (in mk/driverkit/kernselDiskMethods,
  	called from IODiskPartition +probe, for both physical disk and all
  	valid IODiskPartition instances). 
    * Used:
      * in kernel glue layer, to convert dev_t to id
  
* IODisk instances have pointer to associated IODevAndIdInfo. 
  * init'd by -setDevAndIdInfo
    * in dev-specific +probe for physical disks
    * in -connectToPhysicalDisk for all logical disks (it's set to phys
      disk's IODevAndIdInfo)
      
  * used: 
    * connectToPhysicalDisk, to get physicalDisk's struct
    * {register,unregister}UnixDisk
    * Calls from IODisk to volCheckRegister()
    
* Protocols to be implemented by disk drivers

  @protocol IODiskReadingAndWriting
  
  - (IOReturn) readAt		: (unsigned)offset 
				  length : (unsigned)length 
				  buffer : (unsigned char *)buffer
				  actualLength : (unsigned *)actualLength 
				  client : (vm_task_t)client;

  - (IOReturn) readAsyncAt	: (unsigned)offset 
				  length : (unsigned)length 
				  buffer : (unsigned char *)buffer
				  pending : (void *)pending
				  client : (vm_task_t)client;
		
  - (IOReturn) writeAt		: (unsigned)offset 
				  length : (unsigned)length 
				  buffer : (unsigned char *)buffer
				  actualLength : (unsigned *)actualLength 
				  client : (vm_task_t)client;
		  
  - (IOReturn) writeAsyncAt	: (unsigned)offset 
				  length : (unsigned)length 
				  buffer : (unsigned char *)buffer
				  pending : (void *)pending
				  client : (vm_task_t)client;
  @end
  
  @protocol IOPhysicalDiskMethods

  /* called when volCheck or IODiskPartition knows that something
     has changed which driver should be aware of.
     e.g.: setFormatted, disk insertion detect, transition to ready. */
     
  - (IOReturn)updatePhysicalParameters;
  
  /* called by volCheck per user input on insert request panel */
  
  - (void)abortRequest;
  
  /* called by volCheck when transition to ready is detected. Wakes up 
     I/O threads which are waiting for disk. */
     
  - (void)diskBecameReady;
  
  /* ensures disk is present/ready, with alert panel if necessary. Called
    by clients before doing r/w. */
    
  - (IOReturn)isDiskReady	: (BOOL)prompt;
  
  - (IOReturn) ejectPhysical;	
  
  /* Used by volCheck (mostly) and at probe time by IODiskPartition. */
  - (IODiskReadyState)updateReadyState;

  @end

.........................................

Outline:

1. Intro
   -- class hierarchy - draw it
   -- leaf classes just know how to read, write, eject, sense status
   -- IODiskPartition takes care of disk labels, partitions
   -- volCheck module takes care of polling for ready and panel requests
   
2. volCheck module functions: 
   -- insertion detection
   -- alert panels
   -- abort notification
   
   Discuss briefly the IPC between vol and WS. 
   
3. IODiskReadingAndWriting protocol
   -- briefly mention 'pending', more to come...
   
4. IOPhysicalDiskMethods protocol

5. kernel glue layer

   Start with IODevAndIdInfo. 
   
6. I/O thread architecture, incl. I/O queues

7. Q&A

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