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Re: oskit-mach: device_write

From: Daniel Wagner
Subject: Re: oskit-mach: device_write
Date: Sun, 3 Mar 2002 18:08:23 +0100
User-agent: Mutt/1.3.24i

The bug is triggered, when from an underlying layer (driver layer, I think) 
an error via the return value is reported. I tried several values for the
size parameter. If it's reasonable large, for example 64 bytes, the system
stays stable. But count = 4 will trigger the bug. To be on sure side I tried
hacked following into oskit-mach/oskit/ds_routines:

ds_device_write (device_t dev, ipc_port_t reply_port,
                 mach_msg_type_name_t reply_port_type, dev_mode_t mode,
                 recnum_t recnum, io_buf_ptr_t data, unsigned int count,
                 int *bytes_written)
          vm_offset_t addr;
          kern_return_t kr = vm_map_copyout (device_io_map, &addr,
                                             (vm_map_copy_t) data);
          if (kr == KERN_SUCCESS)
              /* Note: we assume that write_inband can take a large count.  */
              kr = (*dev->ops->write_inband) (dev, reply_port,
                                              reply_port_type, mode, recnum,
                                              (char *) addr, count,
              (void) vm_deallocate (device_io_map, addr, count);
          if (count == 66) /* XXX */
            return 123;
          return kr; 

As you can see, if count is 66, the return value is just a silly value. 
Without these lines, the kernel works fine. The question now is, why
an error code is not a good thing at this location? 


Daniel Wagner                              "use quit to exit"
email: wagi@gmx.ch

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