Block device driver: How to handle hardware failure

[beck0778@xxxxxxx]

Hello,

I am writing a block device driver to access Secure Digital (SD) cards over 
an SPI interface for an embedded (ppc) product.

If the SD card is removed while it is still mounted, the kernel will 
continue to generate read and write requests for the driver, which it 
obviously can't perform successfully. I am wondering how to tell the kernel 
that this device is no longer available, and to cancel all pending 
requests. Should I un-register my gendisk from inside the request handler? 
Is there a way to clear out the queue and close down the device?

I have loosely based my driver on the 'sbull' driver outlined in "Linux 
Device Drivers", by Corbet, Rubini, and Kroah-Hartman, using the simplest 
possible, synchronous request handler. I have attached some pseudo-code for 
that at the end of this message.

Thanks in advance for any recomendations,

Matthew


=== Pseudo-code for request handler: ===

static void sdcard_request(request_queue_t *q)
{
  struct request *req;
  while ((req = elv_next_request(q)) != NULL)
  {
     if (!blk_fs_request(req))
     {
        //printk (KERN_DEBUG "Skipping non-fs request\n");
        end_request(req, 0);
        continue;
     }

     if (!SD_Card_Present())
     {
        //somehow handle the missing card?
     }

     if (rq_data_dir(req))
     {
        //write data to sd card
     }
     else
     {
        //read data from sd card
     }
  }
}

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