Stop SSD from waiting for "Spinning up disk..."

[Jeff Chua]

There's no need to wait for disk spin-up for USB SSD devices. This 
patch allow the SSD to skip waiting disk spin-up by passing sd_mod.ssd=1 
during boot-up.

If there's a better way to handle this, please share.


Thanks,
Jeff

--- linux/drivers/scsi/sd.c	2015-05-25 07:29:44.000000000 +0800
+++ linux/drivers/scsi/sd.c	2015-06-19 22:17:35.000000000 +0800
@@ -92,6 +92,9 @@
    MODULE_ALIAS_SCSI_DEVICE(TYPE_MOD);
    MODULE_ALIAS_SCSI_DEVICE(TYPE_RBC);

+static int ssd = 0;
+module_param(ssd, int, 0);
+
    #if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
    #define SD_MINORS	16
    #else
@@ -2738,7 +2741,9 @@
    		goto out;
    	}

-	sd_spinup_disk(sdkp);
+	sd_printk(KERN_NOTICE, sdkp, "ssd %s\n", ssd == 0 ? "off" : "on");
+	if(!ssd)
+		sd_spinup_disk(sdkp);

    	/*
    	 * Without media there is no reason to ask; moreover, some devices
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